tag:blogger.com,1999:blog-21798416184513345472024-03-15T21:10:09.300-04:00Test Happens - Teledyne LeCroy BlogTest Happens.Jofadudehttp://www.blogger.com/profile/10288159623378582877noreply@blogger.comBlogger371125tag:blogger.com,1999:blog-2179841618451334547.post-22536155521831294282023-02-27T08:00:00.025-05:002023-05-16T16:01:32.660-04:00The Case for CAN XL in 10 Mbit/S In-vehicle Networks<p>CAN XL has recently emerged as a contender in the 10 Mbit/S in-vehicle network space, along with 10Base-T1S Automotive Ethernet. What does CAN XL bring to earn its place on the vehicle bus?</p><p>CAN XL builds upon the foundation of CAN and CAN FD, both protocols with a long history in the automotive industry. Figure 1 summarizes the characteristics of the three CAN variants.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjy9wEXifxY3BUbTDGm0ZydKn10QhP0tNYhV8KrPbOSKwWyvozj7U3Ow0ZgrxenKvYh_ViLc_jl1MqZ_mP7Re0w6ueAtmmzVHGJlknX7KG21bX6IvHor6zkMsQKAaUdWsqhGtmhWRgurv9ifOtGGB39T-5o4HoKJU4M0bKTNaM9G2GXntsdsbCKVXWPnQ/s2009/CAN-table.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="965" data-original-width="2009" height="308" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjy9wEXifxY3BUbTDGm0ZydKn10QhP0tNYhV8KrPbOSKwWyvozj7U3Ow0ZgrxenKvYh_ViLc_jl1MqZ_mP7Re0w6ueAtmmzVHGJlknX7KG21bX6IvHor6zkMsQKAaUdWsqhGtmhWRgurv9ifOtGGB39T-5o4HoKJU4M0bKTNaM9G2GXntsdsbCKVXWPnQ/w640-h308/CAN-table.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. A comparison of the characteristics of CAN, CAN FD and CAN XL.</span></td></tr></tbody></table><p>CAN XL increases throughput with a Fast Mode bit rate of 20 Mbit/S in the data phase, while it operates at 1 Mbps in the arbitration phase (those fields other than data). Another feature contributing to the improved bandwidth of CAN XL is the increased data field maximum length of 2048 bytes compared to 64 bytes for CAN FD and 8 bytes for classic CAN.<span></span></p><a name='more'></a><p></p><p>All three CAN variants use Non-Return-to-Zero (NRZ) encoding. This means there can be long intervals where there are no edges in the data, which poses a problem for clock recovery where periodic edges are needed to “lock on” and synchronize to the data. CAN and CAN FD use a method called stuff bits to assure that clock edges are available. Older CAN formats use dynamic bit stuffing, where if five bits are transmitted with the same logical state, a stuff bit of the opposite logical state is added to the data stream. CAN XL uses dynamic bit stuffing in the arbitration fields. In the data field, which operates at a higher clock rate, CAN XL uses fixed bit stuffing after every ten bits. Because we can predict the length of the data field with a fixed stuff bit period, data interpretation is faster, a benefit at the higher data rate of CAN XL.</p><p>The frame format in CAN XL has also been lengthened and improved to allow greater flexibility. Where CAN and CAN FD have the identifier in the arbitration field, which plays a role in the arbitration of priority, CAN XL now has an 11-bit field called Priority ID, which handles priority only. Addressing is handled by another method in the control field.</p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEibXxdqRWwJdEcpteOzdiTpZRU3_2pMidbY6D2PjAMcWVSRN5JZERwS4BfXfkE_nxzCyBcx9zWDzUfz1BLsYab8JOBVgIGaGNBnaYQc-g0xilGNSYB-4IHj1gJJ2442WNJmh5CP8djH3U1t0dyFvBA-FybRndW_p3DhihT885t1SiYsguKOxeYO90LsRQ/s847/CAN-daisy-chain.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto; text-align: center;"><img border="0" data-original-height="847" data-original-width="498" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEibXxdqRWwJdEcpteOzdiTpZRU3_2pMidbY6D2PjAMcWVSRN5JZERwS4BfXfkE_nxzCyBcx9zWDzUfz1BLsYab8JOBVgIGaGNBnaYQc-g0xilGNSYB-4IHj1gJJ2442WNJmh5CP8djH3U1t0dyFvBA-FybRndW_p3DhihT885t1SiYsguKOxeYO90LsRQ/s320/CAN-daisy-chain.PNG" width="188" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><p align="left" class="MsoCaption" style="text-align: left;">Figure <!--[if supportFields]><span
style='mso-element:field-begin'></span><span
style='mso-spacerun:yes'> </span>SEQ Figure \* ARABIC <span style='mso-element:
field-separator'></span><![endif]-->7<!--[if supportFields]><span
style='mso-no-proof:yes'><span style='mso-element:field-end'></span></span><![endif]-->.
The CAN “Daisy Chain”<br />topology is very scalable, with as <br />many new nodes as
needed easily added.<o:p></o:p></p></td></tr></tbody></table><p>CAN utilizes a Daisy Chain network topology, where devices are connected to a central bus with varying length stubs. CAN XL allows stubs to be up-to-one meter in length. A major advantage of CAN XL, which applies to all the CAN variants, is that this topology is easily scalable. Modifying an existing system involves simply adding CAN network devices with distinct IDs to the bus. </p><p></p><p>Also common to all versions of CAN is the use of dominant and recessive states to signal priority. The dominant state is the higher differential voltage state. The recessive state is the lower differential voltage state.</p><p>The bus driver is capable of actively driving the bus to the dominant state, while the return to the recessive state depends on resistive discharge through the terminations. This arrangement of using the dominant and recessive states allows other nodes to override bits, thereby defining the priority of the different IDs. If a node is sending dominant zeros, then the other nodes know that ID has a higher priority. Overriding bits are also used in the acknowledgment field to indicate the status of received data.</p><p>But this technique has a big disadvantage, especially at higher speeds, because only the dominant state is really driven. The recessive state has only passive resistors to pull signal to the recessive voltage level. If there is an impedance mismatch on the bus, it is possible to see a lot of reflections, which can result in ringing. At lower speeds it is not an issue, because the settling point can be defined in CAN and the sampling point set at a time where it is easy to detect a 1 versus a 0. At higher speeds, however (e.g., above 2 Mbit/S), it is nearly impossible to detect a 1 versus a 0 in the presence of reflections. </p><p>To improve signal fidelity, CAN XL implements a new Fast Mode. In Fast Mode, both logic states are driven symmetrically, and the receiver threshold is set to 0 volts differential with a tolerance of ±100 mV. When the device switches from the arbitration phase to Fast Mode for the data phase, there a change in the amplitude and in the offset. There is also a change in impedance as both states are driven from a low impedance source. Because both states are driven, they are described in terms of 1 and 0 levels, similar to other standards, rather than dominant/recessive. There is much less ringing and a better margin for the receiver to detect a 1 versus a 0. Fast Mode is applied only to the data phase of the CAN XL frame, as shown in Figure 3.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHgF8IqQi67E_f3Zd0dWeQhKZ7NUU8h7ZsIavcSTpNR1iS_YCt4FDsiYLDQk3LwagydPZG71KMJfK1I4IBjnJuMVhuH6b-azskvCwuvRpGI9F-SeCawWwOjipqSTyZH-ITSzvdQgVmt1nUSNkqx6frj67oeailH5KZ2dvfKxmf2NMipKEKKjThk6wgCg/s1911/CANXL-frame.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="754" data-original-width="1911" height="252" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHgF8IqQi67E_f3Zd0dWeQhKZ7NUU8h7ZsIavcSTpNR1iS_YCt4FDsiYLDQk3LwagydPZG71KMJfK1I4IBjnJuMVhuH6b-azskvCwuvRpGI9F-SeCawWwOjipqSTyZH-ITSzvdQgVmt1nUSNkqx6frj67oeailH5KZ2dvfKxmf2NMipKEKKjThk6wgCg/w640-h252/CANXL-frame.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. Fast Mode is applied to the high-speed data phase of a CAN XL frame to enhance signal integrity.</span></td></tr></tbody></table><p>The selection of one bus protocol over another when designing an IVN depends on many things. Certainly, if previous designs already use CAN and CAN FD, then it may be easier to simply extend them using CAN XL rather than switch to another protocol. For example, many specialty vehicles (e.g., fire trucks) are customizations of a standard base design. If CAN is already used in the basic vehicle, it will likely be implemented for any new functionality that is added during customization.</p><p>Even some functions that normally require higher speed data, such as cameras for ADAS, can be accomplished using CAN XL. For example, in lower cost vehicles that do not utilize high-speed data links, CAN XL adds capabilities like support for compressed video, which can be used for back up cameras. </p><p>For these and other reasons, CAN is likely to be with us for quite some time, even if the trend in automotive design is toward a single-network vehicle architecture. Learn more in our free, on-demand webinar, <a href="https://go.teledynelecroy.com/l/48392/2022-10-25/8l8fk9?&utm_source=website&utm_medium=blog&utm_campaign=22-11-08-fundamentals-of-10-mpbs-ivn" target="_blank"><i>Fundamentals of 10 Mb/s In-vehicle Networks</i></a>.</p><div><div>Our <a href="https://www.teledynelecroy.com/options/productseries.aspx?mseries=696&groupid=88" target="_blank">CAN XL TDME</a> serial trigger and decode option for Teledyne LeCroy oscilloscopes decodes all major CAN protocols—Standard CAN, CAN FD and CAN XL. Symbolic decoding supporting .dbc or AutoSAR .arxml symbol files is available. </div><h4>Also see:</h4><div><a href="https://blog.teledynelecroy.com/2018/05/debugging-canbus-for-iot-devices.html" target="_blank">Debugging CANbus For IoT Devices</a></div><div><br /></div></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-65815659602122458682023-02-20T08:00:00.001-05:002023-02-20T08:00:00.173-05:00The Evolution of In-vehicle Network Architectures<p>The drive for fuel-efficient and safer vehicles opened the door to electronic control in vehicles, which in turn led to the deployment of In-vehicle Networks (IVN). IVNs have become the backbone of modern vehicles. The volume of data flowing through these networks is increasing exponentially with demands for electric vehicles, advanced driver assistance systems (ADAS), radar, lidar, infotainment systems, cameras and vehicle-to-vehicle communications systems. </p><p>To meet this need, the automotive industry—working with technology suppliers—has developed specialized communications protocols and application-specific extensions to existing network technologies, standardized under the aegis of organizations like ISO and IEEE, and it continues to investigate new topologies and protocols to improve performance, increase reliability and lower the costs of IVNs. Two recent developments have filled a longstanding gap in IVN architectures: CAN XL (up-to-20 Mbit/S extended length CAN) and 10Base-T1S (10 Mbit/S single-pair Ethernet), both of which operate in the 10 Mbit/S network space. What problems do these protocols solve and what opportunities do they present for IVN design?<span></span></p><a name='more'></a><p></p><p>IVNs are organized by a composite architecture combining multiple networks in some logical organization. </p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIiwPX3g8hMgF_b9HDk_ovtLzvjZSVRBfF1qjVZMQHOfXW1bT3UcqXgRmM1h3_EJT4pFB4r3YUykEWvzjvnDYOoL4BhliW9OU6dMK4Y2LrOdV5LH7hICln7sKm68lVPh_qrow2-v5hwL1nqKqB2gI8r8O28bu2D_YUv31mGSS-D4tuOsQjUUoxGEU0pw/s1169/Classic-IVN.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="534" data-original-width="1169" height="183" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIiwPX3g8hMgF_b9HDk_ovtLzvjZSVRBfF1qjVZMQHOfXW1bT3UcqXgRmM1h3_EJT4pFB4r3YUykEWvzjvnDYOoL4BhliW9OU6dMK4Y2LrOdV5LH7hICln7sKm68lVPh_qrow2-v5hwL1nqKqB2gI8r8O28bu2D_YUv31mGSS-D4tuOsQjUUoxGEU0pw/w400-h183/Classic-IVN.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. In the Classic IVN architecture, different functional networks utilizing different topologies,<br /> protocols and data rates are connected to each other.</span></td></tr></tbody></table><p>In the Classic architecture, different Engine Control Units (ECUs) all in different locations in the vehicle are connected to each other. Normally, they are placed near to the sensors or the motor depending on the function of the ECU. The result is that everything in the IVN is connected by a huge, heavy and costly cable set.</p><p>If we look at the history of IVN protocols used by these ECUs (Figure 2), until recently the pattern shows a concentration of data rates at the low end (under 1 Mbit/S) and at the high end (over 100 Mbit/S). Only FlexRay stood in the mid-range 10 Mbit/S space, and while its characteristic Star topology is very flexible and scalable, FlexRay tends to be more expensive to implement than other automotive protocols, limiting its adoption.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqlzn0Xn4Cl00I-QTqRSNUjl4qMlijHh4FzwfWD0AQldTsR3f7nZ1CxN2wptTQFWe9bKaFjZFm1UDfFQjph8pCyvC_D8FaWTwKwKGOtpgcyqf2ja5HCaRGF3m_Wm-kW4x5nXClTDIKe5WwdNWrkoQDyNhvIqCUTCkCPXGqlCc1MsBrIMIuYrWEKQzI-A/s1379/IVN-protocols.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="619" data-original-width="1379" height="288" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqlzn0Xn4Cl00I-QTqRSNUjl4qMlijHh4FzwfWD0AQldTsR3f7nZ1CxN2wptTQFWe9bKaFjZFm1UDfFQjph8pCyvC_D8FaWTwKwKGOtpgcyqf2ja5HCaRGF3m_Wm-kW4x5nXClTDIKe5WwdNWrkoQDyNhvIqCUTCkCPXGqlCc1MsBrIMIuYrWEKQzI-A/w640-h288/IVN-protocols.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. The history of IVN protocols sorted by data rate. Until recently there was a gap between 1 and 100 Mbps.</span></td></tr></tbody></table><p>The number of electronic control units (ECUs) in vehicles is continuing to rise. A current mid-range vehicle might have 70 ECUs, while a luxury vehicle might have as many as 150. Connecting these devices is challenging, and vehicle manufacturers seek to consolidate capabilities into fewer devices to reduce complexity and cost. Hence, the evolution of the Domain architecture currently used in newer vehicles.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCTw6DlPI3cfHcKqenFaBHlXYiwpOC3mv7y7Z82zjY8IEfDP8ug7ip_Ln4mZfhr3vQGoGH10XpcV--AF5RbYnhlCiUv1kS5jG_XTFNTl5hYgUhIWVyqFq6woeBZbwwrwoGaGPHsCPpAx2UTi5LibqUTVjN9T1arKlSiT0jV2W-EzZmsPm6rNruOaWagw/s1150/Domain-IVN.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="566" data-original-width="1150" height="196" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCTw6DlPI3cfHcKqenFaBHlXYiwpOC3mv7y7Z82zjY8IEfDP8ug7ip_Ln4mZfhr3vQGoGH10XpcV--AF5RbYnhlCiUv1kS5jG_XTFNTl5hYgUhIWVyqFq6woeBZbwwrwoGaGPHsCPpAx2UTi5LibqUTVjN9T1arKlSiT0jV2W-EzZmsPm6rNruOaWagw/w400-h196/Domain-IVN.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. In the Domain IVN architecture, domain controllers organize the ECUs under them and<br /> communicate with each other through “gateways”.</span></td></tr></tbody></table><p>The ECUs are more centralized and are divided into functional groups or “domains”. For example, there is one domain for infotainment functions, another domain for the drivetrain, etc., all connected to each other through a gateway. The different domains may use different physical layers, which means different bus systems. Some may use Ethernet while others use CAN. The gateway handles translation between the different domains and ensures smooth, safe and correct communication between all ECUs.</p><p>The “next generation” IVN architecture is called Zonal architecture. In the Zonal architecture, main controllers called zone controllers are located in different sections of the car (e.g., front left, front right). The sensors and actuators are connected directly to the zone controller, and because the zone controller is close to the interfaced devices, the cable lengths required to connect them are relatively short, resulting in less weight and expense. This architecture reduces the number of wires in the harness, and there are fewer ECUs overall replaced by much more powerful, centralized ECUs for the different regions of the car.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUJwk7yP4OhOOzcwA1szr8pS-MVMSHbRS4A-EEKT0xDqeePp2PUKjIhEzMhQF95sRJpFnMA2-HCiplyRkenC0YTVZtTSvgOKJt2jdqGtrsOMfLiMtQQlml-8gMvPP7PPXhv9CXkyyh25H60D3y4bQPqoGYDnWeuA5W31mnjMLfMKhotUkkFJSpyBk84w/s1153/Zonal-IVN.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="535" data-original-width="1153" height="185" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUJwk7yP4OhOOzcwA1szr8pS-MVMSHbRS4A-EEKT0xDqeePp2PUKjIhEzMhQF95sRJpFnMA2-HCiplyRkenC0YTVZtTSvgOKJt2jdqGtrsOMfLiMtQQlml-8gMvPP7PPXhv9CXkyyh25H60D3y4bQPqoGYDnWeuA5W31mnjMLfMKhotUkkFJSpyBk84w/w400-h185/Zonal-IVN.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. In the Zonal INV architecture, Zone controllers organize the ECUs in their region, while the<br /> Zone controllers are connected to each other and a Central Controller by a high-speed “backbone”.</span></td></tr></tbody></table><p>A central controller connected to the zone controllers over a high-speed data “backbone” performs data fusion and higher level decision making functions. The backbone also serves to provide the data redundancy needed especially for autonomous driving. Because of the volume of data exchanged between the controllers, as well as the need to connect to external high-speed networks, higher speed and higher throughput are essential to this architecture, especially for the central controller and backbone functions. It is necessary to be able to move data at speeds well above 10 Mbit/S.</p><p>All IVN designs involve multiple buses because some operations do not require a high data rate and the attendant bandwidth, as shown in Figure 5. The power train or body/comfort domains are normally slower networks. In most current architectures, only a limited number of functions, like infotainment or ADAS systems, absolutely require high bandwidth. Some functions that do not need a high data rate are very important nonetheless and need a high priority. For example, safety functions require a very high priority, but only have a medium bandwidth requirement. So, for many functions, a data rate of 10 Mbit/S is as high as required. Yet, until recently, few protocols operated in the gap between 1 and 10 Mbit/S.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLBokPo7EnowElu30CxeLgsUECP6WHKfjvm7hhM3JUVQPFutBEkreYPJBtTFtv5WnU1L8IhNqUammMUlfGnOdzg3U5IYaJUC6pgMB1aHhmUeGl7eiWawx9VUCQC6zKEbmMDCFsqRxEobwRjvVnL2diR2G-aFIvDwQYJNcIPT-iYsdivSCmaaecAzTXVQ/s1330/IVN-func-req.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="320" data-original-width="1330" height="154" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLBokPo7EnowElu30CxeLgsUECP6WHKfjvm7hhM3JUVQPFutBEkreYPJBtTFtv5WnU1L8IhNqUammMUlfGnOdzg3U5IYaJUC6pgMB1aHhmUeGl7eiWawx9VUCQC6zKEbmMDCFsqRxEobwRjvVnL2diR2G-aFIvDwQYJNcIPT-iYsdivSCmaaecAzTXVQ/w640-h154/IVN-func-req.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 5. A summary of vehicular network requirements by function.</span></td></tr></tbody></table><p>CAN FD with a maximum data rate of 5 Mbit/S was an early attempt to close that gap. The more recent entries to fill the data rate gap are CAN XL (extended length CAN), which operates up to 20 Mbit/S in the data phase, and 10Base-T1S (<a href="https://teledynelecroy.com/serialdata/automotive.aspx" target="_blank">10Mbit/s single-pair Ethernet</a>), which operates at a maximum rate of 10 Mbit/S.</p><div>We'll talk more about where CAN XL and 10Base-T1S fit into 10 Mbit/S IVN design in future posts.</div><div><br /></div><div>Learn more in our free, on-demand webinar, <a href="https://go.teledynelecroy.com/l/48392/2022-10-25/8l8fk9?&utm_source=website&utm_medium=blog&utm_campaign=22-11-08-fundamentals-of-10-mpbs-ivn" target="_blank"><i>Fundamentals of 10 Mb/s In-vehicle Networks</i></a>.</div><div><br /></div><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2022/10/oscilloscope-testing-of-10base-t1s.html" target="_blank">Oscilloscope Testing of 10Base-T1S Automotive Ethernet Signal Integrity</a></div><div><a href="https://blog.teledynelecroy.com/2022/10/oscilloscope-measurements-of-10base-t1s.html" target="_blank">Oscilloscope Measurements of 10Base-T1S Automotive Ethernet PLCA Cycle Timing</a></div><div><a href="https://blog.teledynelecroy.com/2022/08/physical-layer-collision-avoidance-in.html" target="_blank">Physical-Layer Collision Avoidance in 10Base-T1S Automotive Ethernet</a></div><div><a href="https://blog.teledynelecroy.com/2021/06/automotive-ethernet-in-vehicle.html" target="_blank">Automotive Ethernet in the Vehicle</a></div><div><a href="https://blog.teledynelecroy.com/2021/06/fundamentals-of-automotive-ethernet.html" target="_blank">Fundamentals of Automotive Ethernet</a></div><div><a href="https://blog.teledynelecroy.com/2018/05/debugging-canbus-for-iot-devices.html" target="_blank">Debugging CANbus For IoT Devices</a></div><div><br /></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-57426580070507507852023-02-13T08:00:00.004-05:002023-03-16T11:19:53.162-04:00Making New PCIe 6.0 Transmitter Equalization Measurements with Your Oscilloscope<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghZIM2e3zzbjQW2dnAj_xFeW6ok2Fpiy4_2mvVpeskXvRx7oRfZgdNk5gRwIuC8X3RgniMEdIqgvbIPR_2vvdS1Uw7oEGskv7o1jwkDCM2Ttlzhi6YTWDZ93lTmeRo1J2KtnBkUYZhrZXP4y8DH65Kp-1rFXAj_3_BqGHj3gpwnw5v-5tQzWhb7JubtQ/s1275/SDA3_TxEQPulseQ1.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="770" data-original-width="1275" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghZIM2e3zzbjQW2dnAj_xFeW6ok2Fpiy4_2mvVpeskXvRx7oRfZgdNk5gRwIuC8X3RgniMEdIqgvbIPR_2vvdS1Uw7oEGskv7o1jwkDCM2Ttlzhi6YTWDZ93lTmeRo1J2KtnBkUYZhrZXP4y8DH65Kp-1rFXAj_3_BqGHj3gpwnw5v-5tQzWhb7JubtQ/w400-h241/SDA3_TxEQPulseQ1.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. Transmitter equalization test results for preset Q1.</span></td></tr></tbody></table><p>PCI Express® 6.0 achieves its 64-GT/s data rate, double that of PCIe® 5.0, by moving from non-return-to-zero (NRZ) signaling to four-level pulse-amplitude-modulation (PAM4) signaling. This results in the need for more complex algorithms for voltage and timing measurements.</p><p>The latest release of SDAIII software for Teledyne LeCroy oscilloscopes lets you easily measure response at different transmitter equalization presets to confirm that Tx EQ is achieving the specified levels prior to taking your DUT for compliance testing. The Tx EQ measurement feature works with NRZ signals and, if you have the additional <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=691&groupid=103" target="_blank">SDAIII-PAMx</a> option, with PAM3 and PAM4 signals, too.</p><h3 style="text-align: left;">Transmitter Equalization Coefficients and Presets Measurement</h3><p>In PCIe 6.0, transmitter equalization measurements are performed on the new PAM4 Compliance Pattern signal using the AC method that was first introduced in PCIe 5.0.<span></span></p><a name='more'></a><p></p><p>During the measurement (Figure 2), the device under test (DUT) transmits the Compliance Pattern with the corresponding TX equalization coefficients. An oscilloscope captures this equalized Compliance Pattern, and post-processing software extracts the equalized pulse-response waveform. The DUT also transmits the Compliance Pattern with no TX equalization, which the oscilloscope captures, and the post-processing software applies TX equalization coefficients to construct an equalized pulse-response waveform. This process results in TX preset coefficients that represent the best-fit TX equalization coefficients in order to minimize the mean square error between the measured equalized pulse-response waveform and the reconstructed equalized pulse-response waveform. </p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGLdeigtHd2QN0PuEcF_T1_eWvXc2wtniUZag2-3hPtWE8qCgldXv9JZrcV-0xidY1Qeba7RKHwN6m5K6t4UNJep2_QcrHNTePXZ_vxHJEbMGW4UZ3UL9nW66pqyps2qZyx9QvU1V4tsqtt_ILfd6A0-yTtQygxujq2oc_yIiKOQADYM7hhq582UgrSw/s773/SDA3_TxEQMethodology.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="270" data-original-width="773" height="224" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGLdeigtHd2QN0PuEcF_T1_eWvXc2wtniUZag2-3hPtWE8qCgldXv9JZrcV-0xidY1Qeba7RKHwN6m5K6t4UNJep2_QcrHNTePXZ_vxHJEbMGW4UZ3UL9nW66pqyps2qZyx9QvU1V4tsqtt_ILfd6A0-yTtQygxujq2oc_yIiKOQADYM7hhq582UgrSw/w640-h224/SDA3_TxEQMethodology.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. Methodology for measuring Tx equalization coefficients and presets from the PCI Express Base Specification Revision 6.0, 16 December 2021, Figure 8-7 on page 1326. Courtesy of PCI-SIG.</span></td></tr></tbody></table><p>The 11 presets in PCIe 6.0 (Figure 3) are now annotated as Q0 through Q10, and their preshoots are proportionally higher compared to the PCIe 5.0 preshoots—in particular, presets 5 (Q4) through 9 (Q8).</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFCDs6znNzJ10nulp7dKR1uA3yZvLEGSjWAJ2G8E1k68F_TKu4qxbmICFyd2bniYiW4-1kLkkwKL6zmNIbIE0iKeRS2GdrmTDdAKZNCgph0GCEs8K7L8SKeX62Ba8aB3oj23bK4LUdZ8BCUIV55Wlgcj6MBEFpt46CPPXxj_mTVQFzMDpT0PNS9rLeTA/s775/SDA3_PCIE6_Presets.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="400" data-original-width="775" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFCDs6znNzJ10nulp7dKR1uA3yZvLEGSjWAJ2G8E1k68F_TKu4qxbmICFyd2bniYiW4-1kLkkwKL6zmNIbIE0iKeRS2GdrmTDdAKZNCgph0GCEs8K7L8SKeX62Ba8aB3oj23bK4LUdZ8BCUIV55Wlgcj6MBEFpt46CPPXxj_mTVQFzMDpT0PNS9rLeTA/w640-h330/SDA3_PCIE6_Presets.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. Tx Preset Ratios and Corresponding Coefficient Values for 64.0 GT/s from the PCI Express Base Specification Revision 6.0, 16 December 2021, Table 8-2 page on 1325. Courtesy of PCI-SIG.</span></td></tr></tbody></table><p>Figure 1 above shows an eye diagram of the Compliance Pattern using preset Q1 transmitter equalization coefficients, with the grid to the right of the eye diagram showing the pulse response for Q1 in magenta. The pulse response for Q0 without equalization, in yellow, is used as a reference to find Q1's best-fit transmitter equalization coefficients for C<span style="font-size: x-small;">-2</span>, C<span style="font-size: x-small;">-1</span>, C<span style="font-size: x-small;">0</span> and C<span style="font-size: x-small;">+1</span>. </p><h3 style="text-align: left;">Using SDAIII Software to Measure Transmitter Equalization</h3><p>The SDAIII software provides capabilities to measure Tx EQ and confirm that the preset values measured on the DUT conform to those in the specification.</p><p>The general process is to:</p><ul style="text-align: left;"><li>Configure the DUT to output the Compliance Pattern signal using preset Q0 with no equalization and acquire the Q0 differential signal.</li></ul><ul style="text-align: left;"><li>In the SDAIII software, display the pulse of the acquired signal and save it as a Reference waveform. You’ll now see two, “identical” waveforms on the display—one the Pulse in green and the other the saved PulseRef in yellow. </li></ul><p></p><p></p><ul style="text-align: left;"><li>Configure the DUT to output the Compliance Pattern using the next preset to be tested (e.g., Q1) and acquire the signal using the same settings as you did for the Q0 signal. Once the acquisition is processed, you should now see the signal with the new preset as the green Pulse waveform (see Figure 3). Measurements for that preset appear on the TxEQ table. </li></ul><p></p><ul style="text-align: left;"><li>Review the on screen table of TxEQ measurements and compare the values to Figure 2. Each should fall within the limits set forth in Table 8-2.</li></ul><p></p><p>For the full step-by-step instructions, download our application note, <i><a href="https://cdn.teledynelecroy.com/files/appnotes/pcie6.0tx-eq-measurements.pdf" target="_blank">Making PCIe 6.0 Transmitter Equalization Measurements with Your Oscilloscope</a></i>.</p><p>You must change the saved PulseRef waveform for measurements made on different days or using different equipment. In that case, click Delete Pulse Response Ref and repeat the entire procedure above.</p><h3 style="text-align: left;">Measuring Custom Presets</h3><p>The Tx EQ measurement tools can be used to test signals with custom presets following the same procedure as described above, saving the first acquisition with no equalization as the PulseRef. </p><h3 style="text-align: left;">Generating Step-Response Waveforms</h3><p>Optionally, you can view the Pulse and the PulseRef as step-response waveforms simply by selecting the checkboxes Show Step Response and Show Ref Step. The step-response waveforms are color-coded green and yellow the same as the pulse-response waveforms. </p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgig6nDsn5RcYkfPiksbnYVYxm9GXzvfb19rbLsOlmdjQ-sI_rcOTG7qOmzr1HZUQES3m-7uwJCo1DrKu-XaIR6frz2ehSlPtmx2b92RuWG1vfhCCUouenoZAbfFAVFLoKqRSa4dXDK10xZt26nCYITonknxYSJweF_Nz67l4NvCTUY-CqymVIgyDbjUg/s1932/SDA3_TxEQStep.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1083" data-original-width="1932" height="358" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgig6nDsn5RcYkfPiksbnYVYxm9GXzvfb19rbLsOlmdjQ-sI_rcOTG7qOmzr1HZUQES3m-7uwJCo1DrKu-XaIR6frz2ehSlPtmx2b92RuWG1vfhCCUouenoZAbfFAVFLoKqRSa4dXDK10xZt26nCYITonknxYSJweF_Nz67l4NvCTUY-CqymVIgyDbjUg/w640-h358/SDA3_TxEQStep.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 4. View the acquired signal as a step or pulse response waveform.</td></tr></tbody></table><br /><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2023/02/removing-oscilloscope-noise-from-pcie.html" target="_blank">Removing Oscilloscope Noise from PCIe 6.0 Compliance Pattern Measurements</a></div><div><a href="https://blog.teledynelecroy.com/2023/02/new-pcie-60-compliance-pattern.html" target="_blank">New PCIe 6.0 Compliance Pattern Measurements</a></div><div><a href="https://blog.teledynelecroy.com/2022/06/get-ready-for-pci-express-60-base.html" target="_blank">Get Ready for PCIe 6.0 Base Tx Testing--Compliance, Jitter and Eye Diagrams</a></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-48619882920982806452023-02-08T09:49:00.022-05:002023-03-16T11:18:34.876-04:00Removing Oscilloscope Noise from PCIe 6.0 Compliance Pattern Measurements<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmWh7vOiOOjgn2dDbDtFIaJgLTCr0di_7wA8yvikNJGr--qRKt5fxt96MxJeVuDGvc8eb08E-y464C1bJB10fmgaqTZnKqIIOzaLlzcqqPtAioGMZZs4p33SsDTB1tSKKRIYebX_iYwL7U9imZ0Y-OmyQMF-41sW82Wg5YSMNN5lLKU7lzJZJOii_fJA/s315/SDA3_Attenuator-finish.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="172" data-original-width="315" height="172" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmWh7vOiOOjgn2dDbDtFIaJgLTCr0di_7wA8yvikNJGr--qRKt5fxt96MxJeVuDGvc8eb08E-y464C1bJB10fmgaqTZnKqIIOzaLlzcqqPtAioGMZZs4p33SsDTB1tSKKRIYebX_iYwL7U9imZ0Y-OmyQMF-41sW82Wg5YSMNN5lLKU7lzJZJOii_fJA/s1600/SDA3_Attenuator-finish.png" width="315" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1. The new SDAIII-PCIE6 option offers<br />three methods for removing oscilloscope noise<br />from PCIe 6.0 Compliance Pattern measurements<br />as required by the standard.</td></tr></tbody></table>The new <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=691&groupid=103" target="_blank">SDAIII-PAMx</a> and <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=692&groupid=103" target="_blank">SDAIII-PCIE6</a> options for Teledyne LeCroy oscilloscopes enable you to quickly make new PCIe 6.0 noise measurements SNDR and RLM with the oscilloscope baseline noise removed, as required by the standard.<p></p><p>Here's a brief description of the three, proprietary noise removal methods from which you can choose.</p><h3 style="text-align: left;">Manual Method</h3><p>Manual uses the specified amount of oscilloscope noise for the <span style="font-size: large;">𝜎</span><span style="font-size: x-small;">scope</span> variable in the SNDRnr formula (described in the last post). This method is useful if you have previously measured your oscilloscope baseline noise and know what value to enter.<span></span></p><a name='more'></a><p></p><h3 style="text-align: left;">Baseline Method</h3><p>Baseline saves a reference of the input terminated into 50 𝝮, which is then compared to the unterminated input to determine the oscilloscope's intrinsic noise floor. The calculated oscilloscope noise is then computed into the SNDRnr measurement results. To use this method, you will save a Single acquisition of the unequalized Q0 signal, then connect the signal to a pair of 50 𝝮 terminators and measure again. </p><p></p><h3 style="text-align: left;">Attenuator Method</h3><p>The Attenuator method is the most accurate noise compensation method, since a signal is being applied
to the oscilloscope for both reference and measurement. It compares the SNR of a full-scale signal to the
SNR of an attenuated signal (at the same full-scale input range) to calculate the oscilloscope's noise
contribution to the SNDR as per the formula:</p><p><span style="font-size: large;">𝜎</span><span style="font-size: x-small;">FS</span><span style="font-size: large;">²</span> = <span style="font-size: large;">𝜎</span><span style="font-size: x-small;">scope</span><span style="font-size: large;">²</span> + <span style="font-size: large;">𝜎</span><span style="font-size: x-small;">signal</span><span style="font-size: large;">²<br /></span><span style="font-size: large;">𝜎</span><span style="font-size: x-small;">Att</span><span style="font-size: large;">²</span> = <span style="font-size: large;">𝜎</span><span style="font-size: x-small;">scope</span><span style="font-size: large;">²</span> + (<span style="font-size: large;">𝜎</span><span style="font-size: x-small;">signal</span><span style="font-size: large;">²</span> / K<span style="font-size: x-large;">²</span>)<br /><span style="font-size: large;">𝜎</span><span style="font-size: x-small;">scope</span><span style="font-size: large;">²</span> = (K<span style="font-size: large;"><span style="font-size: x-large;">²</span>𝜎</span><span style="font-size: x-small;">Att</span><span style="font-size: large;">²</span> – <span style="font-size: large;">𝜎</span><span style="font-size: x-small;">FS</span><span style="font-size: large;">²</span> / K<span style="font-size: x-large;">²</span>– 1)</p><p>where K is the attenuation value.</p><p>The <span style="font-size: large;">𝜎</span><span style="font-size: x-small;">scope</span> value is computed into the SNDRnr measurement results. </p><p>To use the Attenuator method, you will take a baseline measurement without attenuation, then connect a pair of 6 dB or 10 dB attenuators between the oscilloscope and DUT and measure again. </p><p></p><p>For the full step-by-step instructions, download our application note, <i><a href="https://cdn.teledynelecroy.com/files/appnotes/pcie6compliance-measurements.pdf" target="_blank">Making New PCIe 6.0 Compliance Pattern Measurements with Your Oscilloscope</a>.</i></p><p>Reference waveforms must be saved on the same day you make measurements, using the exact same equipment. When you change any part of your setup, or start a new test session, choose Delete Reference and repeat the procedure to save it before proceeding with measurements.</p><h4>Also see:</h4><div><a href="https://blog.teledynelecroy.com/2023/02/new-pcie-60-compliance-pattern.html" target="_blank">New PCIe 6.0 Compliance Pattern Measurements</a></div><div><br /></div><div><a href="https://blog.teledynelecroy.com/2022/06/get-ready-for-pci-express-60-base.html" target="_blank">Get Ready for PCIe 6.0 Base Tx Testing--Compliance, Jitter and Eye Diagrams</a></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-60250595741262478882023-02-06T08:00:00.013-05:002023-02-06T08:00:00.169-05:00New PCIe 6.0 Compliance Pattern Measurements <p>PCI Express® 6.0 features significant changes from PCIe® 5.0. In particular, PCIe 6.0 achieves its 64-GT/s data rate, double that of PCIe 5.0, by moving from non-return-to-zero (NRZ) signaling to four-level pulse-amplitude-modulation (PAM4) signaling. Consequently, PCIe 6.0 requires some new test methodologies and patterns, including a new PAM4 Compliance Pattern that finds use in multiple measurements.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCc7gMRjBTcP6kSQr_P0aT6QvHfRe6Y71Prl0uZ75VK844jBRaDWNv2pIHvlm-TvBWTt8a3OrfIiVsPVvDAddj5O36j_DDYW-ApFu6gpAhTj2pgvGlDrn60u4MUmtxVGO_5YslN1_UvAXKtQ0WdQrEkdIrHa9aLtDRN0-Tkmv1TZSI_YyGaUrOs0wHVg/s1184/PCIe6-CompliancePattern.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="309" data-original-width="1184" height="168" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCc7gMRjBTcP6kSQr_P0aT6QvHfRe6Y71Prl0uZ75VK844jBRaDWNv2pIHvlm-TvBWTt8a3OrfIiVsPVvDAddj5O36j_DDYW-ApFu6gpAhTj2pgvGlDrn60u4MUmtxVGO_5YslN1_UvAXKtQ0WdQrEkdIrHa9aLtDRN0-Tkmv1TZSI_YyGaUrOs0wHVg/w640-h168/PCIe6-CompliancePattern.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1. The new PCIe 6.0 Compliance Pattern signal. Click any image to enlarge.</td></tr></tbody></table><p>The new Compliance Pattern is used for calculating signal to noise and distortion ratio (SNDR), as well as ps21TX (the package insertion loss) and the transmitter ratio of level mismatch (RLM). In addition, it is used to measure transmitter equalization coefficients.</p><p style="text-align: left;"><span></span></p><a name='more'></a><p></p><h3 style="text-align: left;">What's in the Compliance Pattern Signal</h3><p>The new Compliance Pattern signal (shown in Figure 1 above) contains low-frequency patterns, such as strings of 64 0s, 1s, 2s and 3s, enabling a long run of each of the voltage levels found in PAM4. It also contains a big section of pseudorandom binary sequence (PRBS) data using PAM4. </p><p></p><ul style="text-align: left;"><li>Section 1 contains a long run of 2s and 1s. </li><li>Section 2 is the big section containing PRBS data. </li><li>Section 3 contains a long run of 3s and 0s followed by a clock pattern.</li><li>Section 4 contains another long run of 3s and 0s. </li></ul><p></p><p>More PRBS data follows section 4, and the Compliance Pattern signal repeats itself. One or more of these sections in the Compliance Pattern signal can assist in the calculation of SNDR and other parameters.</p><h3 style="text-align: left;">SNDR Measurement</h3><p></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtuycKnOtON9hkpcxYDNRL3iGWfIu1hV0ptAbmExjqSoWk0BTrr2LKjZYwNOmB24kt416HSNmq0bUDQ-2yTW-uIx4yf8MohD3fbRDGykbb2ag9-mZe0mEZ93h7dCnRpTwV_LNHmPANboAQzo9z5kc72c9c2EDQp7XFzQmvt7VFfIfyZW4TfDGkxZiA7Q/s868/SDA_SNDR_eq.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="159" data-original-width="868" height="74" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtuycKnOtON9hkpcxYDNRL3iGWfIu1hV0ptAbmExjqSoWk0BTrr2LKjZYwNOmB24kt416HSNmq0bUDQ-2yTW-uIx4yf8MohD3fbRDGykbb2ag9-mZe0mEZ93h7dCnRpTwV_LNHmPANboAQzo9z5kc72c9c2EDQp7XFzQmvt7VFfIfyZW4TfDGkxZiA7Q/w400-h74/SDA_SNDR_eq.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. SNDR equation variables.</span></td></tr></tbody></table><p>SNDR refers to the Signal to Noise and Distortion Ratio. Figure 2 shows the breakdown of the SDNR equation in terms of the variables P<span style="font-size: x-small;">max</span> (the signal strength), <span style="font-size: medium;">𝜎</span><span style="font-size: x-small;">n</span> (noise) and <span style="font-size: medium;">𝜎</span><span style="font-size: x-small;">e</span> (distortion).</p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpEYh2xyhrt3Bc73iPNWv_gAhPDndDzcGlcMDdktJrd9fcB050fQqXl3-qulvLRipsLslADbsHhcQ2kyMydoeMQXy_0Zyvtj7MrutZBjaHCtm4mhFvoTF9oxXm-QRDMRcszYcHzRdL7rcpxdDMs2kS1WQFpDQULp1gVR133Ogb9NbXi54ihUWxbY9K3g/s1478/PCIe6-Pmax.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="803" data-original-width="1478" height="174" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpEYh2xyhrt3Bc73iPNWv_gAhPDndDzcGlcMDdktJrd9fcB050fQqXl3-qulvLRipsLslADbsHhcQ2kyMydoeMQXy_0Zyvtj7MrutZBjaHCtm4mhFvoTF9oxXm-QRDMRcszYcHzRdL7rcpxdDMs2kS1WQFpDQULp1gVR133Ogb9NbXi54ihUWxbY9K3g/s320/PCIe6-Pmax.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. P</span><span style="font-size: x-small; text-align: left;">max</span><span style="text-align: left;"> measurement.</span></td></tr></tbody></table>The P<span style="font-size: x-small;">max</span> component of SNDR is calculated by using a pulse response, which is an extracted linear model of the transmitter signal. The pulse response is measured at the transmitter to describe the behavior of the transmitter as a filter if you apply the filter to a 1-UI pulse. P<span style="font-size: x-small;">max</span> is the maximum amplitude of the extracted pulse response (Figure 3), and it can be affected by various factors such as the channel bandwidth.<p></p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiigZF3ryEvDcHYcA5JjJpd4XvBfzHUBhbUnE8JApr-Q0CgThzie79ewpRou1TaS7k7c1vPTXzbIf8G_5HtqD5J1QAlVmOikIdHjoqNE-RwpcKlyXjYRxNKLqu9g1tmbNhh_iVxBmM44CjyGd0Lof1XRCAhk_ed60ZQ67yM7vTH0qQDMPuwa1qleCiwIg/s1478/PCIe6-Noise.PNG" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="810" data-original-width="1478" height="175" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiigZF3ryEvDcHYcA5JjJpd4XvBfzHUBhbUnE8JApr-Q0CgThzie79ewpRou1TaS7k7c1vPTXzbIf8G_5HtqD5J1QAlVmOikIdHjoqNE-RwpcKlyXjYRxNKLqu9g1tmbNhh_iVxBmM44CjyGd0Lof1XRCAhk_ed60ZQ67yM7vTH0qQDMPuwa1qleCiwIg/s320/PCIe6-Noise.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. Noise variable </span><span style="font-size: medium; text-align: left;">𝜎</span><span style="font-size: x-small; text-align: left;">n</span><span style="text-align: left;"> measurement.</span></td></tr></tbody></table><br />The noise component of the signal, notated <span style="font-size: medium;">𝜎</span><span style="font-size: x-small;">n</span>, is measured on the 61st UI of the 64-UI-long runs of 0s, 1s, 2s and 3s in the Compliance Pattern signal (Figure 4). The 61st UI is chosen for this measurement because, in theory, the signal has had plenty of time to settle down to its equilibrium state by the time the 61st UI arrives.<p><br /></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjT9YotLGVo-0aQlz-W4T4X9Mic50EhWbqtoAiPlsuLU0Ork9qnwbr0dXkAsuXW59G9gZOObzNar2vHH135QmsNNSwdB__IG7kA2X7H_vQoUpjgefjmRx4PT1Ltz5mYKUqdbcLUb2gyVQ_i5t7CbGW4pCbM2pBZmfSY-7hHq-Q_RX22GQt0qJPxxi3gdQ/s1480/PCIe6-Distortion.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="797" data-original-width="1480" height="172" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjT9YotLGVo-0aQlz-W4T4X9Mic50EhWbqtoAiPlsuLU0Ork9qnwbr0dXkAsuXW59G9gZOObzNar2vHH135QmsNNSwdB__IG7kA2X7H_vQoUpjgefjmRx4PT1Ltz5mYKUqdbcLUb2gyVQ_i5t7CbGW4pCbM2pBZmfSY-7hHq-Q_RX22GQt0qJPxxi3gdQ/s320/PCIe6-Distortion.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 5. Distortion variable </span><span style="font-size: medium; text-align: left;">𝜎</span><span style="font-size: x-small; text-align: left;">e</span><span style="text-align: left;"> measurement.</span></td></tr></tbody></table><p>The last component of the SNDR equation is <span style="font-size: medium;">𝜎</span><span style="font-size: x-small;">e</span>, which is the distortion variable. It is a measure of how much the average signal deviates from the extracted pulse-response shape and is measured on the PRBS section of the compliance-pattern signal. In Figure 5, you can see three traces in the top grid. The red trace is the ideal pattern; the blue trace, which is overlapping the red trace, represents the average of the captured pattern; and the green trace is the difference between the average and ideal patterns, which is equal to the distortion <span style="font-size: medium;">𝜎</span><span style="font-size: x-small;">e</span>.</p><p>Combining all three components returns the SNDR measurement, but the basic SNDR equation of Figure 2 is missing an important variable—the oscilloscope noise (<span style="font-size: medium;">𝜎</span><span style="font-size: x-small;">scope</span>). The oscilloscope noise impacts the SNDR of a real-life device, and it must be considered if you want to have an accurate SNDR measurement for your device. Figure 6 shows the equation for SNDR with the oscilloscope noise removed (SNDR<span style="font-size: xx-small;">NR</span>). </p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjom3kNBVplqWrglHYheNWbsk1VnQoRi2ZGzWB-O-EWsaA4FFXG5peUWgbM_KoWEmOwE4Nswm5wNdsQitnyud_c73j3HcNRe_J91SYh33B0eyBWFX7llXyFuNLIcpTvg0lGZKDMY27KlfTPewW4Q-yYa0kO3p645j9XOUVLrQqTiI1lpXmCj1aVZZGxoQ/s696/SDA_SNDRscope_eq.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="138" data-original-width="696" height="63" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjom3kNBVplqWrglHYheNWbsk1VnQoRi2ZGzWB-O-EWsaA4FFXG5peUWgbM_KoWEmOwE4Nswm5wNdsQitnyud_c73j3HcNRe_J91SYh33B0eyBWFX7llXyFuNLIcpTvg0lGZKDMY27KlfTPewW4Q-yYa0kO3p645j9XOUVLrQqTiI1lpXmCj1aVZZGxoQ/w320-h63/SDA_SNDRscope_eq.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 6. SNDR</span><span style="font-size: x-small; text-align: left;">NR</span><span style="text-align: left;"> equation with oscilloscope noise removed.</span></td></tr></tbody></table><p>Teledyne LeCroy's PCIe 6.0 Base Transmitter compliance test solution implements several noise-removal methodologies. The bottom of Figure 6 shows two measurements that were made on a Teledyne LeCroy LabMaster oscilloscope. The first is the SNDR without oscilloscope noise removed, and the second is the SNDRNR measurement with the oscilloscope noise removed. </p><h3 style="text-align: left;">RLM Measurement</h3><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgk01j72H-VQbXyWBgT0RT1bi1UuD5MmUNHcXjZaBgc2bn76fUicxt0QJPhANn0W76lp7ZmHF6N12n9CLMRHRsWclo_6E6K4GENWYraafIIAeL1FgmRW6dSABDd5MMZAjN8Y8DCgWlFgyPJdWAu7vv47wuZhS_F6oGkKTigc9V5mtcER6P3cFGMXfKBZA/s1934/SDA_PAM4_RLM_measure.PNG" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="843" data-original-width="1934" height="139" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgk01j72H-VQbXyWBgT0RT1bi1UuD5MmUNHcXjZaBgc2bn76fUicxt0QJPhANn0W76lp7ZmHF6N12n9CLMRHRsWclo_6E6K4GENWYraafIIAeL1FgmRW6dSABDd5MMZAjN8Y8DCgWlFgyPJdWAu7vv47wuZhS_F6oGkKTigc9V5mtcER6P3cFGMXfKBZA/s320/SDA_PAM4_RLM_measure.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 7. V</span><span style="font-size: x-small; text-align: left;">0</span><span style="text-align: left;">, V</span><span style="font-size: x-small; text-align: left;">1</span><span style="text-align: left;">, V</span><span style="font-size: x-small; text-align: left;">2</span><span style="text-align: left;"> </span><span style="text-align: left;">and V</span><span style="font-size: x-small; text-align: left;">3 </span><span style="text-align: left;">signal levels <br />for calculating the transmitter RLM.</span></td></tr></tbody></table>Transmitter linearity is defined as a function of the mean signal levels V<span style="font-size: x-small;">0</span>, V<span style="font-size: x-small;">1</span>, V<span style="font-size: x-small;">2</span> and V<span style="font-size: x-small;">3</span> transmitted for PAM4 two-bit symbols, as shown in Figure 7. <p></p><p>Transmitter RLM is defined by the following equations involving V<span style="font-size: x-small;">0</span>, V<span style="font-size: x-small;">1</span>, V<span style="font-size: x-small;">2</span> and V<span style="font-size: x-small;">3</span>:</p><p> V<span style="font-size: x-small;">mid</span> = (V<span style="font-size: x-small;">0</span> + V<span style="font-size: x-small;">3</span>) / 2</p><p> ES<span style="font-size: x-small;">1</span> = (V<span style="font-size: x-small;">1 </span>– V<span style="font-size: x-small;">mid</span>) / (V<span style="font-size: x-small;">0</span> – V<span style="font-size: x-small;">mid</span>)</p><p> ES<span style="font-size: x-small;">2</span> = (V<span style="font-size: x-small;">2</span> – V<span style="font-size: x-small;">mid</span>) / (V<span style="font-size: x-small;">3 </span>– V<span style="font-size: x-small;">mid</span>)</p><p> RLM = min((3 x ES<span style="font-size: x-small;">1</span> ), (3 x ES<span style="font-size: x-small;">2</span> ), (2 – (3 x ES<span style="font-size: x-small;">1</span> )), (2 – (3 x ES<span style="font-size: x-small;">2</span> )))</p><p>RLM is measured using the same section of the Compliance Pattern signal used for <span style="font-size: medium;">𝜎</span><span style="font-size: x-small;">n</span> for the SNDR measurement, which is the 64-UI-long runs of 0s, 1s, 2s and 3s. The RLM measurement is straightforward. The goal is to have evenly spaced transition levels and to have RLM equal to 1.</p><h3 style="text-align: left;">ps21<span style="font-size: x-small;">TX</span> Measurement</h3><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8hd8NmdD9uqoYnkUG-Ehu1F1lQdiqzTf6OTE2vNlBKvofBLXPZ73E5v86UkW19qq3f8QWuNvmcEC4e5pBCDwK9Juf1gbC3ShLnqDcfB0HSjKBPCTDcnQD5U_GhNUElEOcesAxRxXVdcuHnAekL9-6zF8khXR03FSab1bDsNdN-guvxDPaC1Blxi2tTA/s1479/PCIe6-ps21.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="836" data-original-width="1479" height="181" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8hd8NmdD9uqoYnkUG-Ehu1F1lQdiqzTf6OTE2vNlBKvofBLXPZ73E5v86UkW19qq3f8QWuNvmcEC4e5pBCDwK9Juf1gbC3ShLnqDcfB0HSjKBPCTDcnQD5U_GhNUElEOcesAxRxXVdcuHnAekL9-6zF8khXR03FSab1bDsNdN-guvxDPaC1Blxi2tTA/s320/PCIe6-ps21.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 8. ps21<span style="font-size: xx-small;">TX</span> measurement.</td></tr></tbody></table>A key voltage measurement to make for PCIe 6.0 Base transmitter testing is the ps21<span style="font-size: xx-small;">TX</span> measurement—the effective transmitter package loss. This measurement was also defined in the PCIe 5.0 Base specifications, so it's not a new measurement for PCIe 6.0. The package loss is measured by comparing the 64 0s and 64 1s voltage swing against a 1, 0, 1, 0 clock pattern. The ps21<span style="font-size: xx-small;">TX </span>measurement is conducted with no transmitter equalization, and it is made by averaging over 500 repetitions of the Compliance Pattern signal to reduce noise. The measurement is illustrated in Figure 8, where V111 is the amplitude of a low-frequency signal and V101 is the amplitude of a high-frequency signal. The ps21<span style="font-size: xx-small;">TX </span>measurement is then defined as follows: <p></p><p style="text-align: center;">ps21<span style="font-size: xx-small;">TX </span>= 20 × <i>log</i><span style="font-size: x-small;">10</span> (V<span style="font-size: x-small;">101</span> / V<span style="font-size: x-small;">111</span> )</p><p>Adding the <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=691&groupid=103" target="_blank">SDAIII-PAMx</a> and <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=692&groupid=103" target="_blank">SDAIII-PCIE6</a> options to Teledyne LeCroy oscilloscopes provides all the software tools needed to easily make the new Compliance Pattern measurements to the PCIe standard, including the required oscilloscope noise removal. We'll discuss the noise removal methods in our next post. </p><p>Download our application note, <i><a href="https://cdn.teledynelecroy.com/files/appnotes/pcie6compliance-measurements.pdf" target="_blank">Making New PCIe 6.0 Compliance Pattern Measurements with Your Oscilloscope</a>.</i></p><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2022/06/get-ready-for-pci-express-60-base.html" target="_blank">Get Ready for PCIe 6.0 Base Tx Testing--Compliance, Jitter and Eye Diagrams</a></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-56982757707766640042023-01-25T16:39:00.002-05:002023-02-09T08:22:51.379-05:00Eliminating DC Resistively Coupled Noise: A Signal and Power Integrity Tutorial<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiqqC6rD97OUalr5VQKYxPwE8tmXxobHY-7hrMcAJO9T1lVMzk8LWHkLS35cJeBnrUNI6VOhfJrI9jpxZAk3YDm8Y5LqilngCXA3nsmWD-SK-XVUERKeD1HduNbuyqOmAYH3vZIQ9K1kWfBM-WOjx9EAkQ0Re3h5CW7RMxdTWvOYVANw5E7hQamXma-wA/s1305/SplitGround_Fig8.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="492" data-original-width="1305" height="151" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiqqC6rD97OUalr5VQKYxPwE8tmXxobHY-7hrMcAJO9T1lVMzk8LWHkLS35cJeBnrUNI6VOhfJrI9jpxZAk3YDm8Y5LqilngCXA3nsmWD-SK-XVUERKeD1HduNbuyqOmAYH3vZIQ9K1kWfBM-WOjx9EAkQ0Re3h5CW7RMxdTWvOYVANw5E7hQamXma-wA/w400-h151/SplitGround_Fig8.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 8. The measured voltage noise on the victim <br />trace, on the other side of the ground plane gap, <br />showing no resistively coupled cross talk on the <br />order of 10 uV, the noise floor of the measurement.</span></td></tr></tbody></table><p></p><p>The following is excerpted from Professor Eric Bogatin's article in the Signal Integrity Journal, <a href="https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.signalintegrityjournal.com%2Farticles%2F2982-the-case-for-split-ground-planes&data=05%7C01%7Cwtyler%40horizonhouse.com%7C5ed90a35003747eb05e508db09e31fe2%7C85f2fc98a3c44064815d1efc67da1928%7C0%7C0%7C638114643337382115%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=j%2BfqAZUuEKOAzlr5Vd5bkNCXxXh03S%2FQNQ1vOSN9YuM%3D&reserved=0"><i>The Case for Split Ground Planes</i></a><i><span face="Calibri, sans-serif"><span style="font-size: 14.6667px;">.</span></span></i> Reprinted by permission of Signal Integrity Journal.</p><p>This section continues from the discussion on <a href="https://blog.teledynelecroy.com/2023/01/inductively-coupled-noise-and.html" target="_blank">Inductively Coupled Noise and Resistively Coupled Noise</a>.</p><p>. . .</p><p>When we cut a gap in the return plane, there will be no DC current flow across the gap. There will be magnetic field coupling across the gap which is why we still see significant mutual inductance coupling between the aggressor and victim across the gap. The gap has only a small impact on this noise.</p><p>However, we would expect there would be no resistively coupled noise on the victim trace on the other side of the ground plane gap. In Figure 8, the resistively coupled noise is measured with the same scale and averaging as the noise on the victim line with no gap. The noise floor of this measurement is about 10 uV. To this level, there is no measurable resistively coupled noise, a significant reduction. <span></span></p><a name='more'></a><p></p><p>There is still inductively coupled switching noise which lasts for the rise time of the square wave, about 9 nsec. This noise is just barely visible with this time base of 100 usec/div. It is the initial spike at the edges of the square wave. </p><p>It is this small amount of resistively coupled cross talk which a gap in the ground plane would prevent. It keeps the DC currents, which will spread out from the signal paths, from flowing in the ground plane to induce a DC offset noise in the return path of other signals. </p><p>Generally, this amount of noise will be on the order of 100 uV, corresponding to 100 mA flowing through 1 mohm of coupled resistance. In an ADC with a 5 V reference and 15 bit resolution (plus sign), 1 bit would be a voltage level of about 5 V/32,000 = 150 uV. The DC coupled ground plane voltage noise could contribute about 1 least significant bit (LSB) level. Fluctuations in the 100 mA of ground currents, could be just at the sensitivity level of a 16 bit ADC in some cases. It would be noticeable in a 24-bit ADC.</p><p>One solution to reduce this noise would be to isolate either the high current paths or the sensitive signal paths using an isolating gap in the return plane, parallel with the signal conductors, making sure no signals crossed this isolating gap. This is the problem solved by a gap in the return plane. </p><p>If there are 100 A of DC current flowing, this ground plane noise could be 100 mV or more, but then other design considerations such as thicker copper, more ground planes and placement of the VRM in proximity to the load might be employed. </p><p>While a gap in the return plane would dramatically reduce the resistively coupled noise on analog signals where voltage noise on the order of 100 uV was important, there is a more effective way of reducing this sort of common noise on sensitive signals that is also robust and does not run the risk of inadvertently having signals cross the isolation gap. </p><h3 style="text-align: left;">Differential Signaling also Eliminates the Resistive Coupled DC Cross Talk</h3><p>Most applications which are sensitive to 100 uV of low frequency noise involve measuring low level signals from sensors or microphones. An important design guideline when measuring these sorts of voltage sources is to use a differential measurement. </p><p>If the sensor itself generates a differential signal or even a single ended signal, you would route a separate trace for both the high and low ends of the sensor, back to a differential receiver, such as an instrumentation amplifier. Even if the sensor is single ended, the ground connection to the sensor’s low side could be connected at only one point, either at the sensor or at the input to the differential receiver, rather at both ends. </p><p>The voltage difference between the high and low side of the sensor is brought back to the input of the differential receiver, without using the ground plane, which might have the common DC voltage drop coupled noise in it. This separate dedicated low trace would not have the DC current of the return plane traveling in it.</p><p>This principle is illustrated in a simple experiment. A TMP36, a voltage sensitive temperature sensor, was used as the sensor. At room temperature, it generates a DC voltage of about 730 mV. It is a single ended signal. </p><p>The output of this sensor was measured with a differential amplifier and a 16-bit ADC using the ADS1115. It was measured in two configurations, with the low side connected to the ADC using a common ground path and with a separate return line connecting the low side of the sensor to the low side input of the ADC. </p><p>While these measurements were being made, a 1 Hz square wave of current was passed through the common return path. The common resistance was increased to accentuate the coupled noise. When the 100 mA of ground current was sent through the ground path, a noise level of about 2 mV was generated in the ground path from the sensor to the ADC. This voltage noise appears in series with the low-level sensor voltage when the return path is used to connect the low side reference. </p><p>When the low side reference is carried in a separate, isolated trace, there is no impact on the differential signal from the DC noise in the return path. This result is shown in Figure 9.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpxj_QlPgiQeUyBr73w6gbGYLDB9nBYP-mn45E52FX_exGrnULbEAnE9tf8a52M00AJNnY4wBVH-eZz8TkYKDrIpxr-Y25VO3cFUKOAmysqwRiQS35SDwJICHo3K5y4UZFwDPDdJ1eGhudMENknyVXvJW8vuwsO95gkEg4qZS0BXwQWMiZCtjwsgwnIQ/s1455/SplitGround_Fig9.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="416" data-original-width="1455" height="182" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpxj_QlPgiQeUyBr73w6gbGYLDB9nBYP-mn45E52FX_exGrnULbEAnE9tf8a52M00AJNnY4wBVH-eZz8TkYKDrIpxr-Y25VO3cFUKOAmysqwRiQS35SDwJICHo3K5y4UZFwDPDdJ1eGhudMENknyVXvJW8vuwsO95gkEg4qZS0BXwQWMiZCtjwsgwnIQ/w640-h182/SplitGround_Fig9.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 9. The circuit set up for the measured analog voltage using the ground as the low side reference or a separate trace to the differential input. The measurements on the right show the ground noise on the signal ended signal, but no impact on the differential measurement.</span></td></tr></tbody></table><p>The differential signal path from the sensor to the differential receiver, does not have the voltage drop of the ground plane in its path. The measured signal does not show any of the DC resistive cross talk in its signal. This is the way to route sensitive analog signals so they are not sensitive to very slight resistive cross talk from low level signals. </p><h3 style="text-align: left;">Conclusion</h3><p>The problem a split in the ground plane solves is reducing the very small low frequency resistive cross talk of return currents which spread out. This typically arises at frequencies below 10 kHz and is equivalent of a common, shared resistance on the order of a few squares of sheet resistance, on the order of 1 mohm. </p><p>If your application has very low-level analog signals which must be routed across a board and might be sensitive to these low-level sources of low-frequency noise, a better solution is to use differential signal routing and a differential receiver. </p><p>The risk of adding a split in the ground plane to fix this very small problem is the possibility of higher bandwidth signals inadvertently crossing this gap. This can result in a pathological problem which will easily cause a board to fail in a number of ways. </p><p>Except in the simplest of boards, the risk from including a gap in the return path, strongly outweighs the potential benefit. Carefully consider your engineering rationale to add a split in the ground plane and to reduce risk, consider alternative solutions.</p><p>. . .</p><div><h4>Also see:</h4><div><a href="https://blog.teledynelecroy.com/2023/01/inductively-coupled-noise-and.html" target="_blank">Inductively Coupled Noise and Resistively Coupled Noise</a></div><div><a href="https://blog.teledynelecroy.com/2023/01/return-current-at-low-frequency-signal.html" target="_blank">Return Current at Low Frequency</a></div><div><a href="https://blog.teledynelecroy.com/2023/01/signal-return-paths-signal-and-power.html" target="_blank">Signal Return Paths</a></div></div><div><div><a href="https://blog.teledynelecroy.com/2022/01/transmission-lines-for-oscilloscope.html" target="_blank">Transmission Lines for Oscilloscope Users, Part 1</a></div><div><a href="https://blog.teledynelecroy.com/2014/08/go-back-to-school-on-signal-integrity.html" target="_blank">Go Back to School on Signal Integrity</a></div></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-18153119664872026212023-01-23T08:00:00.289-05:002023-02-09T08:22:23.243-05:00Inductively Coupled Noise and Resistively Coupled Noise: A Signal and Power Integrity Tutorial<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipFCXq7x0JYimM9U2hIw26h0mj8Q_KRL4M_yEt6Ca62jRRBUhO49uOLvb2yuafbK0bITzkISxz8eGlBweRLfgp1SguNI8y5HWWgBicPoCVhmQQ1N_uLfjN3Apr9fu_NC92nmNJPuXMNgXzHnuzOTdMjtzlw2LT2nvJs3dv0kDnXKS8A5VmwkvlRBMA-Q/s1357/SplitGround_Fig6.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="758" data-original-width="1357" height="179" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipFCXq7x0JYimM9U2hIw26h0mj8Q_KRL4M_yEt6Ca62jRRBUhO49uOLvb2yuafbK0bITzkISxz8eGlBweRLfgp1SguNI8y5HWWgBicPoCVhmQQ1N_uLfjN3Apr9fu_NC92nmNJPuXMNgXzHnuzOTdMjtzlw2LT2nvJs3dv0kDnXKS8A5VmwkvlRBMA-Q/s320/SplitGround_Fig6.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 6. Measuring the inductively coupled noise <br />on the victim trace adjacent to the aggressor <br />signal with no gap and separated by a gap. <br />The inductively coupled noise is reduced by <br />about 40% on the victim trace separated by a gap. <br />This is a small impact.</span></td></tr></tbody></table><p></p><p>The following is excerpted from Professor Eric Bogatin's article in the Signal Integrity Journal, <a href="https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.signalintegrityjournal.com%2Farticles%2F2982-the-case-for-split-ground-planes&data=05%7C01%7Cwtyler%40horizonhouse.com%7C5ed90a35003747eb05e508db09e31fe2%7C85f2fc98a3c44064815d1efc67da1928%7C0%7C0%7C638114643337382115%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=j%2BfqAZUuEKOAzlr5Vd5bkNCXxXh03S%2FQNQ1vOSN9YuM%3D&reserved=0"><i>The Case for Split Ground Planes</i></a><i><span face="Calibri, sans-serif"><span style="font-size: 14.6667px;">.</span></span></i> Reprinted by permission of Signal Integrity Journal.</p><p>This section continues from the discussion on <a href="https://blog.teledynelecroy.com/2023/01/return-current-at-low-frequency-signal.html" target="_blank">Return Current at Low Frequency</a>.</p><p>. . .</p><h3 style="text-align: left;">Inductively Coupled Noise</h3><p>In a plane, at frequencies below about 10 kHz, return currents will not flow under the signal path, but will spread out in the return plane. Above 10 kHz, the return currents are localized under the signal paths. </p><p>When we have two adjacent signal paths that are over a wide, continuous plane, they will show inductive cross talk at high frequency. Even with minimal overlap of the return currents, there is still loop mutual inductance between the two signal-return paths. This inductive noise is driven by the changing current, the dI/dt, in the aggressor signal-return path, which will get smaller at lower frequency.<span></span></p><a name='more'></a><p></p><p>An aggressor signal with a transient, short rise time current edge, will result in a noise signature on an adjacent victim line with a derivative of the aggressor current. The inductive noise would only appear synchronous with the switching current edge. This is why we call this sort of inductively generated noise “switching noise” since it only occurs when signals switch transition levels. As the current change drops off, with a lower slope, the inductive cross talk drops off until it is below a measurement threshold. </p><p>This behavior was demonstrated in a simple board. In a two-layer board, we constructed six parallel, identical microstrip traces. One was the aggressor. Its far end was shorted to ground. A 2 kHz square wave of 120 mA peak to peak current was transmitted down the aggressor. The rise time was about 9 nsec, but the current was at a constant value for the rest of the period.</p><p>There were two victim traces symmetrically on either side of the aggressor. Between the aggressor and one of the victim lines, a gap in the return plane was cut. This isolated the return currents from the aggressor. They were unconstrained to one victim line, be eliminated from flowing under the other victim trace. </p><p>We expect to see switching noise on the adjacent victim trace that lasts only during the 9 nsec of the rise time. The rest of the period should show no switching noise. The measured switching noise on the two victim traces shows the impact from the gap in the return plane. Figure 6 shows the measurement set up of the two configurations and the measured inductively coupled cross talk on the two victim traces. </p><p>We see the signature of the switching noise as the derivative of the current edge. From the measured peak crosstalk, on the order of 5 mV in this example, the rise time, and the current peak, we can estimate the loop mutual inductance between the aggressor and the victim. With no gap, this is about 0.4 nH of loop mutual inductance. On the other side of the gap, it is reduced to about 0.25 nH. The gap redistributed the return currents and did reduce the loop mutual inductance to the victim trace on the other side of the gap. But it was by a small amount. </p><h3 style="text-align: left;">Low Frequency Resistive Coupled Cross Talk</h3><p>At low frequency, when the return currents spread out, they will create a voltage drop distribution in the return plane due to the resistance in the plane. With a typical resistance in the return path on the order of 1 mohm, and currents on the order of 100 mA, this is a voltage drop between one region of the return plane and another on the order of 100 uohms, for example. This voltage drop due to the low frequency, DC currents on the plane, would appear as a voltage difference between the signal and local return plane on the victim path. It would show up at low frequency and last into DC. However, the magnitude of the resistively coupled noise might be orders of magnitude lower than the inductively coupled noise. </p><p>If there were a parallel gap in the return plane between the aggressor and victim traces, the impact on the inductive cross talk would be small. However, the parallel gap would prevent DC currents from the aggressor’s return current from flowing under the victim trace and would eliminate the already small resistively coupled cross talk. </p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj2DmvumZuLlaVrBe6I8lzjTD064kg9sybul66U1TGtqWTZ-bdHYgP4kT6AFZYZKvX9j2nEd2FaomwQ7jjN2KDGPku2daBntJsWrCPGd6_gVmRnehG7fbZGEbgEQmZPW23W1lfTkgW-M3HQgNMUvEDTPBwMEWwTnDUlYOfh9OpWYBWUJvOWmBL7P6IqHA/s631/SplitGround_Fig7.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="631" data-original-width="550" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj2DmvumZuLlaVrBe6I8lzjTD064kg9sybul66U1TGtqWTZ-bdHYgP4kT6AFZYZKvX9j2nEd2FaomwQ7jjN2KDGPku2daBntJsWrCPGd6_gVmRnehG7fbZGEbgEQmZPW23W1lfTkgW-M3HQgNMUvEDTPBwMEWwTnDUlYOfh9OpWYBWUJvOWmBL7P6IqHA/s320/SplitGround_Fig7.png" width="279" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 7. The measured voltage noise on the <br />victim trace with a scale of 20 uV/div. The<br />raw measurement in one acquisition shows <br />the oscilloscope amplifier noise which is <br />reduced with 250 acquisitions averaged <br />together. Note the switching noise which <br />occurs at the edges of the square wave <br />is just visible on this time base scale.</span></td></tr></tbody></table>The resistive cross talk can be measured during the part of the square wave when the current is constant. Figure 7 shows the same measurement of the voltage on the victim trace with no gap between it and the aggressor signal, during the entire square wave of current, but on a much higher resolution voltage scale. <p></p><p>This is a very difficult measurement because the resistively coupled cross talk is so small. With no averaging, the cross talk is smaller than the 100 uV rms amplifier noise of the Teledyne LeCroy WavePro HD, 12-bit scope. To reduce the random noise, we have to average consecutive acquisitions, triggering the scope with the function generator’s square wave. The random noise decreases with the square root of the number of averages, but the cross talk synchronous with the function generator, stays the same. </p><p>We see the very clear DC signature of the resistively coupled noise on the victim trace. Its magnitude is about 120 uV peak to peak. The small offset of about 20 uV is the DC offset of the scope’ amplifier. This 120 uV of resistively coupled noise for a peak-to-peak current of 120 mA corresponds to a coupled resistance in the ground plane of about 120 uV/120 mA = 1 mohm of resistance, or the resistance in about 2 squares of ground plane for this board.</p><p>This 120 uV of resistive noise is due to the overlap of the return currents of the two conductors, roughly 1 inch apart, with 120 mA of aggressor current, passing through the 1 mohm of overlapping plane resistance. This is the cross-talk noise which we would want to eliminate with a split ground plane. </p><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2023/01/return-current-at-low-frequency-signal.html" target="_blank">Return Current at Low Frequency</a></div><div><a href="https://blog.teledynelecroy.com/2023/01/signal-return-paths-signal-and-power.html" target="_blank">Signal Return Paths</a></div><div><div><a href="https://blog.teledynelecroy.com/2022/01/transmission-lines-for-oscilloscope.html" target="_blank">Transmission Lines for Oscilloscope Users, Part 1</a></div><div><a href="https://blog.teledynelecroy.com/2014/08/go-back-to-school-on-signal-integrity.html" target="_blank">Go Back to School on Signal Integrity</a></div></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-3404871130558302342023-01-18T08:00:00.003-05:002023-02-09T08:22:03.364-05:00Return Current at Low Frequency: A Signal and Power Integrity Tutorial<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkUgvKE7oBUBdbAD8VHIsDymQcFz3fOClgN5zUAv371N8iNVzJ1_BZ2UOp5qu2k2v5r4GewgmjnTL0hnoyV3Be1IKbfB2IEkOo0ixtzxBo9jhkFB1AYA5ZTEmBLe3AFANTAonaP0_pskNsAoIWzT4NUk-bpPXNiQGzcpr2ZfL8WIbbDjH9MKsYdwsVUg/s668/SplitGround_Fig3.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="622" data-original-width="668" height="298" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkUgvKE7oBUBdbAD8VHIsDymQcFz3fOClgN5zUAv371N8iNVzJ1_BZ2UOp5qu2k2v5r4GewgmjnTL0hnoyV3Be1IKbfB2IEkOo0ixtzxBo9jhkFB1AYA5ZTEmBLe3AFANTAonaP0_pskNsAoIWzT4NUk-bpPXNiQGzcpr2ZfL8WIbbDjH9MKsYdwsVUg/s320/SplitGround_Fig3.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. Specially configured coax cable with <br />the front and back of the shield shorted together.</span></td></tr></tbody></table><p></p><p>The following is excerpted from Professor Eric Bogatin's article in the Signal Integrity Journal, <a href="https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.signalintegrityjournal.com%2Farticles%2F2982-the-case-for-split-ground-planes&data=05%7C01%7Cwtyler%40horizonhouse.com%7C5ed90a35003747eb05e508db09e31fe2%7C85f2fc98a3c44064815d1efc67da1928%7C0%7C0%7C638114643337382115%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=j%2BfqAZUuEKOAzlr5Vd5bkNCXxXh03S%2FQNQ1vOSN9YuM%3D&reserved=0"><i>The Case for Split Ground Planes</i></a><i><span face="Calibri, sans-serif"><span style="font-size: 14.6667px;">.</span></span></i> Reprinted by permission of Signal Integrity Journal.</p><p>This section continues the discussion in <a href="https://blog.teledynelecroy.com/2023/01/signal-return-paths-signal-and-power.html" target="_blank">Signal Return Paths</a> of the equation,</p><p><span style="font-size: medium; text-align: center;">Z = R + j𝛚L</span></p><p>Where:</p><p>Z is the loop impedance of the current loop path, </p><p>R is the series resistance of the loop and </p><p>L is the loop inductance of the path.</p><p>. . .</p><p>At low frequency, when the loop impedance is dominated by the R term, the current distribution in the return plane is NOT driven by the loop impedance, it is driven by the loop resistance. In the signal path, the current will spread out uniformly as any filament path in the signal conductor will have roughly the same resistance.</p><p>But the current filaments in the return path with the lowest R will be those which are shortest. This means that return currents will take the shortest paths, independent of the signal paths. As frequency increases, the return current will redistribute to transition from the path of lowest R to the path of lowest L. <span></span></p><a name='more'></a><p></p><p>This was demonstrated in a simple experiment. A coax cable was shorted at the far end so that a DC current loop, driven by a function generator, would flow from the signal conductor and back through the return. At the front of the coax, the shield, which carries the return current, was shorted between the front of the coax and the back end of the coax. This is shown in Figure 3.</p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXAxOutV7g7meaAL9RmKCRJO1q157UF5YszzX6nrZF6dMIzBpSL8-Wtt3h_7kf52BqmKkltcHdeJSXKIgVtHl_JgFtUT9q3X_bvzaLCNQCnboCKDDiflCD9iR8hEauFWzafep7AGqN2_vaszWCbbxli18NVs2XgMHWyADMBQgrw4SfC6UTMPYwodhtnA/s726/SplitGround_Fig4.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="726" data-original-width="667" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXAxOutV7g7meaAL9RmKCRJO1q157UF5YszzX6nrZF6dMIzBpSL8-Wtt3h_7kf52BqmKkltcHdeJSXKIgVtHl_JgFtUT9q3X_bvzaLCNQCnboCKDDiflCD9iR8hEauFWzafep7AGqN2_vaszWCbbxli18NVs2XgMHWyADMBQgrw4SfC6UTMPYwodhtnA/s320/SplitGround_Fig4.png" width="294" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. Measured return current in the<br />shunt path dropping off above 10 kHz, <br />measured with a Teledyne LeCroy <br />WavePro® HD oscilloscope.</span></td></tr></tbody></table>At DC, the return current will flow through the shunt between the front and back of the shield, which is a lower resistance path, instead of flowing all the way down the shield to the far end where the signal and return currents are shorted together. <p></p><p>To measure the current that flows through this path, a Hall effect current clamp was placed around this shunt path. This measures the current flowing through this specific path. The function generator was used to drive a constant 60 mA amplitude of sine wave current through the coax cable and the frequency swept from 1 kHz to 10 MHz. The currents were measured with the Hall effect current probe and a <a href="https://teledynelecroy.com/waveprohd/" target="_blank">Teledyne LeCroy WavePro HD </a>12-bit, 8 GHz bandwidth scope.</p><p>At low frequency, all the return current flowed through the shunt path. But, as frequency increased, less current flowed through the shunt and more current flowed along the higher resistance, but lower loop inductance path of the coax shield, with the return current in close proximity to the signal current. Figure 4 shows the measured current amplitude in the signal-return loop at the far end, flat with frequency, and the measured current amplitude in the shunt, which drops off with a 1-pole response, above about 10 kHz. </p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguzRLOIP5FlwFUxr7UVZyGRzU1XKJahNaqRPhIDd7ISedO1L6BV_QxKseKcY7e5JEftXTTI9wM9OfoeF3k-6DkPxmK7BmsY6Dv65aJKn6B5l874ezAYi6K0tzVwLYuioAJb8iW4-_IhYLIeLY0T8O3awJWTE-s30-1NYETMWa3CnMq-yEQSZxjgbeqkQ/s915/SplitGround_Fig5.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="669" data-original-width="915" height="234" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguzRLOIP5FlwFUxr7UVZyGRzU1XKJahNaqRPhIDd7ISedO1L6BV_QxKseKcY7e5JEftXTTI9wM9OfoeF3k-6DkPxmK7BmsY6Dv65aJKn6B5l874ezAYi6K0tzVwLYuioAJb8iW4-_IhYLIeLY0T8O3awJWTE-s30-1NYETMWa3CnMq-yEQSZxjgbeqkQ/s320/SplitGround_Fig5.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 5 Measured step current response through <br />the shunt path with a 10-90 rise time of 32 usec, <br />measured with a Teledyne LeCroy <br />WavePro HD oscilloscope.</span></td></tr></tbody></table>This illustrates that above about 10 kHz, all the return current will always flows in the path directly adjacent to the signal current to reduce the loop inductance of the signal-return path. But, equally important, the return currents below about 10 kHz will always flow in the path for lowest resistance. <p></p><p>The transient step response of the current flowing through the shunt path will be a 1-pole response with a pole frequency about 10 kHz. This is an effective RC time constant of about 16 usec. This would result in a 10-90 rise time of about 32 usec. This is what is measured in the step response of the current through the shunt path, shown in Figure 5.</p><p><br /></p><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2023/01/signal-return-paths-signal-and-power.html" target="_blank">Signal Return Paths</a></div><div><div><a href="https://blog.teledynelecroy.com/2022/01/transmission-lines-for-oscilloscope.html" target="_blank">Transmission Lines for Oscilloscope Users, Part 1</a></div><div><a href="https://blog.teledynelecroy.com/2014/08/go-back-to-school-on-signal-integrity.html" target="_blank">Go Back to School on Signal Integrity</a></div></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-25431500682797408462023-01-16T08:00:00.023-05:002023-02-09T08:21:37.638-05:00Signal Return Paths: A Signal and Power Integrity Tutorial<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiu07kqtYJ-5QdcS2BSy9c5j4o3qn-88LrOBPuRR1siIIJpaVs34m5klc5Ttclp02twVB2TAI6mri_mthLGeEoGShRNYObtYXKxbMtRn7FkMVjtm3L953k2fXVH-n57sEhvcNFhMIPmnLtsuPYKcHsv3KVUwFJ5a4QV78wS6d3M6of1DbTaqIRZBu3Bjg/s955/SplitGround_Fig1.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="636" data-original-width="955" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiu07kqtYJ-5QdcS2BSy9c5j4o3qn-88LrOBPuRR1siIIJpaVs34m5klc5Ttclp02twVB2TAI6mri_mthLGeEoGShRNYObtYXKxbMtRn7FkMVjtm3L953k2fXVH-n57sEhvcNFhMIPmnLtsuPYKcHsv3KVUwFJ5a4QV78wS6d3M6of1DbTaqIRZBu3Bjg/s320/SplitGround_Fig1.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. Current distribution in the signal and <br />return conductors at three different frequencies. <br />The current redistribution at higher frequency <br />is driven by the currents taking filament paths <br />with the lowest loop inductance. </span></td></tr></tbody></table>The following is excerpted from Professor Eric Bogatin's article in the Signal Integrity Journal, <a href="https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.signalintegrityjournal.com%2Farticles%2F2982-the-case-for-split-ground-planes&data=05%7C01%7Cwtyler%40horizonhouse.com%7C5ed90a35003747eb05e508db09e31fe2%7C85f2fc98a3c44064815d1efc67da1928%7C0%7C0%7C638114643337382115%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=j%2BfqAZUuEKOAzlr5Vd5bkNCXxXh03S%2FQNQ1vOSN9YuM%3D&reserved=0"><i>The Case for Split Ground Planes</i></a><i><span face="Calibri, sans-serif"><span style="font-size: 14.6667px;">.</span></span></i> Reprinted by permission of Signal Integrity Journal.<p></p><p>. . .</p><h3 style="text-align: left;">Why Continuous Return Path Planes</h3><p>The first step in engineering interconnects to reduce noise is to provide a continuous, low impedance return path to control the impedance, which controls reflection noise, and reduce the cross talk between signals that also share the same return conductor. </p><p>A wide, continuous ground plane adjacent to a signal trace will be the lowest cross talk configuration. Anything other than a wide plane means more cross talk between signal paths sharing this return conductor. This means, never add a split or gap in the return path. You would run the risk of a signal trace inadvertently crossing this discontinuity.</p><p>If a signal crosses over a split ground plane, there are two effects which compound each other. Crossing a split creates a higher impedance path for return currents that must cross the split and forces return currents from multiple signals to overlap through the same, higher impedance, common path. <span></span></p><a name='more'></a><p></p><p>This creates the trifecta of problems: reflections from the return path discontinuity, ground bounce from the higher inductance return path, and EMI from the difference in potential between the two regions of the planes in which the return currents flow. This is why it is never a good idea to add a split in the ground return plane. You take too big a risk of signals routed crossing this split. </p><p>However, there is one potential, minor problem a split ground plane solves, provided the split or gap in the return plane is ALWAYS parallel to the signal path, and return currents do not cross this gap. It is cross talk from resistive coupling. </p><h3 style="text-align: left;">Where Return Currents Flow</h3><p>The path return currents take in a ground plane depends on the routing of the signal paths. The signal and return paths cannot be considered separately. They are linked together. The path the currents take in a signal and return conductor are dictated by the path of lowest loop impedance. If there were a path the signal-return current took that was lower impedance, there would be a lower voltage drop along that path and currents would flow from the higher voltage paths to the lower voltage paths until all conductors, normal to the direction of propagation, are at an equipotential. </p><p>This means that of the multiple paths signal-return currents could take, the currents will flow in the path to minimize the loop impedance of all possible paths. </p><p>Usually, the signal trace is narrow and confines the signal current to a very specific path. The return current can flow in the adjacent ground plane anywhere, unconstrained except for the plane edges. It will take the path so that the loop impedance of the signal-return path is minimized. To first order, the impedance of the signal-return path is frequency dependent and related to:</p><p style="text-align: center;"><span style="font-size: medium;">Z = R + j𝛚L</span></p><p>In this equation, </p><p>Z is the loop impedance of the current loop path,</p><p>R is the series resistance of the loop and</p><p>L is the loop inductance of the path</p><p>Imagine the signal-return path currents as composed of continuous current filaments taking any path they can down the interconnect. The filaments that have the most current are those with the lowest loop impedance. The more current flowing down one of these filaments, the higher the voltage drop across this series impedance. This pushes more current into adjacent higher impedance filaments until the cross section of current distribution, balanced by the impedance of each filament and the amount of current in each filament, create an equipotential across the direction of propagation. </p><p>There will always be a frequency, above which the <span style="text-align: center;">𝛚L</span> term dominates and the current paths are driven by the path of lowest loop inductance. This is the region we refer to as the skin depth region. The current redistribution for lowest loop inductance is what drives the skin depth effect. </p><p>The lowest impedance path is when the currents within the same conductor are farthest apart, to reduce the partial self-inductances, but are closest together between the signal and return paths, to increase the partial mutual inductances. This is illustrated in Figure 1, showing the current distributions in a simple microstrip at 1 MHz, 10 MHz and 100 MHz, simulated with Ansys Q2D. </p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjidsFrgWKOK2PTn_zmKZJhNFmBmU3r2BS8rXq3WAbMwRnULliizy8bBGHmCanQLkFgeXQMYmsbiFyjIo29kt4gSqzR3d63v79HE0n8xPzGQ-E5_jrutRMkdTwFdCxAyKrcV4-MjSzKZIf0vmOgUOFsBQ5vNWTrvaUknRrFc146BJijiSCJKWPlnIMW3g/s500/SplitGround_Fig2.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="375" data-original-width="500" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjidsFrgWKOK2PTn_zmKZJhNFmBmU3r2BS8rXq3WAbMwRnULliizy8bBGHmCanQLkFgeXQMYmsbiFyjIo29kt4gSqzR3d63v79HE0n8xPzGQ-E5_jrutRMkdTwFdCxAyKrcV4-MjSzKZIf0vmOgUOFsBQ5vNWTrvaUknRrFc146BJijiSCJKWPlnIMW3g/s320/SplitGround_Fig2.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. Current flow in the return path at 1 MHz, <br />when the signal path changes.</span></td></tr></tbody></table>This means that in the high frequency regime, the return currents are always flowing directly underneath the signal currents. The path underneath the signal currents is always the lowest loop inductance path. Any current filaments away from this path will have a higher impedance and a higher voltage drop and flow to the lower voltage filaments, directly under the signal. <p></p><p>As the signal conductor meanders over the surface of the ground plane, the return currents will follow right along under the signal path. Figure 2 shows an example of the return current distribution in a plane when the signal conductor changes direction, simulated for 1 MHz frequency components. </p><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2022/01/transmission-lines-for-oscilloscope.html" target="_blank">Transmission Lines for Oscilloscope Users, Part 1</a></div><div><a href="https://blog.teledynelecroy.com/2014/08/go-back-to-school-on-signal-integrity.html" target="_blank">Go Back to School on Signal Integrity</a></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-3344316638812162602022-11-28T08:00:00.005-05:002022-11-30T09:45:05.851-05:00New 60 V Offset Power Rail Probes Offer the Capability Needed for 48 V Power Integrity Analysis<p></p><div class="separator" style="clear: both; text-align: center;"><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhI8645mrq8hzW9ASP9bQmRgmBU-gERAX8BLrRtGfTC679t8Ghi2zp2Ov12T1DuaPgM8J3q8GciKflxA5XJDLA80YBQjCwuhi32QGcqKpyhdETlCQFzgQjRquebGEqRaCLeXcNMkvlKBXIstxTtNcKqpYmLn5y-jkf5W-1J4gz-5Z4pJYEckwQfUOHEtQ/s1016/rp4060-insert-cover.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="RP4060 Rail Probe" border="0" data-original-height="1016" data-original-width="825" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhI8645mrq8hzW9ASP9bQmRgmBU-gERAX8BLrRtGfTC679t8Ghi2zp2Ov12T1DuaPgM8J3q8GciKflxA5XJDLA80YBQjCwuhi32QGcqKpyhdETlCQFzgQjRquebGEqRaCLeXcNMkvlKBXIstxTtNcKqpYmLn5y-jkf5W-1J4gz-5Z4pJYEckwQfUOHEtQ/w260-h320/rp4060-insert-cover.png" title="RP4060 Rail Probe" width="260" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1. The RP2060 and RP4060<br />build on the legacy of the RP4030 power<br />rail probe. The new probes are ideally<br />suited to working with the new 48 Vdc <br />power structures.</td></tr></tbody></table></div>In 2016, Teledyne LeCroy first offered the RP4030 Power Rail Probe, which was designed to enable engineers to probe a low-impedance, low-voltage DC power/voltage rail signal without loading the device under test (DUT). It provided ±30 V of probe offset to allow a DC power/voltage rail signal to be displayed in the vertical center of the oscilloscope regardless of the gain (sensitivity) setting.<p></p><p>Recently, we released two, new power rail probes that build on those capabilities—the 2 GHz <a href="https://teledynelecroy.com/probes/active-voltage-rail-probe/rp2060" target="_blank">RP2060</a> and 4 GHz <a href="https://teledynelecroy.com/probes/active-voltage-rail-probe/rp4060" target="_blank">RP4060</a>. Both probes feature:</p><p></p><ul style="text-align: left;"><li>±60 V Offset Capability</li><li>±800 mV Dynamic Range</li><li>50 kΩ DC Input Impedance (for low loading of low-impedance power rails)</li><li>1.2:1Attenuation (for low additive noise)</li><li>MCX-terminated cable with a variety of board connections: 4 GHz*-rated MCX PCB mount; <br />4 GHz* solder-in; 3 GHz* coaxial cable to U.FL PCB mount; optional 500 MHz browser<br /></li></ul><span style="font-size: x-small;">* Bandwidths listed are for the 4 GHz RP4060. Maximum bandwidth when used with RP2060 is 2 GHz.</span><p></p><h3 style="text-align: left;">Why the New Probes?</h3><p>One driver of the new release is the increase in the number and size of data centers needed to support cloud computing and other data-intensive applications, and the new power architectures they require. The new rail probe is designed to ideally meet the needs of
engineers working with power rails rated up to 48 Vdc.<span></span></p><a name='more'></a><p></p><p>To power individual servers in the racks
that make up data centers, traditional “server farms” would step down power to
the 12 Vdc needed to input to the server, where within
the server it would be further stepped down to the 5 V, 3 V, 1 V
or less needed to power the many individual chips. In the process, much energy
is lost to heat, which in turn requires more energy to cool, raising costs. The
average data center today uses an average of 3 kW to 5 kW of electricity per rack.</p>
<p class="MsoNormal">New, more efficient architectures use a 48 Vdc distribution
voltage right at the server, where new types of power modules and digital
controllers step it down to the much smaller voltages needed by other subsystems.
Engineers designing such systems therefore need to probe DC voltages anywhere
from 1 V or less to 48 V. Also, because it is a DC voltage, <a href="https://teledynelecroy.com/oscilloscope/hdo.aspx" target="_blank">high resolution oscilloscopes</a> and probes with very high voltage offset are needed to see the
very small amounts of ripple and other types of noise that may be present on a
power rail, pointing to potential problems in the system. By increasing
the 30 V offset of the legacy RP4030 Power Rail Probe to a comfortable 60 V,
the new RP2060 and RP4060 Power Rail Probes provide the voltage range, offset
and sensitivity needed for the new 48 V power structure.</p><h3 style="text-align: left;">How We Do It</h3><p class="MsoNormal">The input is through a high-bandwidth SMA connector, terminated to ground with a 50 kΩ resistor in parallel with a 0.1 μF capacitor. This provides high input impedance near DC and low input impedance at high frequencies―highly desirable for low-impedance DC power rail probing. A two- stage offset DAC provides ± 60 V range. This permits the offset value to be set with high accuracy (0.1% ±3 mV). The output is through a BNC connection to the Teledyne LeCroy ProBus interface into a 50 Ω oscilloscope termination. An Auto Zero grounding switch permits Auto Zero of the DC value at any time without having to disconnect the probe from the device under test (DUT). </p><h4 style="text-align: left;">Also see:</h4><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2021/10/measuring-dead-time-in-48-v-power.html" target="_blank">Measuring Dead Time in 48 V Power Converters, Part 2: Dynamic Measurements</a></p><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2021/08/measuring-dead-time-in-48-v-power.html" target="_blank">Measuring Dead Time in 48 V Power Converters, Part 1: Static Measurements</a></p><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2020/08/fundamentals-of-power-integrity_28.html" target="_blank">Fundamentals of Power Integrity: Characterizing PDN Noise</a></p><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2020/09/fundamentals-of-power-integrity-self.html" target="_blank">Fundamentals of Power Integrity: Self-aggression Noise</a></p><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2020/09/fundamentals-of-power-integrity-board.html" target="_blank">Fundamentals of Power Integrity: Board Pollution</a></p><p class="MsoNormal"><br /></p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-65295803539610712562022-11-21T08:00:00.156-05:002022-11-21T08:00:00.173-05:00Oscilloscope Serial Data Measurements and DAC: Trigger, Decode, Measure/Graph and Eye Diagram Software<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlqe0WI_-ygLmXLM8Inx-BLDK4za4C25AHacC2uqCQ2FUj9LMckKRyEqg7MLkLQqeuKvTndFl0ScRnV5M3bhUyzA5ecWB5Y4hCNakq9adX4JgAC3uJNq2XslQt1bIub1ZCbN-oDMZc41UsOSbyPG2TPf6_xbOCWrWf1JDcw2EApTrGr_u7o1hfe8reFA/s697/TDME_Parameters.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Table of serial bus measurement parameters" border="0" data-original-height="494" data-original-width="697" height="227" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlqe0WI_-ygLmXLM8Inx-BLDK4za4C25AHacC2uqCQ2FUj9LMckKRyEqg7MLkLQqeuKvTndFl0ScRnV5M3bhUyzA5ecWB5Y4hCNakq9adX4JgAC3uJNq2XslQt1bIub1ZCbN-oDMZc41UsOSbyPG2TPf6_xbOCWrWf1JDcw2EApTrGr_u7o1hfe8reFA/w320-h227/TDME_Parameters.png" title="Serial bus measurements" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1. Serial bus measurements made available<br />with "TDME" and "TDMP "decoder options.</td></tr></tbody></table>All <a href="https://teledynelecroy.com/oscilloscope/" target="_blank">Teledyne LeCroy oscilloscopes</a> support a rich set of standard waveform measurement parameters, but the installation of any "TDME" or "TDMP" serial decoder software option adds special parameters designed for measuring serial data buses. Besides automating the measurement of serial bus timing, these parameters allow you to access encoded serial data and extract it to analog values for what is essentially a Digital-to-Analog Converter (DAC)!<div><br /><p></p><h3 style="text-align: left;">What’s in a Name?</h3><p>Teledyne LeCroy has adopted the convention of using a key in the name of our <a href="https://teledynelecroy.com/options/default.aspx?categoryid=12&groupid=88&capid=102&mid=506" target="_blank">serial trigger and decode products</a> that tells you what capabilities they offer. The “<b>M</b>E” or “<b>M</b>P” in the name of a Teledyne LeCroy serial decoder option (e.g., <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=474&groupid=88" target="_blank">CAN FDbus TD<b>M</b>E</a> or <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=684&groupid=88" target="_blank">USB4-SB TD<b>M</b>P</a>) refers to "<b>M</b>easure/Graph and Eye Diagram" or "<b>M</b>easure/Graph and Physical Layer Tests." All these options include the following 10 serial bus measurements. Physical Layer Test options will also include measurements designed specifically to meet the requirements of the standard.<span></span></p><a name='more'></a><p></p><h3 style="text-align: left;">Measure Serial Bus Performance and Timing</h3><p>These parameters are key to understanding the performance of digital bus traffic.</p><p><b>Bus Load</b> computes the load of selected messages on the bus (as a percent of total). </p><p><b>Message Bitrate</b> computes the bitrate of selected messages.</p><p><b>Number of Messages</b> computes the total number of messages in the decoding that meets filter conditions.</p><p><b>Message to Message</b> computes the time from the start of the first message that meets filter conditions to the start of the next message in the same or different decoding that meets filter conditions.</p><p><b>Delta Message</b> computes the time difference between two messages on a single decoded bus line. </p><p><b>Time at Message</b> computes the time from acquisition trigger to the start of each message that meets filter conditions.</p><p style="text-align: left;"><span style="font-weight: normal;">These parameters let you measure the decoded digital data against the state of a second, analog signal. They are especially useful for measuring serial data against a clock signal or a power rail voltage.</span></p><p><b>Message to Analog</b> computes the time from the start of the first message that meets any filter conditions to an amplitude/voltage level on an analog signal.</p><p>Likewise, <b>Analog to Message</b> computes the time from an amplitude/voltage level on an analog signal to the start of the first message that meets any filter conditions. </p><h3 style="text-align: left;">Convert Digital Message to Analog Values (Serial DAC)</h3><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSxWMq1iIjtwYNq1pEsDA4jVS_BcKuUuunZ3WEWBRI2QCYuEpviFQbs-OLoVlWTWTA19PTy_0_1EM4U4_I_yJx_hvy5cURk70C4ezVlxXmjfuANT-vpSDBwtDPbkbsXP5lIji5eemu70kHIL9Gy8dC8qYr0eEIAZRYJKyZwXxGp62ZBMD9GCbPnaJEKg/s852/SensorSerialFig4.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Interface selections for digital-to-analog converter using Teledyne LeCroy serial TDME options" border="0" data-original-height="827" data-original-width="852" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSxWMq1iIjtwYNq1pEsDA4jVS_BcKuUuunZ3WEWBRI2QCYuEpviFQbs-OLoVlWTWTA19PTy_0_1EM4U4_I_yJx_hvy5cURk70C4ezVlxXmjfuANT-vpSDBwtDPbkbsXP5lIji5eemu70kHIL9Gy8dC8qYr0eEIAZRYJKyZwXxGp62ZBMD9GCbPnaJEKg/w320-h311/SensorSerialFig4.png" title="Serial DAC" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 2. Example parameter setup for serial <br />DAC of embedded sensor data.</td></tr></tbody></table>Many serial buses carry sensor or other types of data whose properties may be best viewed as an analog waveform. These very special parameters allow you to “extract” the digitally encoded analog data, convert it back to analog values, and plot it as an analog waveform (serial DAC). <p></p><p><b>Message to Value</b> extracts a selected portion of the decoded data to a measurement parameter location, with optional conversion of the value to a different scale and/or unit. The extracted data may be selected by ID and/or data field position. The parameter can in turn be plotted as a histogram, track or trend graph, or used in a Math on Parameters formula.</p><p><b>View Serial Encoded Data as Analog Waveform</b> sets up a Message to Value parameter and track graph in one step. </p><p>An example of using these parameters as a serial DAC is described in <a href="https://blog.teledynelecroy.com/2021/09/correlating-sensor-and-serial-data-in.html" target="_blank">Correlating Sensor and Serial Data in Complex Embedded Systems</a>, where digitally encoded fan speed data is extracted from decoded serial messages using the Message to Value parameter, converted to temperature, then plotted as a track waveform showing the temperature fluctuations over time. A great advantage of using the TDME software for this is that the extracted analog waveform is time synchronous with the decoding, allowing you to view them side by side and correlate events.</p><p>Besides plotting the extracted values as a graph, Measure to Value can act as a “pass through” of those values to other measurement parameters or math functions by selecting the Message to Value parameter as a source. </p><h3 style="text-align: left;">Easily Graph Serial Data Measurements</h3><p>Any serial data measurements, not just the serial-analog parameters, can be plotted as a <a href="https://blog.teledynelecroy.com/2015/02/using-histograms-part-i.html" target="_blank">histogram</a>, <a href="https://blog.teledynelecroy.com/2022/03/oscilloscope-basics-when-to-use-track.html" target="_blank">track </a>or <a href="https://blog.teledynelecroy.com/2022/04/oscilloscope-basics-when-to-use-trend.html" target="_blank">trend</a> graph for statistical analysis. The output graph can be selected right on the dialog where the parameter is set up.</p><p></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizUn9IwYjy-fqVJmV8jtw5v2Zzx9JGOWtJ4hqFfnZsw1fb5eaPA8bqlC9eLReeY8AiNHFfnu2hvNbvxPkiHqe6Tk2TsOnW3D91MwBZlYjXYnX6eAiUt3I7-md2W1F2Zpp2IHmPsQp2nzMmLmoa1Uki7_cKHdhyQxjvs4gqPioN_XbLXeYhDkkO3GF__Q/s1278/TDME_Msg2ValueSetup.png" style="margin-left: auto; margin-right: auto;"><img alt="Serial bus measurement set up dialog in Teledyne LeCroy "TDME" options" border="0" data-original-height="206" data-original-width="1278" height="103" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizUn9IwYjy-fqVJmV8jtw5v2Zzx9JGOWtJ4hqFfnZsw1fb5eaPA8bqlC9eLReeY8AiNHFfnu2hvNbvxPkiHqe6Tk2TsOnW3D91MwBZlYjXYnX6eAiUt3I7-md2W1F2Zpp2IHmPsQp2nzMmLmoa1Uki7_cKHdhyQxjvs4gqPioN_XbLXeYhDkkO3GF__Q/w640-h103/TDME_Msg2ValueSetup.png" title="Serial Measure/Graph Set Up Dialog" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 3. Graphs can be selected right on the dialog where measurement is set up.</td></tr></tbody></table><br /><b>Histogram </b>plots a bar chart of the measured values, which shows the statistical distribution of measurements.<p></p><p><b>Track </b>acts like a strip-chart recorder, plotting one measurement value per digital sample. It is the track graph of extracted serial data that can be used to recreate an original analog waveform.</p><p><b>Trend </b>plots the history of change in a parameter, allowing you to see if variation is periodic or random.</p><p>The use of graphs for statistical analysis is described in <a href="https://blog.teledynelecroy.com/2021/10/measuring-dead-time-in-48-v-power.html" target="_blank">Measuring Dead Time in 48 V Power Converters, Part 2: Dynamic Measurements</a>.</p><h3 style="text-align: left;">Filter Measurements by Device, Data Types/Values or Acquisition Time</h3><p>Any serial bus measurements and graphs can be performed on all decoded data, or on only data that meets your filter criteria, allowing you to target the measurements and graphs to particular devices or transmission types.</p><p>The first level of filtering, the selection of packets by device ID or ID plus data pattern found in the decoding, is done as part of the initial parameter set up. Only those packets matching the filter criteria are included in the measurement. Filtering is not required: the selection of “Any” will apply measurements to the full decoding.</p><p>The next level is to filter a particular column of the measurement results table to display only values that meet a set of Boolean criteria. This method is demonstrated in <a href="https://blog.teledynelecroy.com/2022/10/oscilloscope-measurements-of-10base-t1s.html" target="_blank">Oscilloscope Measurements of 10Base-T1S Auomotive Ethernet PLCA Cycle Timing</a>, where by filtering the table to show only packets with the value BEACON in the transmission Type column, the serial measurements reflect the performance of the Master node on the bus. </p><p>If you filter the Time column, you can apply the measurements only to a particular acquisition time.</p><p>Finally, the “Apply to Zoom” feature acts as another layer of filter, focusing the measurements on only those packets that meet all the above criteria <i>and </i>are currently selected from the result table. The act of selecting a row of the table creates a “zoom” of that region, and if “Apply to Zoom” is checked, measurements (and eye diagrams) apply to only the active zoom trace, rather than the entire decoding. In this way, measurements can be made packet to packet as you step down each row of the table. </p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-vocCJNuxulJ1n7D8nuu5keAwP9TyeQkKxMp6IvWlC1d4LLAyWq1jypoIYBQ3dZiVKkLNYqfWK_StBKfWf5ot-Txzd7YWemgR3I0VHYClK3lJ973yILcPNS8BNvBKM_EMTSrp_5z-7grfEFbnJVsVD5ZXwDhwjsnrS0kLOT-jfZPmo4fIJKGDSpu_vw/s2920/MECompEyes.png" style="margin-left: auto; margin-right: auto;"><img alt=""Apply to Zoom" example, showing redrawn eyes and recalculated measurements as each row of result table is selected." border="0" data-original-height="661" data-original-width="2920" height="144" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-vocCJNuxulJ1n7D8nuu5keAwP9TyeQkKxMp6IvWlC1d4LLAyWq1jypoIYBQ3dZiVKkLNYqfWK_StBKfWf5ot-Txzd7YWemgR3I0VHYClK3lJ973yILcPNS8BNvBKM_EMTSrp_5z-7grfEFbnJVsVD5ZXwDhwjsnrS0kLOT-jfZPmo4fIJKGDSpu_vw/w640-h144/MECompEyes.png" title="Apply to Zoom" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 4. "Apply to Zoom" redraws eyes and recalculates measurements as <br />different packets within the same acquisition are selected from the table.</td></tr></tbody></table><p><b>Note:</b> Eye diagrams, discussed in <a href="https://blog.teledynelecroy.com/2022/11/usb-serial-decode-software-usb-eye.html" target="_blank">Serial Trigger, Decode, Measure/Graph and Eye Diagram: Oscilloscope Eye Diagrams for Debug</a>, are another visualization tool included with “ME” and “MP” options. Although they do not graph measurement results, eye diagrams can be used to visually assess the signal integrity of a serial data stream.</p><h3 style="text-align: left;">Easily Navigate the Decoded Acquisition</h3><p>The same interactive table that can be used to “zoom” and filter data can also be used as a way to navigate the acquisition, allowing you to quickly bring focus to regions of the total acquisition simply by selecting a row of the table. </p><p>If more than one decoder is active, the decoded packets are sequentially interleaved on the table, so you can quickly see the relative timing of two buses or messages in two protocols riding on one bus (the image below shows USB-PD and DP-Aux traffic over a single USB-C connection). Touching the Index cell let's you "drop-in" the detailed decoding.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0X-4rnGCZHoskVk5OcK8Ucpm_C9i760t4K9p_pzrg_i568WnCtN2JU72RDJjBQIAFO21IYaFakkT2xcJuYDF9xzTTscj-uwsJHTeds11kQ-qXDClU8L6OEHIxkMd4XeLOwJxto4I5GT82/s964/USBPD-DPAUX+MtoM.PNG" style="margin-left: auto; margin-right: auto;"><img alt="Interleaved table of decoder results show relative timing between packets from different decodings. Individual details can be "dropped in."" border="0" data-original-height="379" data-original-width="964" height="252" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0X-4rnGCZHoskVk5OcK8Ucpm_C9i760t4K9p_pzrg_i568WnCtN2JU72RDJjBQIAFO21IYaFakkT2xcJuYDF9xzTTscj-uwsJHTeds11kQ-qXDClU8L6OEHIxkMd4XeLOwJxto4I5GT82/w640-h252/USBPD-DPAUX+MtoM.PNG" title="Interleaved Decoder Result Table" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 5: P1 Message to Message parameter shows timing between interleaved USB-PD and DP-Aux messages, while the details of row 99 are "dropped" into the table display by touching the Index cell.<br /></span></td></tr></tbody></table><p>Teledyne LeCroy Serial TDME and TDMP options are the Gold Standard in serial bus analysis software, giving you unparalleled ability to access and analyze the content of serial data messages. </p><p>To learn more about how you can apply serial data measurements and graphs, see our free, on-demand webinar, <a href="https://go.teledynelecroy.com/l/48392/2022-07-06/8hv94v?&utm_source=website&utm_medium=events-page&utm_campaign=22-08-25-oscilloscope-coffee-break-webinar-8&utm_content=on-demand" target="_blank">How to Use an Oscilloscope as a Serial Digital-to-Analog Converter (DAC) for Validation and Debug</a></p><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2022/11/usb-serial-decode-software-usb-eye.html" target="_blank">Serial Trigger, Decode, Measure/Graph & Eye Diagram (TDME) Software: Oscilloscope Eye Diagrams for Debug</a></div><div><br /></div><div><a href="https://blog.teledynelecroy.com/2021/09/correlating-sensor-and-serial-data-in.html" target="_blank">Correlating Sensor and Serial Data in Complex Embedded Systems</a></div><div><br /></div><div><a href="https://blog.teledynelecroy.com/2021/09/correlating-low-to-high-speed-events-in.html" target="_blank">Correlating Low to High-Speed Events in Complex Embedded Systems</a></div><p><a href="https://blog.teledynelecroy.com/2021/03/tdme-primer-automated-usb-c-timing.html" target="_blank">TDME Primer: Automated Timing Measurements of USB-C Protocols</a> </p><p><a href="https://blog.teledynelecroy.com/2021/10/measuring-dead-time-in-48-v-power.html" target="_blank">Measuring Dead Time in 48 V Power Converters, Part 2: Dynamic Measurements</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/getting-most-out-of-your-oscilloscope_30.html" target="_blank">Getting The Most Out Of Your Oscilloscope: Cursors and Parameters</a></p></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-31882172336894020312022-11-14T08:00:00.055-05:002022-11-14T10:42:14.542-05:00SDAIII and QualiPHY Software: Oscilloscope Eye Diagrams for Compliance and Debug<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhhUZp92GkK17538whKvWZXgW5p9kTgdASgrjXFvvIYGx7nRv5oEkDzaVkpV5JSYqFxTsDFjeHILTGhPMhJeadUNZQ5PV4vVYmqHiyTDfibYzJV-PbiR7hRsHlxQ_1dq5imJ-SlzbQ34b5xVxtXBfmkk26hxPIiwyi-aQt-bQiYqxDCg1HifIF2pfMhPA/s2026/USBEye_Pt2Fig1.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1125" data-original-width="2026" height="178" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhhUZp92GkK17538whKvWZXgW5p9kTgdASgrjXFvvIYGx7nRv5oEkDzaVkpV5JSYqFxTsDFjeHILTGhPMhJeadUNZQ5PV4vVYmqHiyTDfibYzJV-PbiR7hRsHlxQ_1dq5imJ-SlzbQ34b5xVxtXBfmkk26hxPIiwyi-aQt-bQiYqxDCg1HifIF2pfMhPA/s320/USBEye_Pt2Fig1.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1. SDAIII enables eye diagrams and eye<br />measurements of four lanes of streaming data.</td></tr></tbody></table>Besides the <a href="https://blog.teledynelecroy.com/2022/11/usb-serial-decode-software-usb-eye.html" target="_blank">serial TDME and TDMP options</a> discussed earlier, there are other ways to generate eye diagrams on your Teledyne LeCroy oscilloscope for compliance testing and debug.<p></p><h3 style="text-align: left;">SDAIII Serial Data Analysis Software</h3><p><a href="https://teledynelecroy.com/options/productseries.aspx?mseries=405&groupid=103" target="_blank">SDAIII</a> offers the most comprehensive eye diagram capabilities for Teledyne LeCroy oscilloscopes, with tools for optimizing the displayed eye that are especially useful to high-speed serial data analysis.<span></span></p><a name='more'></a><p></p><p>SDAIII eye diagrams are created without using a trigger. This is done using a phase locked loop (PLL) to implement software clock recovery to learn the clock period. Once the clock period is determined, the data record is divided into segments somewhat larger than the clock period. The samples are positioned relative to the recovered clock edge times, and the segments are overlayed in a persistence display by aligning the clock delimited boundaries. Since the unit interval is determined from the recovered clock and not from the oscilloscope's trigger position, this method does not include jitter from any trigger circuit.</p><p>For serial data protocols supporting spread spectrum clocking to reducing EMI levels, the PLL clock recovery technique has the advantage of being able to track the small shifts in the clock period and compensate for it. This results in the cleaner eyes in SDAIII. </p><p>With the multi-lane <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=405&groupid=103" target="_blank">SDAIII-CompleteLinQ</a> option, you can simultaneously generate up-to-four eye diagrams to compare upstream and downstream lanes of data, or the signal at both the transmitter and receiver, as shown in Figure 1.</p><p>The <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=234&groupid=103" target="_blank">Eye Doctor II</a> capabilities included with SDAIII-CompleteLinQ allow you to see the eye with or without different equalization, emphasis or deemphasis settings, or following the de-embedding of cables, probes and fixtures. Be aware that signal processing for these functions utilizes tapped delay line filtering and requires minimum signal lengths to implement. The number of unit intervals required is either two or eight UI, varying with specific settings. If the signal length is too short, a warning appears in the oscilloscope message field.</p><h3 style="text-align: left;">QualiPHY Compliance Test Software</h3><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiU0xstPh_cvHJVKpSivhZy9GJLgMB2ddWhoc9e7QDyVOYsS4sRqG6Yq4ooFfLf7HiFQ_j3_m2Crnx1XYHB21pA1b-_-gCE_FoaeL-2hZB4JowkxYA0hO3gn5b552fEtJPPmvgNiNfGd7qQNoShyf4-achkpfrToJwWVgvkJl-nq2Tz8QY9A3h0bLfF-Q/s1506/USBEye_Pt2Fig2.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="USB4 test report generated in QualiPHY" border="0" data-original-height="782" data-original-width="1506" height="166" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiU0xstPh_cvHJVKpSivhZy9GJLgMB2ddWhoc9e7QDyVOYsS4sRqG6Yq4ooFfLf7HiFQ_j3_m2Crnx1XYHB21pA1b-_-gCE_FoaeL-2hZB4JowkxYA0hO3gn5b552fEtJPPmvgNiNfGd7qQNoShyf4-achkpfrToJwWVgvkJl-nq2Tz8QY9A3h0bLfF-Q/w320-h166/USBEye_Pt2Fig2.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2: A sample QualiPhy report showing the <br />total jitter and eye diagram calibration <br />for USB4-Tx-Rx compliance testing.</span></td></tr></tbody></table>QualiPHY® test suites automate the creation of eye diagrams for each test that requires them as specified by CTS for the standard. Usually, an installation of SDAIII is required to provide the eye diagramming capabilities, while the QualiPHY software communicates the proper settings to SDAIII for the eye diagram views and measurements. For standards like PCI Express® that use SigTest or other third-party software to generate and measure eye diagrams for compliance testing, QualiPHY will interface with those applications as needed.<div><br /></div><div>Optional settings within QualiPHY enable you to pause the test sequence to view the resulting eye diagrams and measurements, or you can simply allow the tests to proceed to the final report of Pass/Fail results, interacting with the software only as required to change cables or the test mode of the DUT.<p></p><p>A typical QualiPHY test report showing eye diagram calibration results for USB4 is shown in Figure 2.</p><p>Teledyne LeCroy oscilloscope eye diagram capabilities offer a simple way to measure the signal integrity of serial data communications, whether the eye diagrams and measurements of packetized data in the serial TDME options, or the more sophisticated analysis available in SDAIII. </p><h4 style="text-align: left;">Also see:</h4><p style="text-align: left;"><a href="https://blog.teledynelecroy.com/2022/11/usb-serial-decode-software-usb-eye.html" target="_blank">Serial Trigger, Decode, Measure/Graph and Eye Diagram (TDME) Software: Oscilloscope Eye Diagrams for Debug</a></p><p><br /></p></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-57529157946558400182022-11-11T18:00:00.004-05:002022-11-14T12:26:57.994-05:00Serial Trigger, Decode, Measure/Graph & Eye Diagram (TDME) Software: Oscilloscope Eye Diagrams for Debug<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIin0fbgwbJI4ecqu6Et0DxN4NDhOEdWzbxmnCbS2swTzrRDddYtje_QJCATWZFgGWZybJVydkuyprmbj1woDpUdF2bocQNA_WbKk2L9QGtAy2Vj82Ns9vv42cLYjab1eGT5V43KQBwp98YNz34N8DGHWbCAuwkhka8b7lXdxakWKjnie6o4liOYNGIg/s1920/USBEye_Pt1Fig1.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Eye diagrams generated from two serial decodes." border="0" data-original-height="1080" data-original-width="1920" height="180" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIin0fbgwbJI4ecqu6Et0DxN4NDhOEdWzbxmnCbS2swTzrRDddYtje_QJCATWZFgGWZybJVydkuyprmbj1woDpUdF2bocQNA_WbKk2L9QGtAy2Vj82Ns9vv42cLYjab1eGT5V43KQBwp98YNz34N8DGHWbCAuwkhka8b7lXdxakWKjnie6o4liOYNGIg/w320-h180/USBEye_Pt1Fig1.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. Two eye diagrams generated from <br /></span>three active USB <span style="text-align: left;">serial decoders.<br />Click any image to enlarge it.</span></td></tr></tbody></table><p></p><p class="MsoNormal">The eye diagram is a general-purpose tool for analyzing the signal integrity of serial digital communications signals. It shows the effects of additive
vertical noise, horizontal jitter, duty cycle distortion, inter-symbol
interference, and crosstalk on a serial data stream. The vertical opening of
the eye is affected by these elements, as well as
gain differences between devices on the bus, so that the more problems with signal integrity, the more “sleepy” the eye appears. A wide open eye is
indicative of good signal integrity.<o:p></o:p></p><p>
</p><p class="MsoNormal">It is commonplace to use an oscilloscope with decoder
software to analyze the health of serial data streams, where the combination of
the electrical waveform and the link layer decoding shows if and where the
protocol breaks down at the physical layer, but an eye diagram can better show the <i>degree</i> of
signal interference that may be impacting the serial logic—especially if it
could be generated for particular devices or packets.<span></span></p><a name='more'></a><o:p></o:p><p></p><h3 style="text-align: left;">What's in a Name?</h3><div><p class="MsoNormal">Teledyne LeCroy has adopted the convention of using a key in
the name of our <a href="https://teledynelecroy.com/options/default.aspx?categoryid=12&groupid=88&capid=102&mid=506" target="_blank">serial data trigger and decode products</a> that tells you what
capabilities they offer. The “M<b>E</b>” or “M<b>P</b>”
in the name of a Teledyne LeCroy serial decode option (e.g., <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=474&groupid=88" target="_blank">CAN FDbus TDM<b>E</b></a>
or <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=684&groupid=88" target="_blank">USB4-SB TDM<b>P</b></a>) refers to "<b>M</b>easure/Graph and <b>E</b>ye Diagram" or "<b>M</b>easure/Graph and <b>P</b>hysical Layer Tests." These options can quickly generate and measure
an eye diagram of the decoded input signal for basic signal integrity testing. <o:p></o:p></p></div><h3 style="text-align: left;">Serial Decoders with Measure/Graph and Eye Diagram Capability</h3><p>All serial decode oscilloscope options create eye diagrams in accordance with the governing standards. They can be generated from NRZ or PAM signals and will show
either single or multiple eyes, accordingly.</p><p class="MsoNormal"><o:p></o:p></p><p>The basic concept for all the standards is to acquire a long data record and determine the clock rate of the acquired data so that the edge locations can be accurately located. For data protocols that use non-continuous bit streams in the form of data packets, the clock is determined as the mean clock period for each packet. Using the recovered clock period, the long record is sliced into segments that are slightly longer than the clock period, or Unit Interval (UI). These UIs are overlapped in a persistence display to create the eye (Figure 2).</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGIuMzsxcyKDKXRBY7pH0yH-FK58X18dmDFKWOpvpziBhVSjdQudTHBonbqsVa35_pc8cV-fRSejQHPz3Hs06cWpdJMVVFNzZwcIUeorCzTgLXAUY7qPoW5_i22f3h0uLPjc-QP-nKMDN6avKFGWaHLFOsS35nuq9zB9Psct_EskE2sFK3DxkUDH0IEQ/s1515/USBEye_Pt1Fig2.png" style="margin-left: auto; margin-right: auto;"><img alt="Segmentation of long acquisition to form eye diagram" border="0" data-original-height="747" data-original-width="1515" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGIuMzsxcyKDKXRBY7pH0yH-FK58X18dmDFKWOpvpziBhVSjdQudTHBonbqsVa35_pc8cV-fRSejQHPz3Hs06cWpdJMVVFNzZwcIUeorCzTgLXAUY7qPoW5_i22f3h0uLPjc-QP-nKMDN6avKFGWaHLFOsS35nuq9zB9Psct_EskE2sFK3DxkUDH0IEQ/w640-h316/USBEye_Pt1Fig2.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. To create an eye diagram, a long acquisition is segmented into short records with a duration slightly longer that the clock period of the serial data stream. The short records are overlaid into a persistence display forming the eye.</span></td></tr></tbody></table><p>The persistence display may use color-graded or analog (monochrome) persistence, according to the user's selection. </p><p>With color-graded persistence, each pixel is given a color based on the pixel's relative population and the selected Eye Saturation user setting. The color palette ranges from violet (least often occurring) to red (most often occurring). </p><p>With analog persistence, all pixels are the same color, but the pixel intensity (brightness) is based on the pixel’s relative population and the eye saturation setting. This mimics the relative intensity that would be seen on an analog oscilloscope.</p><p>Although you can generate only one eye diagram per decoder, up-to-four decoders of the same (or different) sources can be activated at once, enabling you to generate and display multiple eye diagrams. Figure 1 above shows three active decoders, including two eye diagrams generated from USB4 Gen3 decodes and a USB4-SB (sideband) decode. </p><h3 style="text-align: left;">Eye Mask Testing</h3><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_vlBHnVU0tCpoc2Csm_xzMNZEPUu_bwHUQ7HBzb9jp-1Wq6rBeGtuZH_Md_NXo8n6Ntso-UoyCqmWJgkI-q65x16e6SCoa9wGM-eyA615GH3Ks_iwh2GyiXrAea0U6hiahTEnefo1uHXXSqq4xM_IjzJVzUM5vq45hZH2RMeW8CV81VlNvhgsyDpX4A/s1920/USBEye_Pt1Fig4.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Eye diagram mask test" border="0" data-original-height="1027" data-original-width="1920" height="171" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_vlBHnVU0tCpoc2Csm_xzMNZEPUu_bwHUQ7HBzb9jp-1Wq6rBeGtuZH_Md_NXo8n6Ntso-UoyCqmWJgkI-q65x16e6SCoa9wGM-eyA615GH3Ks_iwh2GyiXrAea0U6hiahTEnefo1uHXXSqq4xM_IjzJVzUM5vq45hZH2RMeW8CV81VlNvhgsyDpX4A/w320-h171/USBEye_Pt1Fig4.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. The eye diagram for a USB-PD decode <br />showing a mask test. Mask violations, or ‘hits’,<br />are marked with red circles. </span></td></tr></tbody></table>Basic eye mask testing is available, showing the number and placement of eye hits. Standard masks for most protocols are included, or you can upload and use your custom mask files. Mask testing gives you an immediate, visual indicator of whether the signal is compliant with the standard. Figure 3 shows an eye diagram generated from a USB-PD decode with an eye mask test.<h3 style="text-align: left;"></h3><h3 style="text-align: left;">Eye Diagram Measurements</h3><p class="MsoNormal"><o:p></o:p></p><div>Several standard eye diagram measurement parameters provide
a way of quantifying the eye opening. The two foremost measurements, included with all "ME" decoders, are Eye
Height and Eye Width. <div><p><b>Eye Height</b> is a measurement of the minimum vertical eye opening; basically, a determination of the signal to noise ratio. The measurement is made by taking the difference of the means of the one and zero levels then subtracting three times the standard deviation of each level. </p><p><b>Eye Width</b> gives an indication of the total horizontal jitter in the signal. Like the Eye Height, the measurement is statistical in nature. The horizontal histograms of two adjacent crossing points are used to determine the mean and standard deviations of crossing times. Three times the standard deviation of each distribution is subtracted from the difference of the two mean values.</p><p class="MsoNormal">For multi-level PAM signals, these measurements can be applied to any eye individually.</p><h3 style="text-align: left;">Filtering Eye Diagrams and Eye Measurements<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCdaVBhJLJk_B4SAfS1FoUk7mnnsfDgIWr9MOvYZEqEDLGS4EnDZsFGSfnxBcyWMa1QdZsvwrZhN05gabajxff_MaNOzjNlT16yTPX1Ws2r04dnrhPxZTUmFOxlAWS28VV_2ERtCwajjd79ngbnJxQHMnS3LZC0iHgZevPhErhcLFHEp334XpispJ6rw/s1242/USBEye_Pt1Fig3.png" style="margin-left: auto; margin-right: auto;"><img alt="Eye diagram parameters" border="0" data-original-height="644" data-original-width="1242" height="332" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCdaVBhJLJk_B4SAfS1FoUk7mnnsfDgIWr9MOvYZEqEDLGS4EnDZsFGSfnxBcyWMa1QdZsvwrZhN05gabajxff_MaNOzjNlT16yTPX1Ws2r04dnrhPxZTUmFOxlAWS28VV_2ERtCwajjd79ngbnJxQHMnS3LZC0iHgZevPhErhcLFHEp334XpispJ6rw/w640-h332/USBEye_Pt1Fig3.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. Eye Height and Eye Width are the foremost parameters used to measure the eye opening, assuring that logical 1 and 0 can be easily discerned.</span></td></tr></tbody></table></h3><p class="MsoNormal"><o:p></o:p></p><p>All Teledyne LeCroy decoder software features an interactive
table of decoder results. Individual columns of this table can be filtered to
show only results from a particular device ID or containing a particular data value. </p><p>Because the eye is based on a decoding of the packetized signal, when the table is filtered, the eye diagrams are regenerated from only those UIs that match the filter criteria, enabling you to immediately see the signal integrity associated with particular types of packets. Any eye measurements that have been applied to the eye are also recalculated to show the results for only those UIs.</p><p>The "Apply to Zoom" feature also can be used to redraw the eye and recalculate eye measurements using only those UIs that are included in region of the source zoom. Simply touch a row of the table to "zoom" to that packet, and immediately you will see the eye and measurement results for only the highlighted area of the table representing the selected packet.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-vocCJNuxulJ1n7D8nuu5keAwP9TyeQkKxMp6IvWlC1d4LLAyWq1jypoIYBQ3dZiVKkLNYqfWK_StBKfWf5ot-Txzd7YWemgR3I0VHYClK3lJ973yILcPNS8BNvBKM_EMTSrp_5z-7grfEFbnJVsVD5ZXwDhwjsnrS0kLOT-jfZPmo4fIJKGDSpu_vw/s2920/MECompEyes.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="661" data-original-width="2920" height="144" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-vocCJNuxulJ1n7D8nuu5keAwP9TyeQkKxMp6IvWlC1d4LLAyWq1jypoIYBQ3dZiVKkLNYqfWK_StBKfWf5ot-Txzd7YWemgR3I0VHYClK3lJ973yILcPNS8BNvBKM_EMTSrp_5z-7grfEFbnJVsVD5ZXwDhwjsnrS0kLOT-jfZPmo4fIJKGDSpu_vw/w640-h144/MECompEyes.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 5. "Apply to Zoom" redraws the eye and recalculates measurements as <br />different packets within the same acquisition are selected from the table.</td></tr></tbody></table><h3>Serial Decoders with Physical Layer Tests</h3><p></p><p>Serial decoders sold with “M<b>P</b>”—<b>M</b>easure/Graph and <b>P</b>hysical Layer Test—capability feature more robust eye diagramming and measurements designed to meet the specifications of the PHY tests prescribed by the standard. You will have many more eye measurements and options for how the eye is generated. For example, in some cases, the eye can be generated as seen at either the transmitter or receiver, but as with the “ME” options, only one eye can be generated at once per decoder. </p><p class="MsoNormal">Although no serial decoder can measure eye diagrams with sufficient
rigor for compliance testing (our <a href="https://teledynelecroy.com/options/default.aspx?categoryid=12&groupid=140&capid=102&mid=506" target="_blank"><u>QualiPHY® (QPHY) </u>products</a> do that), they are
an excellent pre-compliance test of signal integrity, and viewed alongside the decoding make quick work of debugging signal integrity
problems.<o:p></o:p></p><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2022/10/oscilloscope-testing-of-10base-t1s.html" target="_blank">Oscilloscope Testing of 10Base-T1S Automotive Ethernet Signal Integrity</a></div><div><br /></div><div><a href="https://blog.teledynelecroy.com/2021/03/tdme-primer-serial-trigger-and-sequence.html" target="_blank">TDME Primer: Serial Trigger and Sequence Mode Sampling</a></div><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2021/03/tdme-primer-selecting-sample-rate-for.html" target="_blank">TDME Primer: Selecting Sample Rate for Serial Bus Analysis</a></p><p><br /></p><p><br /></p><p><br /></p><p><br /></p><p><br /></p><p><br /></p><p><br /></p></div></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-11004302507808957912022-10-10T08:00:00.119-04:002022-10-10T08:00:00.182-04:00Oscilloscope Testing of 10Base-T1S Automotive Ethernet Signal Integrity<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipjLxUKtPARNsVM2B9-hWnLQnahZbhLrYrTDzZ_PSTVls5iW_zyvAE_vtMSBCtJF30kTb60WUwd2-mPK0Bgnm8LIcrEIphXXIKxusQVb18Gqyj2Xaqv1-tLE0YZPKuk4yox2xdtC8t0qjDq5pEwPD-2iDKGsd5lJR8VAXFfftvjkvck0_5U_aTEkKFVw/s1920/10BaseT1S%20Fig5.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Eye diagram generated from decoded 10Base-T1S signal" border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipjLxUKtPARNsVM2B9-hWnLQnahZbhLrYrTDzZ_PSTVls5iW_zyvAE_vtMSBCtJF30kTb60WUwd2-mPK0Bgnm8LIcrEIphXXIKxusQVb18Gqyj2Xaqv1-tLE0YZPKuk4yox2xdtC8t0qjDq5pEwPD-2iDKGsd5lJR8VAXFfftvjkvck0_5U_aTEkKFVw/w400-h225/10BaseT1S%20Fig5.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. The 10Base-T1S TDME option features <br />easy eye diagram creation for signal integrity analysis.<br />Click on any image to enlarge it.</span></td></tr></tbody></table>In addition to special serial data bus measurements of 10Base-T1S signals, the <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=681&groupid=88" target="_blank">10Base-T1S Trigger, Decode, Measure/Graph & Eye Diagram</a> (TDME) option automates the generation and display of eye diagrams on Teledyne LeCroy oscilloscopes. Eye diagrams are an important element of serial data analysis, used to understand the signal integrity of the communications network. <p></p><p>The eye diagram is a general-purpose tool for analyzing serial digital communications signals. It shows the effects of additive vertical noise, horizontal jitter, duty cycle distortion, inter-symbol interference, and crosstalk on a serial data stream. </p><p>The eye diagram is formed by overlaying repetitive occurrences of slightly more than a single clock period (UI) of a serial data signal on a persistence display which shows the accumulated history of multiple acquisitions, as shown in Figure 1.</p><p>Due to the use of Differential Manchester encoding (DME), the 10Base-T1S eye is formed with twice the signal clock rate. The signal shown has a symbol rate of 12.5 Mbps and the eye is clocked at 25 Mbps. <span></span></p><a name='more'></a><p></p><p>DME is a bipolar encoding scheme where a logical one is represented by transition (of either polarity) in the middle of a bit period. A logical zero is represented by the absence of a transition during the middle of a bit period. DME encoding is illustrated in Figure 2.</p><p></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii7RUizYzEJ7cXslh3rxkHG58Wrxyw3pACW4xyydiTrMGgx-hvGy6koy4A0dwKA0YgdRSne9b77VM_eu_61xMGDSOCmMgdQbijAZrOKT5AOxnqJQMC5pAQ5cA1J0CteaiYnFu_OiUbVU19jJxCmgD06ln5UijkmTy0grE4GDBaeiPgdXJJ9-KfYWuVmQ/s872/10BaseT1S%20Fig6.png" style="margin-left: auto; margin-right: auto;"><img alt="Bit transitions in a Differential Manchester (DME) data stream" border="0" data-original-height="148" data-original-width="872" height="108" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii7RUizYzEJ7cXslh3rxkHG58Wrxyw3pACW4xyydiTrMGgx-hvGy6koy4A0dwKA0YgdRSne9b77VM_eu_61xMGDSOCmMgdQbijAZrOKT5AOxnqJQMC5pAQ5cA1J0CteaiYnFu_OiUbVU19jJxCmgD06ln5UijkmTy0grE4GDBaeiPgdXJJ9-KfYWuVmQ/w640-h108/10BaseT1S%20Fig6.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. Differential Manchester (DME) encoding used in 10Base-T1S.</span></td></tr></tbody></table><p></p><p>DME uses a transition of either polarity during the middle of a bit period to indicate a logical 1 and the lack of a transition to signal a logical 0. The vertical blue dotted lines indicate the bit periods. The logical 1 signals break the bit period in half, so evaluating the eye requires the double symbol rate.</p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMyCIWSiEu-Df0MvE8Z8N3F4KRTue7GeU6thTRdMEgMOaxMu1xBBv6McakR3g6_zrFe94lIcir4c2ZIhjpUqaDBtgUFuZIlglxUU2E3qvCf1FX2jocbaSkwNhIKOOk4akeDkjVmoHFiJKDWQT9MnsH5aoQlq-p9SdEvSJyiRGvmhjXQyqTJW6c_GYXAw/s1920/10BaseT1S%20Fig7.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Significant eye measurements marked on a 10Base-T1S eye diagram" border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMyCIWSiEu-Df0MvE8Z8N3F4KRTue7GeU6thTRdMEgMOaxMu1xBBv6McakR3g6_zrFe94lIcir4c2ZIhjpUqaDBtgUFuZIlglxUU2E3qvCf1FX2jocbaSkwNhIKOOk4akeDkjVmoHFiJKDWQT9MnsH5aoQlq-p9SdEvSJyiRGvmhjXQyqTJW6c_GYXAw/w400-h225/10BaseT1S%20Fig7.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. An annotated view of the 10Base-T1S<br />eye diagram showing the significant eye parameters.</span></td></tr></tbody></table><p>Based on this information we can take a closer look at the 10Base-T1S eye diagram shown in Figure 3.</p><p>The bit period is 40 ns corresponding to the bit rate of 25 Mbps. This is the effective symbol rate for the DME signal. The data source for the eye diagram can be user selected to be the entire acquisition or a zoom of a selected data packet. </p><p>There are several measurement parameters that help characterize eye diagrams:</p><p><b>Zero Level</b> - The mean value of the logical 0 level of the eye diagram.</p><p><b>One Level</b> - The mean value of the logical 1 level of the eye diagram. </p><p><b>Bit Period</b> - The reciprocal of the effective symbol rate.</p><p><b>Eye Amplitude</b> - A measure of the overall amplitude of the eye. It is based on the difference between the simple mean of the one level and the simple mean of the zero level. It is generally measured near the center of the eye.</p><p><b>Eye Height</b> - This is a measurement of the minimum vertical eye opening; basically, a determination of the signal to noise ratio. The measurement is made by taking the difference of the means of the one and zero levels then subtracting three times the standard deviation of each level.</p><p><b>Eye Width</b> - The eye width gives an indication of the total horizontal jitter in the signal. Like the eye height the measurement is statistical in nature. The horizontal histograms of two adjacent crossing points are used to determine the mean and standard deviations of crossing times. Three times the standard deviation of each distribution is subtracted from the difference of the two mean values.</p><p>When enabled for the 10Base-T1S eye diagram, the eye height and eye width are displayed immediately below the eye diagram. </p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrEsqOab3oG12Fm6JOWtmuPgefdmfr7Iun9nlbv8PAlWpEkPixRjXmDBMhjN53DV0LcpSNQHAI569IYOVX2wq9Gp8KLiun9-rCdne_NvwReNrm1JqiCX2PH7JcWFOLn3Mm_eQdmpIOtaTWiXCwsnXrtJnFNUCbLcjArJ8zdntNmlf7EQkdgNnq_9VQ7w/s1920/10BaseT1S%20Fig8.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Overshoot and droop marked on a 10Base-T1S eye diagram" border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrEsqOab3oG12Fm6JOWtmuPgefdmfr7Iun9nlbv8PAlWpEkPixRjXmDBMhjN53DV0LcpSNQHAI569IYOVX2wq9Gp8KLiun9-rCdne_NvwReNrm1JqiCX2PH7JcWFOLn3Mm_eQdmpIOtaTWiXCwsnXrtJnFNUCbLcjArJ8zdntNmlf7EQkdgNnq_9VQ7w/w400-h225/10BaseT1S%20Fig8.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. Two vertical effects on the eye. The first pulse in the<br />packet SSD field has noticeable vertical overshoot and droop, <br />and Node ID #0 and ID #3 have differing zero levels. </span></td></tr></tbody></table><p>The vertical opening of the eye is affected by vertical related elements like additive noise and cross talk and other interfering signals as well as gain differences between devices on the bus. As an example of these vertical effects, consider the eye diagram of a 10Base-T1S packet shown in Figure 4.</p><p>This eye diagram is using color persistence where the more frequent occurrences appear in the brighter colors. The violet trace (samples with a low occurrence rate) at the top has a high one level related to the first bit in the SSD field of Node ID #3. It is a zero and so appears as a double width segment. </p><p>The other thing to notice is that the zero levels of the two nodes on the bus do not match exactly. The node with ID #0 has a higher zero level, which has the effect of decreasing the eye height. The measured eye height of 932 mV and eye width of 39.35 ns includes data from both nodes.</p><p>The eye diagram shown is based on the full acquired signal and sees both nodes on the bus. The user can elect to generate the eye diagram for only the displayed zoom trace associated with the selected packet in the decode table, rather than the full acquisition. In this way, the source of any aberrations noted in the full acquisition can be isolated, first by selecting a specific packet, then shifting the zoom trace horizontally until the aberration disappears.</p><p>The horizontal closure of the eye is the result of timing uncertainty. Timing jitter whether random, periodic or inter-symbol interference will tend to close the eye horizontally. Both nodes have common timing with no apparent horizontal differences.</p><h4 style="text-align: left;">Also see:</h4><p><a href="https://blog.teledynelecroy.com/2022/10/oscilloscope-measurements-of-10base-t1s.html" target="_blank">Oscilloscope Measurements of 10Base-T1S Automotive Ethernet PLCA Cycle Timing</a></p><p><a href="https://blog.teledynelecroy.com/2022/08/physical-layer-collision-avoidance-in.html" target="_blank">Physical-Layer Collision Avoidance in 10Base-T1S Automotive Ethernet</a></p><div><div><a href="https://blog.teledynelecroy.com/2022/08/10base-t1s-automotive-ethernet-vs.html" target="_blank">10Base-T1S Automotive Ethernet vs. 10Base-T1L Industrial Ethernet</a></div></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-86998512860170166502022-10-05T12:00:00.045-04:002022-10-05T12:00:00.171-04:00Oscilloscope Measurements of 10Base-T1S Automotive Ethernet PLCA Cycle Timing<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkUl62A-If-l-h-dsc6eEX5HNxazqw8JcPMeI16ABsBuHwjq2kAMtO8VOazISOhH8-vur2yUvR_B4aU_NMqA7oXu-_SLcYan_KRw1IHTK_DmiEMZFKOVMfgEzlITuHn6hKvxTM2AhhhQ-5Ed04SihtKsFcASk9n8bp7WF8awNqhnSjYTZJ9KJQvS8QsA/s1204/10BaseT1S%20Fig1.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="10Base-T1S frame with color-coded decoder overlay" border="0" data-original-height="485" data-original-width="1204" height="161" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkUl62A-If-l-h-dsc6eEX5HNxazqw8JcPMeI16ABsBuHwjq2kAMtO8VOazISOhH8-vur2yUvR_B4aU_NMqA7oXu-_SLcYan_KRw1IHTK_DmiEMZFKOVMfgEzlITuHn6hKvxTM2AhhhQ-5Ed04SihtKsFcASk9n8bp7WF8awNqhnSjYTZJ9KJQvS8QsA/w400-h161/10BaseT1S%20Fig1.PNG" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1. Color-coded decoding of 10Base-T1S<br />stream makes it easy to measure timing between<br />signal elements. Click on any image to enlarge.</td></tr></tbody></table>The <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=680&groupid=88" target="_blank">10Base-T1S Trigger-Decode</a> (TD) and <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=681&groupid=88" target="_blank">10Base-T1S Trigger, Decode, Measure/Graph & Eye Diagram</a> (TDME) options enable Teledyne LeCroy oscilloscope users to trigger on and decode Ethernet control and payload data from 10Base-T1S Automotive Ethernet signals. The decoding is color-coded to provide fast, intuitive understanding of the relationship between message frames and other time-synchronous events. Knowing the location of the various protocol elements makes it easy to measure Physical Layer Collision Avoidance (PLCA) cycle timing using either standard oscilloscope tools, or special serial bus measurements included with the TDME options.<p></p><p>PLCA cycle timing is measured to assure interoperability of the attached nodes in a 10Base-T1S mixed-segment, multidrop bus. This class of tests measures the timing between events on the bus relative to a specific bus event, usually the BEACON signal initiated by the Master node. </p><p>Let’s look at a simple example of a 10Base-T1S network with two nodes, the Master (Node 0) and a device (Node 3). The acquired waveform is shown in Figure 2, decoded using the 10Base-T1S TDME option. The top grid shows the complete acquisition, which consists mostly of BEACON signals over a record of twenty-five million samples. Toward the end of the acquisition are two packets from the other nodes. The table at the bottom of the screen lists all the elements decoded in the full acquisition.<span></span></p><a name='more'></a><p></p><h3 style="text-align: left;">Measuring BEACON Duration<br /><br /></h3><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsiYZtkW-HCrxwrAFOuhnLhTtBGduPBzeMCimQZeddacQpB3Y-mty0hOoborsscrlzDsp0ROlT3qKkcoxA4b01H8lV_b13JrB0I6V76Fq7YMBBqPByEyxpSSwbHVLeiFRSsNVcaL9aG-lZ9RHxfzAOcvUV7SQr4kn-JzHrg-FiYGI5KGL-BaXnFkligA/s1920/10BaseT1S%20Fig2.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Cursors placed on zoom of 10Base-T1S frame decoding to measure BEACON duration." border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsiYZtkW-HCrxwrAFOuhnLhTtBGduPBzeMCimQZeddacQpB3Y-mty0hOoborsscrlzDsp0ROlT3qKkcoxA4b01H8lV_b13JrB0I6V76Fq7YMBBqPByEyxpSSwbHVLeiFRSsNVcaL9aG-lZ9RHxfzAOcvUV7SQr4kn-JzHrg-FiYGI5KGL-BaXnFkligA/w400-h225/10BaseT1S%20Fig2.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 2. Cursors on zooms precisely measure<br />duration of BEACON signal.</td></tr></tbody></table>Once the desired entry is located in the table, clicking on that row will bring up a horizontally expanded zoom trace showing the selected entry in detail. In Figure 2, the packet from the Node ID # 3 is selected and expanded in zoom trace Z1, the second grid from top, making it easier to read the decoding. The duration of the BEACON signal can be estimated by using the Time column of the table, which reports the time at the beginning of the decoded element. Taking the difference between the start of the BEACON and the start of the following Silence, the duration of the BEACON is 2.1 µs. <p>Horizontal relative cursors can also be used to measure timing on the decoded signal with better precision. A good way to assure the best accuracy in a cursor measurement is to first zoom the trace being measured. Cursors are initially placed about the BEACON signal on the decode trace Z1 using either the front panel Cursor button or the Cursor drop-down menu. Then, further zooming the Z1 trace into Z3 allows the cursors to be moved and placed with much greater accuracy at the beginning and end of the BEACON. Ideally, the cursors should be placed at the logic switching threshold. The cursor time readout appears in the lower right corner of the screen under the timebase annotation box, reading 2.0820 µs. This is consistent with the 10Base-T1S specification that the BEACON duration be 20 clock cycles. At 10 MHz, this works out to 2 µs.</p><h3 style="text-align: left;">Measuring BEACON to Packet Timing<br /><br /></h3><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuuk-OIwbAPzW2iB7v94Rt-0nf-k2GeaCQmL_FqyihTwjmGC2P54uoSzUusk1AnMDQi4LjpYjVvv6Opevg5j9pLHlVv5Rapeg_W398xt6-3-zhvlflYg8WIEx42gtBvyGOCk2mcdnejooJectz4C7qzT8pIVcUsJThG-0V4xyIWVbJ_VDej90cpAXHAg/s1920/10BaseT1S%20Fig3.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Cursors placed on zooms of 10Base-T1S frame decoding to measure time from BEACON to data packet." border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuuk-OIwbAPzW2iB7v94Rt-0nf-k2GeaCQmL_FqyihTwjmGC2P54uoSzUusk1AnMDQi4LjpYjVvv6Opevg5j9pLHlVv5Rapeg_W398xt6-3-zhvlflYg8WIEx42gtBvyGOCk2mcdnejooJectz4C7qzT8pIVcUsJThG-0V4xyIWVbJ_VDej90cpAXHAg/w400-h225/10BaseT1S%20Fig3.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. Cursors on two zooms used to measure<br />time delay from end of BEACON to start of packet.</span></td></tr></tbody></table>A more commonly required measurement is the time from the end of the BEACON to the beginning of a packet sent by a node. This represents the time latency to the Transmit Opportunity (TO) for the node, in our example Node ID# 3. Figure 3 shows the measurement setup.<p>The Time column of the table can be used to estimate the delay from the end of the BEACON to the beginning of the Node 3 packet. This is the difference between the start of the Silence that follows the BEACON and the Start of Stream Delimiter (SSD). The Silence begins at -84.2 µs and the SSD begins at -72.91 µs, a difference of 11.29 µs. </p><p>The cursors can be used as before, only this time, due to the length of the packet, two zooms are used to see both the end of the BEACON (Z3) and the beginning of the packet (Z4) with sufficient resolution to place cursors accurately. The significant measurement points on the zoom traces are aligned with the measurement points on zoom trace Z1. The measured time difference is 11.2128 µs.</p><p>Time differences between any fields of the decoded signal can be measured with cursors in this manner. </p><h3 style="text-align: left;">Measuring Time Between BEACONs<br /><br /></h3><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0My4PFEcEBVVCiK7Cd6z6OQyi4fq8vsEtvOLvd9pZ0oX-M_IZCxWg6ztMvVwhFC-DK9tZcD9qZnni91yJHQ-sy9r2YAHh5gjT0-DeZ88_7BBwVGdPfZvdBtBirNlSOj7MDVcLFYzXREcsvwHGKp30poPZQFCeUJ3LmANSU-h1kafXOINTD0EwlqezvQ/s1920/10BaseT1S%20Fig4.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Filtering 10Base-T1S decoder result table to show only BEACONS." border="0" data-original-height="1082" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0My4PFEcEBVVCiK7Cd6z6OQyi4fq8vsEtvOLvd9pZ0oX-M_IZCxWg6ztMvVwhFC-DK9tZcD9qZnni91yJHQ-sy9r2YAHh5gjT0-DeZ88_7BBwVGdPfZvdBtBirNlSOj7MDVcLFYzXREcsvwHGKp30poPZQFCeUJ3LmANSU-h1kafXOINTD0EwlqezvQ/w400-h225/10BaseT1S%20Fig4.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. Applying filters and serial bus measurement<br />parameters to measure time between BEACONs. </span></td></tr></tbody></table>The 10Base-T1S TDME option includes 10 serial bus measurement parameters that can be applied to decoded serial data streams. Of particular interest for 10Base-T1S is the Delta Message parameter, which can be used to measure time between BEACONs. To do this, first filter the decoder table to show only Type BEACON by clicking the down-arrow symbol in the Type column header, then entering your filter criteria (e.g., Contains BEACON).<p></p><p>Once the table is filtered, open the Measure/Graph tab and set up the Delta Message parameter, using the active Decode <i>N</i> as the source. In Figure 4, the time measured between BEACON transmissions is a minimum of 1.2608 ms, maximum of 1.3228 ms, and mean value of 1.28738 ms. </p><p>The TDME Measure/Graph tab also allows you to optionally graph measurement results as a track, trend, or histogram. In this example the track function is selected and routed to math trace F1. Each measured delay value is plotted time synchronously with the acquisition in the F1 math trace. </p><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2022/08/physical-layer-collision-avoidance-in.html" target="_blank">Physical-Layer Collision Avoidance in 10Base-T1S Automotive Ethernet</a></div><div><br /></div><div><a href="https://blog.teledynelecroy.com/2022/08/10base-t1s-automotive-ethernet-vs.html" target="_blank">10Base-T1S Automotive Ethernet vs. 10Base-T1L Industrial Ethernet</a></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-41839600286888299332022-09-12T08:00:00.295-04:002022-09-12T08:00:00.159-04:00Isolated Oscilloscope Inputs vs. Isolated Oscilloscope Probes<p><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">Some users in high-voltage test environments seek measuring instruments with isolated inputs because they want the safety and convenience of isolation without having to spend money on an isolated oscilloscope probe, like the Teledyne LeCroy </span></span><a href="https://teledynelecroy.com/probes/power-probes.aspx#dl-iso" style="font-family: Calibri, sans-serif; font-size: 14.6667px;" target="_blank">DL-ISO</a><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;"> or the Tektronix IsoVu®. While that's understandable, isolated inputs built into the instrument channel may be convenient, but they don't necessarily give you good performance, certainly not as good as you would get from a high quality, high-voltage isolated probe.</span></span></p><p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsOphj58NFVwcuP7uEbeGzys12DAxrH0wZh-zdvPeNtvcasHx8RsWbDFfnHpxvf9nIr_AbPF-QIOIhxCG6VsXe7pyKqYzyk4l4URt7yfgC6G0wEIQTG_SoEzDPNdFUCgwTrQl6m13fBaW_-8UkyGDOqAxqciSh6FOv4UHVwPuU-BquqJBKliyMkhlG3Q/s1039/DL850vHVFO.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="511" data-original-width="1039" height="314" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsOphj58NFVwcuP7uEbeGzys12DAxrH0wZh-zdvPeNtvcasHx8RsWbDFfnHpxvf9nIr_AbPF-QIOIhxCG6VsXe7pyKqYzyk4l4URt7yfgC6G0wEIQTG_SoEzDPNdFUCgwTrQl6m13fBaW_-8UkyGDOqAxqciSh6FOv4UHVwPuU-BquqJBKliyMkhlG3Q/w640-h314/DL850vHVFO.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1. Cascaded H-bridge signals captured using an isolated input (left) and an isolated probe (right).</td></tr></tbody></table></p>
<p class="MsoNormal" style="margin-top: 4.0pt;"><span style="color: black; font-family: "Calibri",sans-serif; font-size: 11.0pt; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: Calibri;"><span></span></span></p><a name='more'></a><p></p><p class="MsoNormal" style="margin-top: 4.0pt;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">Isolated inputs often utilize very long, highly capacitive unshielded cable connections to the instrument, which is never good in a high-voltage environment where you have fast transients</span></span><span style="font-family: Calibri, sans-serif; font-size: 14.6667px;">—</span><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">it's just an EMI nightmare. A coaxial cable is going to provide some protection against transients, and probes by and large use a coaxial connection to get from the probe head, or the amplifier, back to the oscilloscope, so they're a bit more protected against EMI by design than something that's using a very cheap wire assembly to get to an isolated input.</span></span></p><p class="MsoNormal" style="margin-top: 4.0pt;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">Let's compare signals measured on a 1 GHz Teledyne LeCroy </span></span><a href="https://teledynelecroy.com/oscilloscope/hdo6000.aspx" style="font-family: Calibri, sans-serif; font-size: 14.6667px;" target="_blank">HDO6000</a><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;"> 12-bit high resolution oscilloscope using our first generation fiber-optic isolated probe </span></span><span style="font-family: Calibri, sans-serif; font-size: 14.6667px;">(</span><a href="https://teledynelecroy.com/probes/high-voltage-optically-isolated-probes" style="font-family: Calibri, sans-serif; font-size: 14.6667px;" target="_blank">HVFO108</a><span style="font-family: Calibri, sans-serif; font-size: 14.6667px;">)</span><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;"> to the same signals measured on a 12-bit Yokogawa DL850 Scopecorder using a 10:1 passive probe to the isolated BNC input. We've lowered the oscilloscope bandwidth and sample rate to be comparable to the Scopecorder, and adjusted the oscilloscope grid to be about the same aspect ratio as the Scopecorder, so the comparison is as close to one-to-one as we can make it. </span></span></p><p class="MsoNormal" style="margin-top: 4.0pt;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">The waveforms are captured from a cascaded H-bridge using Silicon devices, so the rise times are not especially fast, well within the 20 MHz bandwidth range of the Scopecorder. It's an approximately 400 Vdc bus. If you look on the lower right, you'll see that the sample rate of the Teledyne LeCroy oscilloscope is 100 MS/s, which matches the Scopecorder on the left, and we've applied a 20 MHz bandwidth filter, so it's nominally a 20 MHz instrument, like the Scopecorder. One long acquisition with three different signals in it was taken on both instruments using the same vertical settings. The upper side gate-drive on the left is green and on the right it's yellow, due the different colors assigned to the input channels on the two instruments—that's the only difference.</span></span></p><p class="MsoNormal" style="margin-top: 4.0pt;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">The yellow signal captured with the fiber-optic isolated probe travels up, flattens out around the Miller plateau, then just rises to the top value. It looks pretty good. We see a large amount of ringing, though, on the green signal from the Scopecorder isolated input. To some extent, that's really just the nature of the high-capacitance assembly of the probe all the way back to the input. </span></span></p><p class="MsoNormal" style="margin-top: 4.0pt;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">The lower-side gate drive signal (magenta) is an especially good comparison, because we shouldn't have some of the issues we have with the upper-side gate drive, where we're using very different probe topologies. In both cases, we're using a passive probe for the lower-side gate drive measurement, so it really is almost a one-to-one comparison. However, on the Scopecorder, we still see some ringing. We can see the transient when the upper-side switches, it's picked up pretty well. The passive probe used for the Teledyne LeCroy oscilloscope is coaxial back to the input, which may not be the case with the Scopecorder capture on the left. You can still see the transient pickup from that upper-side switching, but it's quite limited compared to the isolated input side. </span></span></p><p class="MsoNormal" style="margin-top: 4.0pt;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">So, when you think, "Hey, wouldn't it be great if my 1 GHz oscilloscope had isolated inputs?" know that it's not the magic panacea you might wish. It may be safe. It's well-understood. It may be a great way to measure very low-bandwidth sensor signals, but it's not such a great way to measure things that are switching very fast and generating lots of fast transients. Your best bet is a high-quality isolated probe, like the </span></span><a href="https://teledynelecroy.com/probes/power-probes.aspx#dl-iso" style="font-family: Calibri, sans-serif; font-size: 11pt;" target="_blank">HVFO108 or the DL-ISO</a><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">.</span></span></p><p class="MsoNormal" style="margin-top: 4.0pt;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">To learn more, watch our on-demand webinars:</span></span></p><p class="MsoNormal" style="mso-margin-top-alt: auto;"><a href="https://go.teledynelecroy.com/high-voltage-probing-webinar?&utm_source=website&utm_medium=events-page&utm_campaign=22-05-17-probing-in-pwr-webinar-part-1&utm_content=on-demand" target="_blank"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">Power Electronics Probing</span></span><span style="font-family: Calibri, sans-serif; font-size: 14.6667px;">—</span><span style="font-family: Calibri, sans-serif; font-size: 14.6667px;">What to Use and Why, Part 1: How to Choose the Correct High-voltage Probe</span></a></p><p class="MsoNormal" style="mso-margin-top-alt: auto;"><a href="https://go.teledynelecroy.com/high-voltage-probing-examples?&utm_source=website&utm_medium=events-page&utm_campaign=22-06-08-probing-in-pwr-webinar-part-2&utm_content=on-demand" target="_blank"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">Power Electronics Probing</span></span><span style="font-family: Calibri, sans-serif; font-size: 14.6667px;">—</span><span style="font-family: Calibri, sans-serif; font-size: 14.6667px;">What to Use and Why, Part 2: Real World Examples and Comparisons</span></a></p><h4 style="text-align: left;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;">Also see:</span></span></h4><p class="MsoNormal" style="mso-margin-top-alt: auto;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;"><a href="https://blog.teledynelecroy.com/2022/09/choosing-high-voltage-oscilloscope.html" target="_blank">Choosing a High-voltage Oscilloscope Probe for SiC/GaN Power Semiconductor Device Measurements</a></span></span></p><p class="MsoNormal" style="mso-margin-top-alt: auto;"><span style="font-family: Calibri, sans-serif;"><span style="font-size: 14.6667px;"><a href="https://blog.teledynelecroy.com/2022/08/how-to-choose-best-high-voltage.html" target="_blank">How to Choose the Best High-voltage Oscilloscope Probe in 5 Minutes</a></span></span></p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-49026454634938396122022-09-05T08:00:00.157-04:002022-09-05T08:00:00.162-04:00Choosing a High-voltage Oscilloscope Probe for SiC/GaN Power Semiconductor Device Measurements<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDfvRCxbDWLuZea3FnASh-N2DAcTiwYx-xyv8NvNKG6QE-SYeq3L-1rFwoZp9sZuJd2mbz8JV8LvcQGGyei5Ed5XVqAI7a2CNBTVj0TK-CAW4yiJfO6KRvzZrPgO5XkfvxK-oPfazXE4x5cSrPYtn6gEp1-p87VejGyTpJ1sd6U1_MAyqAM9Wln4lfWw/s2560/RightHVProbe_Fig5.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Wide-bandgap (GaN) power semiconductor device waveforms captured using two, different probe topologies" border="0" data-original-height="1440" data-original-width="2560" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDfvRCxbDWLuZea3FnASh-N2DAcTiwYx-xyv8NvNKG6QE-SYeq3L-1rFwoZp9sZuJd2mbz8JV8LvcQGGyei5Ed5XVqAI7a2CNBTVj0TK-CAW4yiJfO6KRvzZrPgO5XkfvxK-oPfazXE4x5cSrPYtn6gEp1-p87VejGyTpJ1sd6U1_MAyqAM9Wln4lfWw/w400-h225/RightHVProbe_Fig5.png" title="GaN Power Semiconductor Device Waveforms" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1: Wide-bandgap (GaN) power semiconductor device<br />waveforms captured using two, different probe topologies.<br />Click on any image to expand.</span></td></tr></tbody></table>In our last post, we introduced you to a new tool on the Teledyne LeCroy website: <a href="https://teledynelecroy.com/powerprobes" target="_blank">The High-voltage Probe Selection Guide</a>. To demonstrate the benefits of the guide, let’s explore further what must be considered when choosing an HV oscilloscope probe for power semiconductor device measurements.<p></p><p>Why are power semiconductor device measurements challenging?<span></span></p><a name='more'></a><p></p><p></p><ul style="text-align: left;"><li>It is relatively easy to measure the lower side power semiconductor devices (MOSFET or IGBT) because they are referenced to ground. Single-ended passive probes can be used but are not recommended because it is easy to carelessly probe a high-voltage portion of the circuit and damage the probe, oscilloscope or the device under test, or cause harm to the operator.</li><li>It is harder to measure the upper side power semiconductor devices because they are referenced to a voltage that is non-zero. This is called a <i>floating </i>measurement. This precludes use of the ground-referenced single-ended probes, as they would short circuit the DUT. This measurement requires a high-voltage differential or single-ended isolated probe.</li><li>The upper side power semiconductor device measurements benefit from the high common-mode rejection ratio (CMMR) of an optically isolated probe, like the <a href="https://teledynelecroy.com/probes/high-voltage-optically-isolated-probes" target="_blank">DL-ISO</a> or Tektronix® IsoVu™, to help resist switching interference from the lower side devices. </li><li>When measuring wide-bandgap devices, such as Gallium-nitride (GaN) and Silicon-carbide (SiC), high bandwidth may also be desired to accommodate the faster rise times supported by these devices.</li></ul><p></p><p>Measuring both upper and lower power semiconductor devices simultaneously gives complete insight into the design’s behavior. In addition to evaluating the switching losses, designers will evaluate the timing to learn if there is sufficient dead-time margin to preclude any possibility of both upper and lower devices being turned on at the same time, which would cause a short circuit (shoot through). So, it's essential to have a probe that can perform adequately for the upper side measurements.</p><h3 style="text-align: left;">Choosing with the High-voltage Probe Selection Guide</h3><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJIS5RQbtZ49lTb9OIY6AVwX63RZXVxulocZ9wfFrRIKVWn5LYDRpmXf_ABef3stOsJWAuzue5Brhsa_mUidBFU1RpaLYHluMrQdzsqq2QloHjts4e18SOGVsqCepk1oxfsRDxc37g4Y6YmQq4dGcbl5_ZVg4QYcbO6Mmc1N7Ssq3uB9XGW2vtZL-C3A/s1035/RightHVProbe_Fig2.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Topology of a circuit using four wide-bandgap (GaN) MOSFETs." border="0" data-original-height="825" data-original-width="1035" height="254" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJIS5RQbtZ49lTb9OIY6AVwX63RZXVxulocZ9wfFrRIKVWn5LYDRpmXf_ABef3stOsJWAuzue5Brhsa_mUidBFU1RpaLYHluMrQdzsqq2QloHjts4e18SOGVsqCepk1oxfsRDxc37g4Y6YmQq4dGcbl5_ZVg4QYcbO6Mmc1N7Ssq3uB9XGW2vtZL-C3A/w320-h254/RightHVProbe_Fig2.png" title="Full-bridge Power Semiconductor Device Circuit" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2: Topology of a full-bridge <br />wide-bandgap (GaN) transistor.</span></td></tr></tbody></table>The circuit to be tested is a full-bridge topology using four wide- bandgap (GaN in this case) metal oxide semiconductor field effect transistors (MOSFETs). The desired measurement is to determine the switching losses of the MOSFETs. There are two lower side MOSFETs and two upper side MOSFETs, as shown in Figure 2.<p></p><p>Based on this information, we make three, simple selections on the High-voltage Probe Selection Guide (Figure 3): </p><p></p><ul style="text-align: left;"><li>DC Bus Voltage = 170 – 1000 Vdc</li><li>Semiconductor Device Material = Wide-bandgap (SiC or GaN)</li><li>Applications = Power Semiconductor Testing</li></ul><p></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgceREmHQUcUbVls-2evqezy470wWx_fr9JlxB5YJUwxC5e0CJ9mkO_8nZWOJeUgDQSPMC_t0-QgBPfiR0CR69NF1_5-ZJVee9VnAEz0y44PdsZyc-vM0GE4yyywD5AbaJhkW5zVcr6RbYxJmEvkwcf9at4cinjBjAmRlT9KKQeXD51pLxjC4Hu5mlJ_Q/s997/RightHVProbe_Fig3.png" style="margin-left: auto; margin-right: auto;"><img alt="High-voltage Probe Selection Guide selections for testing on a 260 Vdc bus wide bandgap (GaN) transistor." border="0" data-original-height="800" data-original-width="997" height="514" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgceREmHQUcUbVls-2evqezy470wWx_fr9JlxB5YJUwxC5e0CJ9mkO_8nZWOJeUgDQSPMC_t0-QgBPfiR0CR69NF1_5-ZJVee9VnAEz0y44PdsZyc-vM0GE4yyywD5AbaJhkW5zVcr6RbYxJmEvkwcf9at4cinjBjAmRlT9KKQeXD51pLxjC4Hu5mlJ_Q/w640-h514/RightHVProbe_Fig3.png" title="High-voltage Probe Selection Guide" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3: Selections for testing on a 260 Vdc bus wide bandgap (GaN) transistor.</span></td></tr></tbody></table><p>The Guide chooses the <a href="https://teledynelecroy.com/probes/high-voltage-optically-isolated-probes" target="_blank">DL-ISO Series High-Voltage Optically Isolated Probe</a> as the best probing option (green) for the gate drive and switching loss measurements. </p><p>The <a href="https://teledynelecroy.com/probes/high-voltage-differential-probes" target="_blank">HVD Series High-Voltage Differential Probe</a> is a better option than a single-ended passive probe, but it may cause circuit loading due to its input capacitance. It may also have insufficient bandwidth for the faster wide bandgap devices, especially the GaN device used in the example. There are compromises in using this type of probe, but some users may find that the probe works fine for their particular measurement needs. </p><p>One reason the DL-ISO is the best option is the probe’s CMRR. The DL-ISO series has a CMRR of 160 dB at DC and significantly higher CMRR than the other probes at higher frequencies. The HVD probe has a CMRR of 85 dB at DC and 65 dB at 1 MHz. While the HVD Series probe has excellent CMRR for a conventional HV differential probe, and may perform acceptably well depending on the device and the circuit, CMRR is not as good as DL-ISO, and it has much less than 1 GHz bandwidth.</p><p>Finally, the DL-ISO Series offers up to 1 GHz bandwidth to match the requirements of GaN devices. The HVD Series probes have a bandwidth of up to 400 MHz, corresponding more closely to the bandwidth requirements of SiC or Silicon (Si) power semiconductor devices.</p><p>The best choice for this type of power device measurement is the single-ended, fiber optically isolated probe. Its single-ended configuration minimizes loading, which offers the benefit of better signal fidelity. The probe isolation circuitry is less susceptible to picking up transients. It has better CMRR at high frequencies, which is important for circuits using wide bandgap semiconductors such as the GaN MOSFETs in this example. This, combined with the probe’s isolation circuitry, results in more accurate upper side measurements.</p><h3 style="text-align: left;">Real-world Capture Comparison</h3><p>To prove the point, let’s compare Vds (MOSFET Drain-Source) signals captured using a DL-ISO probe and an HVD probe (Figure 1). The DL-ISO probe (magenta trace) is connected to the gate of one of the upper side MOSFETs. The HVD probe (blue trace) is connected to the gate of the other upper side MOSFET. This allows simultaneous observation without the probes affecting each other by loading the circuit, which would happen if they were connected to the same measurement point. </p><p>Note that the HVD probe exhibits a small overshoot on the edge transitions. This overshoot is most probably due to the lower CMRR of the HVD probe compared to the DL-ISO. There is no discernible overshoot visible in the signal from the DL-ISO probe. The optical coupling of the DL-ISO probe provides the best CMRR performance, which helps to suppress electrical transients coming from elsewhere in the circuit.</p><p class="MsoNormal">To try the High-voltage Probe Selection Guide, visit: <a href="https://teledynelecroy.com/powerprobes">teledynelecroy.com/powerprobes</a><o:p></o:p></p><h4 style="text-align: left;">See also:</h4><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2022/08/how-to-choose-best-high-voltage-probe.html" target="_blank">How to Choose the Best High-voltage Probe in 5 Min.</a></p><p class="MsoNormal"><br /></p><p><br /></p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-86836263975897591442022-08-29T08:00:00.049-04:002022-08-29T08:00:00.165-04:00How to Choose the Best High-voltage Oscilloscope Probe in 5 Minutes<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9IgbyA4RcU3nGWIwe-KYoIaS6roPeev7cJhwkvqUranKByMBwM3pOAU4m8BEja9vZWy3nPCWUHHsfok-q539NDyhmBOOyYJ3Dtlt8ZRz-Nig8gwb0uWEy2fTX_YvmIwfw_TyHAxAUecbk7AtWEySy2TyPU6u-ilKMeT_EI8JoH48nAUI9JYGXF5G9Gw/s1596/RightHVProbe_Fig1.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="High-voltage Probe Selection Guide color codes better or worse probe selections." border="0" data-original-height="1330" data-original-width="1596" height="267" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9IgbyA4RcU3nGWIwe-KYoIaS6roPeev7cJhwkvqUranKByMBwM3pOAU4m8BEja9vZWy3nPCWUHHsfok-q539NDyhmBOOyYJ3Dtlt8ZRz-Nig8gwb0uWEy2fTX_YvmIwfw_TyHAxAUecbk7AtWEySy2TyPU6u-ilKMeT_EI8JoH48nAUI9JYGXF5G9Gw/w320-h267/RightHVProbe_Fig1.PNG" title="Teledyne LeCroy High-voltage Probe Selection Guide" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1: The High-voltage Probe Selection Guide <br />color codes better or worse probe selections based on<br />your answers to three, simple questions. <br />Click any image to enlarge.</span></td></tr></tbody></table>Probing high-voltage (HV) circuits for analysis with an oscilloscope presents unique challenges due to the potential for injury or equipment damage, as well as the demands of the materials used in HV semiconductors. HV floating measurements are extremely dangerous and difficult to make. Conventional passive probes are not the answer, but isolated and high-voltage differential probes are options. Yet, with many possible choices in these categories, how can you decide which is actually the best HV oscilloscope probe for <i>your </i>application?<p></p><p>Teledyne LeCroy offers this new, easy way to help you select a high-voltage oscilloscope probe based on your specific application—the High-voltage Probe Selection Guide—available on the Teledyne LeCroy website at: <a href="https://teledynelecroy.com/powerprobes">teledynelecroy.com/powerprobes</a><span></span></p><a name='more'></a><p></p><h3 style="text-align: left;">The Three, Most Basic Questions</h3><p>When you go to the High-voltage Probe Selection Guide, you will be asked three, basic questions that determine the rightness or wrongness of any probe for a given application.</p><h4 style="text-align: left;">What Is the DC Bus Voltage?</h4><p>The DC bus voltage will determine the maximum voltage rating required for the probe to be used in the measurement. For AC line signals, this is the peak-to-peak voltage of the AC line. In a switched mode power device, the bus voltage is most often either the full wave rectified peak voltage AC line or the amplitude of the pulse width modulated (PWM) signals from the driver/inverter circuits.</p><h4 style="text-align: left;">What Is the Semiconductor Device Material?</h4><p>Silicon (Si), Silicon Carbide (SiC) and Gallium Nitride (GaN) are all popular materials for semiconductor devices, each with its unique requirement on rise times for the switching signals:</p><p></p><ul style="text-align: left;"><li>Si devices typically cannot handle rise times faster 10 ns</li><li>Rise times on SiC devices are 3 to 5 ns or slower </li><li>Rise times on GaN devices are on the order of 1 to 3 ns </li></ul><p></p><p>The larger the voltage swing, the slower the rise times get to help keep EMI in check.</p><p>To measure fast rise times, as well as some harmonics, the probe needs to have sufficient bandwidth. For example, to measure gate drive signals on a GaN device, the probe bandwidth required might be closer to 1 GHz, whereas to measure output signals on the same GaN device, the bandwidth required could be 700 MHz or even as low as 350 MHz. </p><h4 style="text-align: left;">What Are the Applications?</h4><p>The High-voltage Probe Selection Guide asks you the intended measurement application, offering a choice of power semiconductor test, floating sensor or system inputs /outputs measurements. This high-level categorization determines the relative importance of many possible probe specifications, including the voltage range, bandwidth, attenuation and isolation. </p><p>Power semiconductor testing refers to measurements made on individual devices. This includes capturing MOSFET/IGBT gate drive and output signals, then analyzing them. Analysis includes dead time verification and switching loss measurements. Depending on which semiconductor device is being tested, ideal probe features could include wide voltage range, offset capability, very good CMRR and higher bandwidth. </p><p>Floating sensor measurements include probing series or shunt resistors, current or temperature sensors, or discrete components. This type of application usually determines the isolation requirements of the probe, as the signals involved are generally small with large voltage offsets.</p><p>System input/output measurements include the line-side AC voltage, DC/DC converter high- or low-voltage inputs or outputs, DC bus or link, and inverter drive PWM outputs. Wide voltage range and common mode are typical features associated with probes for this application.</p><h3 style="text-align: left;">Using the High-voltage Probe Selection Guide</h3><p>Open the High-voltage Probe Selection Guide, answer the three basic questions, and you will get a recommendation for a high-voltage probe with notes on our reasoning behind the choice. </p><p>The selection guide rates the appropriateness of each probe using a simple, color-coded scheme:</p><p><b>Black:</b> The probe should absolutely not be used for this application, as damage to the probe, oscilloscope or device under test (DUT) may occur, or harm may come to the operator. </p><p><b>Red: </b>The probe may be safe to use for this application, but it will probably not provide a good measurement result.</p><p><b>Yellow:</b> There are some compromises in performance of the probe in this application, though some users may find the probe works fine for them.</p><p><b>Green: </b>This is the perfect probe. There are few issues with its use, and it has been optimized in price and performance for the application. Sometimes, it may be the only safe choice.</p><p>The principal reason for the code is shown right on the screen, with more more information behind the "i" button.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIdoUUXosnKFwbYePSo4cLpyRFDIUB5rVbRYFILjPloXcL6btdAKKO3uRN8zhmWz1q8CrwS4F5gl23VTTdt5q0uj3aNUo7XPe4nkHQiYfOzyVjrZvv6WZ4J8x8x1Ah750QzuEsT97uMJfXDXmm-aBT938fYNu-z8OcKpJ2h616_JuAjlcC11OAq305gg/s997/RightHVProbe_Fig3.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="800" data-original-width="997" height="514" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIdoUUXosnKFwbYePSo4cLpyRFDIUB5rVbRYFILjPloXcL6btdAKKO3uRN8zhmWz1q8CrwS4F5gl23VTTdt5q0uj3aNUo7XPe4nkHQiYfOzyVjrZvv6WZ4J8x8x1Ah750QzuEsT97uMJfXDXmm-aBT938fYNu-z8OcKpJ2h616_JuAjlcC11OAq305gg/w640-h514/RightHVProbe_Fig3.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. HV probe selections for measuring a 260 Vdc GaN transistor.</span></td></tr></tbody></table><p>Figure 2 shows the selections for probing a 260 Vdc GaN transistor:</p><p></p><ul style="text-align: left;"><li>Single-ended passive probes (Black) should <i>absolutely not </i>be used for any measurement of this device, because it poses a safety hazard due to the floating nature of the signal.</li><li>A high-voltage differential probe (Yellow) may be <i>used with caution</i>, but there may be performance trade offs due to circuit loading, and it may not have sufficient bandwidth for higher speed GaN signals.</li><li>The <i>best option</i> (Green) is the single-ended fiber-optic isolated probe, the <a href="https://teledynelecroy.com/probes/high-voltage-optically-isolated-probes" target="_blank">DL-ISO</a>, because only it has the isolation, CMRR <i>and </i>bandwidth required for GaN device measurements.</li></ul><p></p><p>In a future post, we'll go over more of the reasoning behind this selection when we discuss probing requirements for GaN power semiconductor measurements.</p><p>There are many considerations to selecting the best high-voltage probe. The High-voltage Probe Selection Guide on the Teledyne LeCroy website is the starting point for choosing the best high-voltage probe for your application. Based on your needs, it provides usefully documented recommendations for any of the Teledyne LeCroy high-voltage probe offerings. </p><p>To try the High-voltage Probe Selection Guide, visit: <a href="https://teledynelecroy.com/powerprobes">teledynelecroy.com/powerprobes</a></p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-33377937755874831972022-08-22T08:00:00.008-04:002022-08-22T08:00:00.171-04:00Physical-Layer Collision Avoidance in 10Base-T1S Automotive Ethernet<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaJ9sVXAzBhgUtqvLn9VqyE5XkBK3kTBBtGkUXQbadv73nWJ2hyD4U2jPUwOSSsxxEKPhLium2ibUB7-cJHZcIDs_nIGRqHeFGDUFoLkZt0ak9SN5jTBQEma5m6BIWFPqXGN6JKsZLNME0bWbLdKyMed8iq1DiXl-YNwFgdWsfSE1leHmAs1X-Piq1XA/s1134/PLCA_Fig1.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="585" data-original-width="1134" height="165" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaJ9sVXAzBhgUtqvLn9VqyE5XkBK3kTBBtGkUXQbadv73nWJ2hyD4U2jPUwOSSsxxEKPhLium2ibUB7-cJHZcIDs_nIGRqHeFGDUFoLkZt0ak9SN5jTBQEma5m6BIWFPqXGN6JKsZLNME0bWbLdKyMed8iq1DiXl-YNwFgdWsfSE1leHmAs1X-Piq1XA/s320/PLCA_Fig1.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Fig.1, 10Base-T1S PLCA cycle. If there is no data<br />traffic (top), only BEACONs are seen on the bus. <br />Data from a node (bottom) will expand the time <br />between two BEACONs.</td></tr></tbody></table>10Base-T1S (IEEE 802.cg) is a variant of <a href="https://blog.teledynelecroy.com/2021/06/automotive-ethernet-in-vehicle.html" target="_blank">Automotive Ethernet</a> that supports half-duplex and full-duplex
communication, allowing either a point-to-point direct connection between two
nodes, or use of a multidrop topology with up-to-eight nodes connected on a
single 25 m bus segment.<p></p><p class="MsoNormal"><o:p></o:p></p>
<p class="MsoNormal">Multidrop cabling of one bus line provides options to extend
and scale with fewer physical wires and less weight than point-to-point topologies<span style="line-height: 115%;">. With minimum connector space at the ECU, the bus line can
be expanded simply by adding sensor units. A bus line with additional sensor
units for ultrasonic and short-range radar is an example of how multidrop
cabling can be scaled. </span><span style="font-size: 11pt; line-height: 115%;"> <o:p></o:p></span></p><p class="MsoNormal"><span style="color: black; line-height: 115%; mso-bidi-font-family: Arial; mso-bidi-font-size: 10.0pt;">Among the main objectives</span> of the
10Base-T1S PHY layer are reconciliation of transmissions from a variety of
mediums, ensuring cooperative behavior by the nodes on a multidrop bus. One
way it does this is through the use of Physical-Layer Collision Avoidance (PLCA)
technology to <span style="color: black; line-height: 115%; mso-bidi-font-family: Arial; mso-bidi-font-size: 10.0pt;">minimize dead time and avoid
collisions. In this post, we'll describe the workings of PLCA and in a future post, how you can debug PLCA timing issues using an <a href="https://teledynelecroy.com/oscilloscope/" target="_blank">oscilloscope </a>with the <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=681&groupid=88" target="_blank">10Base-T1S TDME</a> software.<span></span></span></p><a name='more'></a><span style="color: black; line-height: 115%; mso-bidi-font-family: Arial; mso-bidi-font-size: 10.0pt;"> <o:p></o:p></span><p></p>
<p class="MsoNormal">Essentially, PLCA establishes a transmission cycle used to
choreograph Transmit Opportunities (TOs) on the bus. As with a group of
individuals participating in a team-building exercise, if all nodes were
chaotically speaking their minds at once, nothing would be heard properly and nothing
would get accomplished in the time allotted. A PLCA transmit cycle establishes
the opportunities to speak and the order in which nodes can be heard, while
leaving enough flexibility that time is not wasted waiting for those who have
nothing to say.<span></span></p><p class="MsoNormal">In PLCA, each node (aka PHY) is assigned with a unique PHY
ID, and only the PHY device that owns the transmit opportunity is allowed to
send data. The transmit opportunities are allocated in a round-robin algorithm
starting from PHY ID = 0, which is allocated to the Master. Nodes can initiate
a transmission only during the transmit opportunity that matches their own node
ID. A new cycle is started when the Master node sends a synchronization pattern
called the BEACON to signal the start of the PLCA cycle. <o:p></o:p></p>
<p class="MsoNormal">The PLCA cycle itself consists of the BEACON followed by N+1
time slots, allowing N+1 variable size DATA packets to be sent. During their
transmit opportunity, a PHY may immediately transmit a packet or must transmit
a COMMIT pattern of SYNC symbols to compensate for any MAC latency and to buy
additional time before transmitting a packet. Nodes can enlarge the time slot
to accommodate larger transmissions and can burst high priority messages. The
other nodes will wait for a node to complete transmission before the cycle
moves to the node with the next transmit opportunity. A new time slot starts if
nothing is transmitted within a defined time (TO_TIMER) or at the end of any
packet transmission.</p><p class="MsoCaption"><o:p></o:p></p>
<p class="MsoNormal">At the beginning of each transmission cycle, Node 1 on the bus is first assigned the transmit opportunity. If there is no DATA for this node to transmit and it cannot COMMIT, it cedes its transmit opportunity to the next node on the bus.</p><p class="MsoNormal">In attempting to understand the PLCA cycle, it may help to
visualize the use of a variable delay line to relate transmit opportunities to
each node on the bus. The driving scheme of PLCA is to sync TO_TIMERs so that
the max latency consistently remains less than one PLCA cycle. TO_TIMER is very
short (typically 20 bits), so there is a negligible loss of throughput when
waiting for PHYs that have nothing to transmit.<o:p></o:p></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRuPdW1giGTxfBraUVFfur5HHi3OMKKEUjYO3ROsIsXTalX_5SKcqUX7VhOvv_W52lwRNy6luldqReD8UTMLF6HZ4xCXlhbt8pbHNH-G7EHh9wwthHksq1sONvSYPInsE0PNYOEatDOkqq71DhgYlpOlQazTi28COSKxv7Yz17ateuGxK8gqwb_G3AkA/s1485/PLCA_Fig2.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="382" data-original-width="1485" height="165" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRuPdW1giGTxfBraUVFfur5HHi3OMKKEUjYO3ROsIsXTalX_5SKcqUX7VhOvv_W52lwRNy6luldqReD8UTMLF6HZ4xCXlhbt8pbHNH-G7EHh9wwthHksq1sONvSYPInsE0PNYOEatDOkqq71DhgYlpOlQazTi28COSKxv7Yz17ateuGxK8gqwb_G3AkA/w640-h165/PLCA_Fig2.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span face=""Arial",sans-serif" style="font-size: 10pt; line-height: 115%; mso-ansi-language: EN-US; mso-bidi-font-family: "Times New Roman"; mso-bidi-font-size: 11.0pt; mso-bidi-language: AR-SA; mso-bidi-theme-font: minor-bidi; mso-fareast-font-family: Calibri; mso-fareast-language: EN-US; mso-fareast-theme-font: minor-latin;">Fig. 2, Minimum latency PLCA cycles. No one has anything
to transmit in cycle 1, so total latency is equal only to the number of nodes
times the TO_TIMER. Only Nodes 1 and 3 have transmissions in cycle 2, so all
the other nodes cede their transmit opportunity. </span></td></tr></tbody></table><br /><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDS2FOQKT1bOaDrxCmbWc0dsw7Y0XNPWUwpymXwFMjyFvf8l9MZg6fhvKrWfLgXapjsNmWpq-6jK7Imq7i7XR60NOAZ4SXEu4O0KZErjLFbJFwpjTGZqbozYazkSfPuM32k3TEseYpQy8VJp-OC7_ZI1EK5C2EuHBUH4_QCxsfnFc8No90baA2AFxziA/s1491/PLCA_Fig3.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="203" data-original-width="1491" height="88" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDS2FOQKT1bOaDrxCmbWc0dsw7Y0XNPWUwpymXwFMjyFvf8l9MZg6fhvKrWfLgXapjsNmWpq-6jK7Imq7i7XR60NOAZ4SXEu4O0KZErjLFbJFwpjTGZqbozYazkSfPuM32k3TEseYpQy8VJp-OC7_ZI1EK5C2EuHBUH4_QCxsfnFc8No90baA2AFxziA/w640-h88/PLCA_Fig3.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span face=""Arial",sans-serif" style="font-size: 10pt; line-height: 115%; mso-ansi-language: EN-US; mso-bidi-font-family: "Times New Roman"; mso-bidi-font-size: 11.0pt; mso-bidi-language: AR-SA; mso-bidi-theme-font: minor-bidi; mso-fareast-font-family: Calibri; mso-fareast-language: EN-US; mso-fareast-theme-font: minor-latin;">Fig. 3, Maximum latency PLCA cycle. Every node has the
maximum size packet and sends a COMMIT <br />
while waiting for the MAC.</span></td></tr></tbody></table><p class="MsoNormal">The benefit of this system is that the individual nodes
track TO_TIMER independently following the BEACON. Because nodes with no data
to transmit will yield their transmit opportunity, the short window afforded by
the TO_TIMER ensures a minimal loss of throughput or increase of latency. This
variable delay is similar to TDMA, but PLCA is not a fixed or absolute
reference for timed packets; instead, it adjusts according to the transmit
needs of each node on the bus.</p><p class="MsoNormal"><o:p></o:p></p><h4 style="text-align: left;">Also see:</h4><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2022/08/the-difference-between-10base-t1s.html" target="_blank">The Difference Between 10Base-T1S and 10Base-T1L</a></p><p class="MsoNormal"><a href="https://blog.teledynelecroy.com/2021/06/automotive-ethernet-in-vehicle.html" target="_blank">Automotive Ethernet in the Vehicle</a></p><p class="MsoNormal"><br /></p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-60289236339529702922022-08-15T08:00:00.014-04:002024-01-09T08:27:48.116-05:0010Base-T1S Automotive Ethernet vs. 10Base-T1L Industrial Ethernet<p></p><table cellpadding="5pt" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizhokuCINLikZdUAsyQ0Y5OI9xiVQijj8DDX4wmYXIJlqc5dvJajaRbLDnTrJeUIYjgSQj-U2Ra9Aho2za8dULl800xzDve2BHy4BIjQ9O0n36cmk9gmkX9_TyNSpuvmqAsnQT-P7LBPPs/s1082/T1SvsT1L_Fig1.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="327" data-original-width="1082" height="121" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizhokuCINLikZdUAsyQ0Y5OI9xiVQijj8DDX4wmYXIJlqc5dvJajaRbLDnTrJeUIYjgSQj-U2Ra9Aho2za8dULl800xzDve2BHy4BIjQ9O0n36cmk9gmkX9_TyNSpuvmqAsnQT-P7LBPPs/w400-h121/T1SvsT1L_Fig1.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1: 10Base-T1S and 10Base-T1L differ primarily in<br />reach, encoding methods, topology and applications.</td></tr></tbody></table>10Base-T1S, a variant of <a href="https://blog.teledynelecroy.com/2021/06/automotive-ethernet-in-vehicle.html" target="_blank">Automotive Ethernet</a>, and 10Base-T1L, also known as Industrial Ethernet, are Single Pair Ethernet (SPE) protocols described in IEEE 802.cg standards. Both offer the same 10 Mb/s communication speed using a single, unshielded twisted pair (T1), but differ in specifics of reach, encoding schemes and topologies, as well as their principal applications.<span><a name='more'></a></span><p></p><p>10Base-T1S (S stands for short reach) has a reach of up to 25 m, more than enough for in-vehicle applications. 10Base-T1L (L stands for long reach) allows for the same 10 Mb/s speed over a reach of 1,000 m. </p><p></p>10Base-T1S uses Differential Manchester Encoding (DME). With DME, the clock is embedded and the data is sampled between the clocked edges. Instead of a specific logic-high/low voltage level, the bits are based on the presence or absence of any transition within the clock period. Because it lacks a DC component, this encoding scheme allows electrical connections easy galvanic isolation, ensuring the signal never remains at logic low or logic high for an extended period of time, which allows for versatility in a number of automotive applications.<p></p><p></p><table cellpadding="5pt" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZJsG60O0cst8nG6k0mSRJ3Nna_dTGvAc84rXebVoIPJhaOAvo9PM2tqw8RNRu4NFpIqKAg-D8ZyY4-8kaJQvS-9HOBDWEJTDaG8QORfEu7QOHxKTn_rd_TgWTwblEfhiCHTVUdEwJhoKw/s1053/Fundamentals+AutoENET+Fig4.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="575" data-original-width="1053" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZJsG60O0cst8nG6k0mSRJ3Nna_dTGvAc84rXebVoIPJhaOAvo9PM2tqw8RNRu4NFpIqKAg-D8ZyY4-8kaJQvS-9HOBDWEJTDaG8QORfEu7QOHxKTn_rd_TgWTwblEfhiCHTVUdEwJhoKw/s320/Fundamentals+AutoENET+Fig4.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 2: PAM3 Encoding.</td></tr></tbody></table>10Base-T1L utilizes PAM3 Pulse Amplitude Modulation encoding. In PAM3 signal modulation, information is encoded in the amplitude of a series of signal pulses. This results in simplified receiver and transmitter design, easy transmission over a single pair of wires, more bits transmitted in a symbol, and higher data rate links. <p></p><p>These two protocols are further differentiated by the topologies they employ. 10Base-T1S supports half-duplex and full-duplex communication, allowing either a point-to-point direct connection between two nodes, or use of a multidrop topology with up-to-eight nodes connected on a single 25 m bus segment. 10Base-T1L supports a full-duplex link that can include up to 10 connectors. </p><p>To better understand the differences between these two protocols, we can explore the ways these standards are applied in the growing sectors of Automotive and Industrial Automation. </p><p>As in-vehicle electronics grow in volume and complexity to support the goal for autonomous driving, we find 10Base-T1S Automotive Ethernet used to enhance In-Vehicle Network (IVN) architecture. It is most commonly used to connect sensors, microphones and speakers to powertrain, car body and infotainment Electronic Control Units (ECUs). Because 10Base-T1S provides a higher bandwidth, it allows IVN applications to operate with higher quality data compared to some of the legacy IVN protocols such as MOST, CAN, LIN and FlexRay. Plus, a combination of 10Base-T1S and other Automotive Ethernet protocols allows a single software framework to be used from the lowest to highest speed ranges. As discussed in <a href="https://blog.teledynelecroy.com/2021/06/fundamentals-of-automotive-ethernet.html" target="_blank">other posts on this blog</a>, standard Ethernet is not suited for use in IVN, partly because the 100 m reach of standard Ethernet is unnecessary for a vehicle, and overall, the technology does not hold up to the stringent EMC and EMI requirements of the automotive industry. </p><p>By enabling point-to-point communication over distances up to 1000 m, 10Base-T1L provides a framework for industrial control and safety systems. In the context of Operational Technology (OT) networks, such as Remote, Intelligent Building, Industrial and Process Industries applications, 10Base-T1L replaces legacy, built-for-purpose protocols that pose challenges because they require complex gateway devices to communicate between domains, and experts trained to manage and maintain such outdated networks. By bringing the benefits of the single twisted pair to the factory floor, 10Base-T1L allows easy integration and standardization in areas of building and industrial automation. </p><p>Teledyne LeCroy offers the <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=681&groupid=88" target="_blank">10Base-T1S TDME</a> software trigger and decode software and the <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=646&groupid=140" target="_blank">QPHY-10Base-T1S</a> compliance test solution, including a <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=649&groupid=140" target="_blank">QPHY-10Base-T1-TDR</a> option that automates all required MDI S-parameter tests using the <a href="https://teledynelecroy.com/wavepulser" target="_blank">WavePulser 40iX</a>.</p><p>For more information about 10Base-T1 compliance testing, watch the on-demand webinar, <a href="https://go.teledynelecroy.com/l/48392/2021-04-27/86r6b2" target="_blank">How to Become an Expert in Automotive Ethernet Testing, Part 1</a>.</p><h4>See also:</h4><div><a href="https://blog.teledynelecroy.com/2021/11/what-is-differential-manchester-encoding.html" target="_blank">What Is Differential Manchester Encoding?</a></div><div><br /></div><div><a href="https://blog.teledynelecroy.com/2021/06/automotive-ethernet-mdi-s-parameter.html" target="_blank">Automotive Ethernet MDI S-parameter Testing</a></div><p><a href="https://blog.teledynelecroy.com/2021/06/automotive-ethernet-in-vehicle.html" target="_blank">Automotive Ethernet in the Vehicle</a></p><p><a href="https://blog.teledynelecroy.com/2021/06/fundamentals-of-automotive-ethernet.html" target="_blank">Fundamentals of Automotive Ethernet</a></p><p><br /></p><p><br /></p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-32319238174662639612022-08-08T08:00:00.013-04:002022-08-11T12:07:54.422-04:00Using TF-USB-C-HS for USB 3.2 PHY-Logic Layer Debug<div><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi299HNO1L5zSD2Nr9VXJ2IdmuTtMonyC7yRmB2TNsRx4ADEUYqczoKxaKvz93pwzdRmpRchRmpNLXpzsBG99ZKPCjohoL2DatX1T64CdCDuP98wTyK27z76XyjpEI2JEvW-6DHcHyqOIDCy5n0FA7ITo3ewFjzW2OQJnTiplp93sHIXhwEcNZxOZZ2fg/s1957/USB3.2PHYlogic_Fig1.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1103" data-original-width="1957" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi299HNO1L5zSD2Nr9VXJ2IdmuTtMonyC7yRmB2TNsRx4ADEUYqczoKxaKvz93pwzdRmpRchRmpNLXpzsBG99ZKPCjohoL2DatX1T64CdCDuP98wTyK27z76XyjpEI2JEvW-6DHcHyqOIDCy5n0FA7ITo3ewFjzW2OQJnTiplp93sHIXhwEcNZxOZZ2fg/w400-h225/USB3.2PHYlogic_Fig1.PNG" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1. USB 3.2 electrical decoding with ProtoSync<br />view of protocol packets, captured using TF-USB-C-HS.<br />Click on any image to enlarge it.</td></tr></tbody></table>In a USB-C connector, link training for USB 3.1/3.2 is negotiated using an LTSSM (Link Training and Status State Machine) through electrical signaling on the <a href="https://blog.teledynelecroy.com/2022/06/what-happens-when-you-connect-usb-c.html" target="_blank">TX1/RX1 and TX2/RX2 connector pins</a>. Link training must be completed on the link before high-speed data transactions can occur. One problem you might encounter during link training is a failure to train to USB 3.2 Gen 2 specifications. Teledyne LeCroy customers report that most system-interoperability problems are caused by either link-training or sideband-negotiation failures, which in turn can result from an electrical problem, a digital problem or a combination of both. </div><div><br /></div><div><a href="https://teledynelecroy.com/options/productdetails.aspx?modelid=11678&categoryid=11&groupid=170" target="_blank">TF-USB-C-HS</a> enables you to probe all points on the USB-C connector to measure and analyze live links. The insertion-loss profile of the included cable and coupon is tuned to be the equivalent of a golden 0.8-m USB Type-C cable, so you can replace a 0.8-m cable with the coupon and not experience any difference in link performance. The coupon also has a loop to allow a current probe to make load-current measurements, and the HS version is compatible with Teledyne LeCroy <a href="https://teledynelecroy.com/probes/dh-series-differential-probes" target="_blank">DH Series</a> probes for making high-speed differential measurements.</div><div><br /></div><div>We'll show how to trigger, acquire and decode to find problematic link training packets synchronous with the physical-layer electrical waveforms, so you can tell if the source of your interoperability problem is electrical, logical or both.<span><a name='more'></a></span></div><h3 style="text-align: left;">Equipment</h3><div>Required are:</div><div><ul style="text-align: left;"><li>4 Ch, ≥16 GHz, 40 GS/s real-time oscilloscope such as SDA/<a href="https://teledynelecroy.com/oscilloscope/wavemaster-sda-dda-8-zi-b-oscilloscopes" target="_blank">WaveMaster 8 Zi-B</a> or <a href="https://teledynelecroy.com/oscilloscope/labmaster-10-zi-a-oscilloscopes" target="_blank">LabMaster 10 Zi-A</a></li><li><a href="https://teledynelecroy.com/options/productseries.aspx?mseries=334&groupid=88" target="_blank">USB3.2 D</a> decoder software option</li><li>16 or 20 GHz differential probe (2 each), such as <a href="https://teledynelecroy.com/probes/probemodel.aspx?modelid=11369&categoryid=3&mseries=608&capid=102&mid=508" target="_blank">DH16-PL</a> or <a href="https://teledynelecroy.com/probes/probemodel.aspx?modelid=11370&categoryid=3&mseries=608&capid=102&mid=508" target="_blank">DH20-PL</a></li><li><a href="https://teledynelecroy.com/protocolanalyzer/usb" target="_blank">Voyager M310P, M310e or M4x</a> USB Protocol Analyzer </li></ul></div><div>Recommended are:</div><div><ul style="text-align: left;"><li><a href="https://teledynelecroy.com/options/productseries.aspx?mseries=287&groupid=88" target="_blank">ProtoSync option</a> for USB (requires installation of USB Protocol Suite software)</li><li><a href="https://teledynelecroy.com/sdaiii/" target="_blank">SDAIII-CompleteLinQ option</a> for eye diagram analysis of the live link</li></ul></div><h3 style="text-align: left;">Probing with the TF-USB-C-HS Test Coupon</h3><div>The TF-USB-C-HS is connected between the DUT and the Exerciser/Analyzer ports of a Voyager Analyzer (M310e/M310P or M4x), using the included USB-C cable (Figure 2). </div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivwtZXtwA9Aczp0zyLVdrEDf_x78kvQLGfu-rrM_IgIcjFdGIKbGFJ_j3PVjbDsqNaE-zbwhkw6mE4UHwMKUpwnFcdVaGjhdg8zK-nijOTPU-LPOTUwLuNB191gaHxbHxbhquIqzYl8wv-FLd0UOEGVs1kJdryATYwGnkd5yimzOGyD5K4UeB6rUBCgA/s1689/USB3.2PHYlogic_Fig2.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1321" data-original-width="1689" height="313" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivwtZXtwA9Aczp0zyLVdrEDf_x78kvQLGfu-rrM_IgIcjFdGIKbGFJ_j3PVjbDsqNaE-zbwhkw6mE4UHwMKUpwnFcdVaGjhdg8zK-nijOTPU-LPOTUwLuNB191gaHxbHxbhquIqzYl8wv-FLd0UOEGVs1kJdryATYwGnkd5yimzOGyD5K4UeB6rUBCgA/w400-h313/USB3.2PHYlogic_Fig2.PNG" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. Test setup for USB 3.x PHY-logic debug using protocol trigger.</span></td></tr></tbody></table><br /><div>Signals are input to the oscilloscope by way of the test coupon:</div><div><ul style="text-align: left;"><li>TX1 is input to A-row Upper Deck C1 using a DH Series differential probe.</li><li>TX2 is input to A-row C2 using same.</li><li>Optionally, sideband signals CC1/CC2 and Vbus can be monitored using passive probes on the B-row connectors of the oscilloscope. </li><li>The Voyager trigger out signal is connected to oscilloscope Ext In.</li></ul></div><h3 style="text-align: left;">Protocol Analyzer Triggering</h3><div><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXXjpvaixS2srK5cDvBBohmkA8k53-CkO36CVu2PnTZ8REtHow_CZrTATUYRRCYsT02PeLhWkP38ZzRM-cB4DWY1glmO0PsO6VlXm52huIbms3o9FNFhqZjLLyaj0VnD5O2u9OgsYce_dMjia1R82DPbpLda1fbyW1uheFHzUdSDoW3eUASRIbmzw2_A/s2257/USB3.2PHYlogic_Fig3.PNG" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1377" data-original-width="2257" height="244" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXXjpvaixS2srK5cDvBBohmkA8k53-CkO36CVu2PnTZ8REtHow_CZrTATUYRRCYsT02PeLhWkP38ZzRM-cB4DWY1glmO0PsO6VlXm52huIbms3o9FNFhqZjLLyaj0VnD5O2u9OgsYce_dMjia1R82DPbpLda1fbyW1uheFHzUdSDoW3eUASRIbmzw2_A/w400-h244/USB3.2PHYlogic_Fig3.PNG" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. Voyager protocol analyzer view of the polling state <br />packets of the USB 3.2 LTSSM.</span></td></tr></tbody></table>Link training issues usually first show up while doing Link Layer or USB Type-C-specific tests using a Voyager protocol analyzer. The protocol analyzer has a rich set of Link Training Packets (LTP) and higher layer analysis of the USB 3.2 LTSSM (Figure 3). In order to trigger an oscilloscope on the area of interest, is necessary to first identify where in the protocol trace the problem is occurring, then set up the protocol analyzer to send a trigger pulse to the oscilloscope at that time. </div><div><br /></div><div>For instance, during Link training, you can send a trigger pulse on SCD1, SCD2, LBPM or an LMP (Link Management Packet). As each trigger event occurs in the signal, the event is marked on the protocol trace and a pulse is sent from the Trigger Out connector of the protocol analyzer to the Ext In trigger input of the oscilloscope, enabling it to capture the electrical signals at virtually the same time. </div><div><br /></div><h3 style="text-align: left;">Oscilloscope Triggering and Decoding</h3><div>Set up the oscilloscope for an Edge trigger using the Ext In Source.</div><div><br /></div><div>Set up the USB 3.2 D software for Gen2x2 decoding, with One Differential Probe selection. (Note that our example uses acquisitions of Lane0 and Lane1 saved to memories M1 and M2. When probed live, these signals would be on C1 and C2.)</div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg62hK1VC23Rb0CC4Z2ovjqRKdW8QdSfaTHlmrk4hxyueFHUcXEWkPFnU_r29KptQ9kLnTGKuiFfoV42VXElYlId4R-gb4C988hCyChFcRTmVvCCX5-_dMoKsUtcIOcXd0DhCm_sF3Kwv6NZP4n_G4vecASdq8QDJ7X4XCZ7oyZLfs7wbhWX_XGw3GOxg/s2252/USB3.2PHYlogic_Fig4.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="314" data-original-width="2252" height="90" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg62hK1VC23Rb0CC4Z2ovjqRKdW8QdSfaTHlmrk4hxyueFHUcXEWkPFnU_r29KptQ9kLnTGKuiFfoV42VXElYlId4R-gb4C988hCyChFcRTmVvCCX5-_dMoKsUtcIOcXd0DhCm_sF3Kwv6NZP4n_G4vecASdq8QDJ7X4XCZ7oyZLfs7wbhWX_XGw3GOxg/w640-h90/USB3.2PHYlogic_Fig4.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. Setup for USB 3.2 Gen2x2 decoder.</span></td></tr></tbody></table><div><br /></div><div>After acquiring, use the decoder Search or Filter feature to find the packet type of interest, which appears in the Type column of the decoder result table. Clicking that row of the table will zoom to the same time in the electrical trace. If you also have the ProtoSync display open (as in Figure 1), you'll also see exactly which protocol packet is involved.</div><div><br /></div><h3 style="text-align: left;">Eye Measurements</h3><div><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEga6KtZKOr2w7RMvEbd_A4PGYdB7JaQjOf6GRHFql817QV4Y2NILSYCbzM1osMT1tv5TFOZckYdbBtIMxMvbwDMhCCk_c1UMY7u5oQ2eOQCwbb6vxk8dGWb0p8eXbvP3y45sByL6JlrF4poR1jcnq0dUgau1aY1qu5dzJqyyvpm1NZatNuVI4XZE_HUFA/s2259/USB3.2PHYlogic_Fig5.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1276" data-original-width="2259" height="226" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEga6KtZKOr2w7RMvEbd_A4PGYdB7JaQjOf6GRHFql817QV4Y2NILSYCbzM1osMT1tv5TFOZckYdbBtIMxMvbwDMhCCk_c1UMY7u5oQ2eOQCwbb6vxk8dGWb0p8eXbvP3y45sByL6JlrF4poR1jcnq0dUgau1aY1qu5dzJqyyvpm1NZatNuVI4XZE_HUFA/w400-h226/USB3.2PHYlogic_Fig5.PNG" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 5. Eye diagrams show signal integrity of live link <br />during negotiations.</span></td></tr></tbody></table>A possible source of link training errors is poor signal quality coming from the transmitter. The TF-USB-C-HS provides a convenient way to perform serial data analysis measurements on the transmitters while in a live link. This is not a substitute for physical layer compliance testing, but it can be used to verify that the expected signal quality is coming from the two USB 3.2 transmitters, TX1 and TX2. </div><div><br /></div><div>If you have installed the SDAIII-CompleteLinQ oscilloscope option, a complete set of signal integrity tools is available, including jitter and eye diagram measurements and plots. You can use the eye diagrams to look at the electrical performance of the live link. If the signal is not optimized for the cable it is driving, you may see an eye diagram that has too much or too little equalization. The ISI Plot allows you to evaluate the effect of different pre-emphasis presets on the transmitted eye. </div><div><br /></div><div>Multi-lane testing with SDAIII-CompleteLinQ also allows you to see both transmitter signals side-by-side in order to determine if there are lane-dependent SI issues that might be contributing to poor link performance. </div><div><div><br /></div></div><div>You can download these instructions in our PDF application note, "Using TF-USB-C-HS to Debug USB 3.1/3.2 PHY-Logic and Link Training."</div><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2022/06/what-happens-when-you-connect-usb-c.html" target="_blank">What Happens When You Connect a USB-C Cable</a></div><div><a href="https://blog.teledynelecroy.com/2021/12/usb4-alt-mode-testing-dpaux-and-usb-pd.html" target="_blank">USB4 Alt-Mode Testing: DP-AUX and USB-PD</a></div><div><a href="https://blog.teledynelecroy.com/2021/12/testing-displayport-20-vs-usb4-over-usb.html" target="_blank">Testing DisplayPort 2.0 vs. USB4 over USB Type-C</a> </div><div><br /></div><div><br /></div><div><br /></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-4960467518850232172022-08-01T08:00:00.171-04:002022-09-21T10:40:26.190-04:00Signal and Power Integrity Tutorial: Power Rail Probing for Rail Compression<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguiai9zlEEYunKR_ai2LgIoHlcLvJie74FsAQDZw4TfjnLtxJ1gZZO6oeZZeauifx_rBJWTWWuWKDJHii-FpVHxW9fUYsB3W510tIPpIq9OozGXZvDmHD7UPRp0lmDSEBCf15GYnBCeNhw1lCI_eQV1hcEbldmcHWsXq50Klukf0oy5HvaylH5CeULyQ/s624/BoardNoiseFig3.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="219" data-original-width="624" height="140" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguiai9zlEEYunKR_ai2LgIoHlcLvJie74FsAQDZw4TfjnLtxJ1gZZO6oeZZeauifx_rBJWTWWuWKDJHii-FpVHxW9fUYsB3W510tIPpIq9OozGXZvDmHD7UPRp0lmDSEBCf15GYnBCeNhw1lCI_eQV1hcEbldmcHWsXq50Klukf0oy5HvaylH5CeULyQ/w400-h140/BoardNoiseFig3.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. Equivalent circuit of a typical CMOS I/O <br />showing the connection from the on-die rails <br />and the board-level test points.</span></td></tr></tbody></table>By Prof. Eric Bogatin, <br />Teledyne LeCroy Fellow<div><br /></div><div>Excerpted by permission from the Signal Integrity Journal article, <a href="https://www.signalintegrityjournal.com/articles/2790-measuring-only-board-level-power-rail-noise-may-be-misleading" target="_blank">Measuring Only Board-level Power Rail Noise May Be Misleading</a></div><div><br /></div><div>Continued from <a href="https://blog.teledynelecroy.com/2022/07/signal-and-power-integrity-tutorial-how.html" target="_blank">Part 1</a>.</div><div><p><br /></p><h3 style="text-align: left;">Measuring Rail Compression on the Die</h3><p>In most applications, we do not have access to the bare die when the chip is assembled on the circuit board. If the IC package has not been instrumented with special pass-through features connecting the rails on the die to board pins, we have to rely on a special trick. [The use of a <a href="https://blog.teledynelecroy.com/2018/08/more-on-quiet-low-io-drivers-and-ground.html" target="_blank">quiet HIGH and quiet LOW</a>]</p><p>When the I/Os of a chip all share the same power and ground rails, which is often the case in small microcontroller devices, designated I/Os can be used as sense lines to measure externally the power rails on the die.<span></span></p><a name='more'></a><p></p><p>In digital CMOS outputs, the driver connects its output to either the Vdd or the Vss rails when its output is set to a HIGH or a LOW, respectively. This means that an I/O set as a HIGH or a LOW provides a direct connection to elsewhere on the board from which the Vdd or Vss rails can be measured, relative to the local ground on the board.</p><p>We call these special I/Os a quiet HIGH and a quiet LOW line. When they are set as a fixed value, their output voltage should not change. Any voltage variation on these lines is only due to noise either on the rail to which they connect or picked up somewhere along their signal-return paths. If these connections are designed as uniform transmission lines with a solid return plane, with other signals far away, the voltage measured at these test points will be dominated by the voltage of the on-die rail relative to the local board ground of the test point.</p><p></p><p>All the measurements of the test points on the board are done as single-ended. This means the measured voltage is the voltage of the test point relative to the local ground location where the oscilloscope probe’s ground makes contact with the board ground plane. </p><p>The voltage measured at the Vdd test point is not actually the Vdd on the die. It is the Vdd on the die relative to the board ground. If there is ground bounce noise on the Vss rail, its voltage, and the entire chip’s Vss rail, may bounce relative to the local board ground. This bounces the Vdd rail the same amount, relative to the board ground. </p><p>What we really care about is the voltage rail on the die between the Vdd and Vss rails. This is Vdd – Vss, with each of them measured relative to the same board ground reference point. We sometimes refer to this value as rail compression. It is how the voltage rail on the die compresses due to currents switching.</p><p>What we actually measure is the voltage on the test point relative to the local board ground plane. As long as there is no additional noise picked up on the test lines from where they leave the package to where they reach the test point, the measured voltage difference between the Vss and Vdd test points would be equal to the rail compression on the die.</p><p>The process is then to measure the quiet HIGH and quiet LOW test points when other I/Os switch. When the oscilloscope is triggered by one of the I/Os switching, the rail compression can be measured from the Vdd and Vss quiet lines....The rail compression can be displayed on the screen using an oscilloscope math function calculating Vdd – Vss. </p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0PQhNZ-zCnkI4RUvN-v0QFKAww8VrK5JA_wLtRDNaH4cpYx1PO5X_m4pYDdX5YfcqB5Tprso1y_kgTbV7kYvGFR-DvX207BJIq7gIYFmoaaYSx198wRtlhGwFTb9_2A6mvX1JVyX9LGKNjfGcSSpKbUC6DQ0khZDC2Kj4Yt3Rg1PkAAlbfz4UZKNErQ/s325/BoardNoiseFig4.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="325" data-original-width="202" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0PQhNZ-zCnkI4RUvN-v0QFKAww8VrK5JA_wLtRDNaH4cpYx1PO5X_m4pYDdX5YfcqB5Tprso1y_kgTbV7kYvGFR-DvX207BJIq7gIYFmoaaYSx198wRtlhGwFTb9_2A6mvX1JVyX9LGKNjfGcSSpKbUC6DQ0khZDC2Kj4Yt3Rg1PkAAlbfz4UZKNErQ/w249-h400/BoardNoiseFig4.png" width="249" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. The rail compression is <br />the difference between the <br />measured voltage of the <br /></span><span style="text-align: left;">quiet Vdd and quiet Vss lines <br />relative to the local ground.</span></td></tr></tbody></table>In this example, the Vdd power rail was 3.3 V. The measured rail compression during the time at which the I/Os were switching was as much as 1.2 V. This is huge. It is so large that it affects the output signal rise time and would have caused false triggering on other I/O lines. If this rail was also used by the core logic, bit errors would definitely be generated.<p></p><h3 style="text-align: left;">On-die Rail Noise and Board-level Rail Noise</h3><p>Using the quiet LOW and quiet HIGH sense lines gives a direct measure of the rail compression noise on the die itself. This is what is important, since it is this noise which will affect the correct functioning of the die and the impact from noise on false triggering.</p><p>But, suppose you had not instrumented the chip and did not know the voltage noise on the die itself. Suppose you only measured the voltage noise on the power rail on the board, relative to the local board ground. What would you see?</p><p>Also on this test board is a test point connected to the 3.3 V output of the LDO. At this point, we measure the voltage noise on the board. It is exactly the same net as the Vdd rail on the die, but it is located some distance away from the on-die test point, and on the other side of the low-pass filter from the source of the noise.</p><p>The on-die rail compression was a dip of 1.2 V, while the on-board voltage level changed by less than 0.025 V. All voltages are displayed at the same scale.</p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEineRodTTLw30U-QOJH3yU2qn9Ck_rg9oOWEzBOZygXCzNBkXGQr6Y_ihQQSAhJKiyrPSDYjihVu_r9BO0mfrzEiaQJCQ24VZSgNmrPbT2C0GzUVtVjIDqdH43t-69eQC9tHBaaJW5ojw8CtFu5VlVbRfDjh6Q--yNRXwAQC8Hxs1qO0qedCVfLF7R0dQ/s360/BoardNoiseFig5.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="290" data-original-width="360" height="258" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEineRodTTLw30U-QOJH3yU2qn9Ck_rg9oOWEzBOZygXCzNBkXGQr6Y_ihQQSAhJKiyrPSDYjihVu_r9BO0mfrzEiaQJCQ24VZSgNmrPbT2C0GzUVtVjIDqdH43t-69eQC9tHBaaJW5ojw8CtFu5VlVbRfDjh6Q--yNRXwAQC8Hxs1qO0qedCVfLF7R0dQ/s320/BoardNoiseFig5.png" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 5. The on-die rail compression was a dip<br />of 1.5 V, while the on-board voltage level<br />changed by less an 0.025 V. <br />All voltages are displayed at the same scale.</td></tr></tbody></table>On the oscilloscope trace in this figure, the measured on-board 3.3 V rail is about 0.025 V, a very small amount of noise when the I/Os switch while there is 1.2 V of compression on the die. This is because the noise on the die, the aggressor signal, has to get through the low-pass filter composed of the package lead inductance and the local decoupling capacitors to get to the LDO, the victim location. The pole frequency of the low-pass filter is about 1 MHz in this board. Since the rise time of this noise is about 1 ns, its bandwidth is about 350 MHz. Very little of this noise gets through the 1 MHz low-pass filter. <p></p><p>If we had measured the voltage noise on the board and seen just 0.025 V amplitude noise, we would have concluded that the power rail noise was very low and insignificant, not to worry. In fact, the actual on-die compression was more than one-third the entire power rail, large enough to affect robust functioning of the chip.</p><p>Without this sort of on-die measurement, you would have no idea your product was so close to failure, until some customer ran it through some operation that was sensitive to this large of an on-die noise level. Without the diagnostic of knowing how large the on-die power rail noise was, finding the root cause of the problem would be as difficult as hunting a snipe. </p><h3 style="text-align: left;">Summary</h3><p>It is important to think about an equivalent circuit model of your PDN so you can see in your engineering mind’s eye the low-pass filters between different nodes on the same net of your PDN. Measuring the power rail noise on the board is no indication of the noise on the die. Without a way of actually measuring the power rail voltage noise on the die, you have no idea how much noise is present.</p><p>If you use measurements of the noise on the board as an indication of the goodness of various design decisions, be careful you are not drawing false conclusions. </p><p>Implementing the technique of using a quiet HIGH and quiet LOW I/O pin is a simple way of opening up a small window onto what is happening with the power rail of your die.</p><p>***********************************************************************************</p><p>For more information, watch these two free webinars by Prof. Eric Bogatin:</p><p><a href="https://go.teledynelecroy.com/l/48392/2021-05-03/874z78?&utm_source=website&utm_medium=blog&utm_campaign=21-12-07-power-integrity-masters-series-8&utm_content=__" target="_blank">Practical On-die Power Integrity Measurements</a></p><p><a href="https://go.teledynelecroy.com/l/48392/2018-12-18/79zd6q" target="_blank">Secrets To Successful Power Rail Measurements</a></p><h4 style="text-align: left;">Also see:</h4><p><a href="https://blog.teledynelecroy.com/2021/01/situational-awareness-impact-of.html" target="_blank">Situational Awareness: The Impact of the Interconnect</a></p><p><a href="https://blog.teledynelecroy.com/2018/08/more-on-quiet-low-io-drivers-and-ground.html" target="_blank">More on Quiet-Low I/O Drivers and Ground Bounce</a></p><p><a href="https://blog.teledynelecroy.com/2018/08/about-ground-bounce-and-how-to-measure.html" target="_blank">About Ground Bounce and How to Measure It</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/making-on-die-power-rail-measurements_24.html" target="_blank">Making On-Die Power-Rail Measurements (Part III)</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/making-on-die-power-rail-measurements_88.html" target="_blank">Making On-Die Power-Rail Measurements (Part II)</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/making-on-die-power-rail-measurements.html" target="_blank">Making On-Die Power-Rail Measurements (Part I)</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/measuring-shared-on-die-power-rails.html" target="_blank">Measuring Shared On-Die Power Rails</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/setting-stage-for-on-die-power-rail.html" target="_blank">Setting the Stage for On-Die Power-Rail Measurements</a></p><p><br /></p></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0PQhNZ-zCnkI4RUvN-v0QFKAww8VrK5JA_wLtRDNaH4cpYx1PO5X_m4pYDdX5YfcqB5Tprso1y_kgTbV7kYvGFR-DvX207BJIq7gIYFmoaaYSx198wRtlhGwFTb9_2A6mvX1JVyX9LGKNjfGcSSpKbUC6DQ0khZDC2Kj4Yt3Rg1PkAAlbfz4UZKNErQ/s325/BoardNoiseFig4.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="325" data-original-width="202" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0PQhNZ-zCnkI4RUvN-v0QFKAww8VrK5JA_wLtRDNaH4cpYx1PO5X_m4pYDdX5YfcqB5Tprso1y_kgTbV7kYvGFR-DvX207BJIq7gIYFmoaaYSx198wRtlhGwFTb9_2A6mvX1JVyX9LGKNjfGcSSpKbUC6DQ0khZDC2Kj4Yt3Rg1PkAAlbfz4UZKNErQ/s320/BoardNoiseFig4.png" width="199" /></a></div><br />Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-55824751167831008232022-07-25T08:00:00.135-04:002022-09-21T10:50:43.914-04:00Signal and Power Integrity Tutorial: How PDN Design Affects Board-level Noise<p></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody><tr><td style="text-align: center;"><img border="0" data-original-height="865" data-original-width="1127" height="246" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQqARorLLC7uBn6bVvwQcsj3XREO8gOSg7gTCL9uD3_4t9MO0fvWhLb-cAHiufr297X2UkcbtynE58rPW2rzomF9T78k9m_hgezeZhwHA4wz2H8orweObGP_oVmQDrz7LfFNrX1KrSJOfWOcz6aF9EEeoNf3C2iyljYALiGxW83UzklxKP_eRwdM2H5w/s320/Fig1_BLNoise_Pt1.PNG" style="margin-left: auto; margin-right: auto;" width="320" /></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. Oscilloscope traces resulting from <br /></span>measuring <span style="text-align: left;">a 3.3. V power rail with a 10x probe <br />versus a coaxial connection, with an <br />adjacent 10x probe acting as an RF antenna.</span></td></tr></tbody></table>By Prof. Eric Bogatin, <br />Teledyne LeCroy Fellow<div><br /></div><div>Excerpted by permission from the Signal Integrity Journal article, <a href="https://www.signalintegrityjournal.com/articles/2790-measuring-only-board-level-power-rail-noise-may-be-misleading" target="_blank">Measuring Only Board-level Power Rail Noise May Be Misleading</a><br /><p></p><p>In our blog, we’ve presented a lot about <a href="https://blog.teledynelecroy.com/2021/01/situational-awareness-impact-of.html" target="_blank">the impact of the interconnect</a> on <a href="https://teledynelecroy.com/oscilloscope/" target="_blank">oscilloscope</a> measurements, and how where you probe can be as important as how you probe. This article is an excellent demonstration of those very principles.</p><p>************************************</p><p>Power rail measurements are important because they can identify potential sources of noise before they become a problem. However, measuring only the power rail noise at the board-level may be a misleading indication of the noise the die actually sees. </p><h3 style="text-align: left;">Best Practices for Power Integrity Measurements</h3><p>Measuring a power rail on a board seems like a simple task. Like all measurements, it is easy to get a waveform on the oscilloscope’s screen, but it is difficult to have confidence you have eliminated the measurement artifacts and have a realistic measure of the actual signal present.<span></span></p><a name='more'></a><p></p><p>For example, the type of probe used to connect between the board/device under test (DUT) and the oscilloscope plays an important role. If you use a 10x probe, the tip loop inductance can act like an antenna and pick up RF noise either from the external environment, or from the near-field environment of the power rail itself. Figure 1 shows the voltage on a 3.3 V switch-mode power supply (SMPS) measured with a 10x probe, and the pick-up noise from an adjacent 10x probe shorted to itself, acting like an RF antenna. </p><p>In this example, an independent measurement of the power rail voltage was made at the same location as the 10x probe using a coaxial connection on the board with a coax cable directly into the oscilloscope. This connection did not pick up any external or near-field radiated emissions, and it did not attenuate the signal by a factor of 10 like the 10x probe did. This is an example of the impact different probing methods can have. </p><h3 style="text-align: left;">A Simple Model for the PDN</h3><p>Even with a good probing methodology, where you measure the power rail influences the noise you measure. It is important to always keep in mind that once the interconnects provide the correct connectivity, all they can do is add noise. Our job in designing the interconnects is to reduce the noise generated by the interconnects to an acceptable level.</p><p>In the power distribution path, the dominant parasitic introduced by the interconnects is inductance due to the loop inductance of the power and return conductors. The combination of the interconnect’s loop inductance and the discrete capacitors added to the power distribution network create embedded low-pass, LC filters. </p><p>Even though every conductor tied to the power rail is nominally the same net, the noise you would measure on different nodes of the power rail on the board will not be the same. What you measure depends on where the noise is measured. It depends on the victim; where the noise is generated, the aggressor; the frequency components of the noise; and the low-pass filters between the aggressor and the victim nodes. </p><p>Figure 2 is a simplified view of the PDN showing some of these low-pass filters.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPYub9SNejQzaQRm_5Pi4_1Vp4-PaokDKeyGcqrrYphcCE8UBzJzMcEvFpuSh3OHBSmZM3F-v4HcLgrXQyfxa-FJCctHnEoxyylA36uvDzfwmkil7I8pudIi9R35gRmR1XBSlI6YiC3yWqecH-P6gyMxuf0kcuQ5B-shPpUdGiOu7IFdvsZpX5nNWGnA/s1330/Fig2_BLNoise_Pt1.PNG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="440" data-original-width="1330" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPYub9SNejQzaQRm_5Pi4_1Vp4-PaokDKeyGcqrrYphcCE8UBzJzMcEvFpuSh3OHBSmZM3F-v4HcLgrXQyfxa-FJCctHnEoxyylA36uvDzfwmkil7I8pudIi9R35gRmR1XBSlI6YiC3yWqecH-P6gyMxuf0kcuQ5B-shPpUdGiOu7IFdvsZpX5nNWGnA/w640-h212/Fig2_BLNoise_Pt1.PNG" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2. A simplified view of the PDN showing some of the<br /></span> inductance from <span style="text-align: left;">the interconnects and the LC filters they create.</span></td></tr></tbody></table><p>Depending on the nature of the interconnects and the discrete decoupling capacitors, the pole frequency of the LC filters might range from a low of 10 kHz to a high of 10 MHz. For example, if the source of the noise is 50 kHz frequency components from the switching noise of the VRM, the higher frequency components may not be seen on the die, but some of the 50 kHz components may get through.</p><p>If the aggressor is the transient current from the die, the voltage noise on the die when depleting the on-die capacitance will drive dI/dt currents through the package lead inductance. While this noise will be measured on the die, since it generally has high frequency components, it will be filtered by the time it gets through the low-pass filters of the package lead inductance and board-level decoupling capacitors. It may not appear on a node on the board-level power rail.</p><p>To demonstrate this principle, I designed a simple board that creates on-die power rail noise from switching currents while allowing a direct measure of the on-die power rail voltage and the board-level power rail voltage. The circuit is just a simple clock that drives four of the inputs to a hex inverter chip. The other two pins of the hex inverter are used to measure the on-die voltages. </p><p>******************************************************************************</p><p>The use of the board is demonstrated in our next post, <a href="https://blog.teledynelecroy.com/2022/08/only-measuring-board-level-power-rail.html" target="_blank">Signal and Power Integrity Tutorial: Power Rail Probing for Rail Compression</a></p><p>For more information, watch these two free webinars by Prof. Eric Bogatin:</p><p><a href="https://go.teledynelecroy.com/l/48392/2021-05-03/874z78?&utm_source=website&utm_medium=blog&utm_campaign=21-12-07-power-integrity-masters-series-8&utm_content=__" target="_blank">Practical On-die Power Integrity Measurements</a></p><p><a href="https://go.teledynelecroy.com/l/48392/2018-12-18/79zd6q" target="_blank">Secrets To Successful Power Rail Measurements</a></p><h4 style="text-align: left;">Also see:</h4><p><a href="https://blog.teledynelecroy.com/2021/01/situational-awareness-impact-of.html" target="_blank">Situational Awareness: The Impact of the Interconnect</a></p><p><a href="https://blog.teledynelecroy.com/2018/08/more-on-quiet-low-io-drivers-and-ground.html" target="_blank">More on Quiet-Low I/O Drivers and Ground Bounce</a></p><p><a href="https://blog.teledynelecroy.com/2018/08/about-ground-bounce-and-how-to-measure.html" target="_blank">About Ground Bounce and How to Measure It</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/making-on-die-power-rail-measurements_24.html" target="_blank">Making On-Die Power-Rail Measurements (Part III)</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/making-on-die-power-rail-measurements_88.html" target="_blank">Making On-Die Power-Rail Measurements (Part II)</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/making-on-die-power-rail-measurements.html" target="_blank">Making On-Die Power-Rail Measurements (Part I)</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/measuring-shared-on-die-power-rails.html" target="_blank">Measuring Shared On-Die Power Rails</a></p><p><a href="https://blog.teledynelecroy.com/2018/01/setting-stage-for-on-die-power-rail.html" target="_blank">Setting the Stage for On-Die Power-Rail Measurements</a></p><p><br /></p><p><br /></p></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-22644443219525599822022-07-18T08:00:00.026-04:002022-12-19T12:23:28.810-05:00Six Principles of FFT Analysis Using Real-time Oscilloscopes<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1rei20Yq1QULcdF6_aFv3heVCIHSX3g9W0pR71ZyLcfKOK4mdv2vHo-o2CrznyekA2ireoj22rMkQACvKLio_Z13SyShnP4JRxrkNPwUpYWNUPtnEmS18knp__HwLOFb_NmSo7QUNABkl4vjbXE5GMS7FzNNJy0xXIna5zC6EcPNPdNxQyd74Bw8rtQ/s1880/RTSpecAn_Fig1.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="798" data-original-width="1880" height="170" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1rei20Yq1QULcdF6_aFv3heVCIHSX3g9W0pR71ZyLcfKOK4mdv2vHo-o2CrznyekA2ireoj22rMkQACvKLio_Z13SyShnP4JRxrkNPwUpYWNUPtnEmS18knp__HwLOFb_NmSo7QUNABkl4vjbXE5GMS7FzNNJy0xXIna5zC6EcPNPdNxQyd74Bw8rtQ/w400-h170/RTSpecAn_Fig1.PNG" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1. A 100 MHz sine wave in the time domain <br />and its spectrum in the frequency domain showing <br />the one peak at 100 MHz. Click on any image to enlarge.</span></td></tr></tbody></table>By Prof. Eric Bogatin, <br />Teledyne LeCroy Fellow<p></p><p>The following piece was published in <a href="https://www.signalintegrityjournal.com/articles/2920-six-principles-of-fft-analysis-with-real-time-oscilloscopes" target="_blank">Signal Integrity Journal</a> and is excerpted here by permission of Signal Integrity Journal.</p><p>***************************</p><p>We live in the time domain. This is where we measure all digital performance. But sometimes, we can get to an answer faster by taking a detour through the frequency domain. With these six principles, we can understand how an oscilloscope transforms time domain measurements into a frequency domain view. All six principles are applied “under the hood” by <a href="https://teledynelecroy.com/oscilloscope/" target="_blank">oscilloscopes with a built-in FFT function</a>. (Our note: Also by software packages designed for spectral analysis, such as the <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=631&groupid=144" target="_blank">SPECTRUM-1</a> and <a href="https://teledynelecroy.com/options/productseries.aspx?mseries=625&groupid=144" target="_blank">SPECTRUM-PRO-2R</a> options.)</p><h3 style="text-align: left;">1. The spectrum is a combination of sine wave components</h3><p>In the frequency domain, the only waveforms we are allowed to consider are sine waves. There are other special waveforms combinations of which can describe any time-domain waveform, such as Legendre polynomials, Hermite polynomials or even wavelets. The reason we single out sine waves for a frequency domain description, is that sine waves are solutions to second order, linear, differential equations—the equations found so often in electrical circuits involving resistor, capacitor and inductor elements. This means signals that arise or have interacted with RLC circuits are described more simply when using combinations of sine waves than any other function because sine waves naturally occur. <span></span></p><a name='more'></a><p></p><p>A sine wave measured by an oscilloscope with 1 million voltage-time [V(t)] data points in the acquisition buffer (Figure 1) is described by only three numbers in the frequency domain: a frequency value, an amplitude value and a phase value. This is a dramatic simplification of the original complex waveform.</p><h3 style="text-align: left;">2. Appending a waveform to itself infinitely creates a periodic waveform</h3><p>When we take a waveform in the time domain and transform it into the frequency domain, we end up with a collection of sine waves, each with a frequency value, an amplitude and a phase. In the time domain, we describe the measurements as an acquisition buffer with a total acquisition time, T, and a time interval between samples, 𝛥T. When we describe the same waveform in the frequency domain, we refer to the collection of all the sine wave components—each with a frequency, amplitude and phase—as the spectrum. </p><p>Unfortunately, we can only use the Discrete Fourier Transform (DFT) on a V(t) waveform that is periodic. If it is not periodic, we must artificially make it periodic. The trick we use to turn any arbitrary acquisition buffer of measured data into a periodic waveform is to take the acquisition buffer of total time, T, and repeat it forever in the past and forever in the future.</p><p>When we have this artificially repetitive waveform, we can apply the power of the DFT to mathematically calculate each frequency component in the spectrum. Here are the equations used to calculate the amplitude and phase of each frequency component:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9DiWiXizmasY79qZkqMhlJ9wYafbOQJ5cAnaybVrOT_y-AxE9Gd3Zs0et_epZ2Ys1z90atFlzIuIG3oaYXtEeM9Ow1fMxBCju8EV6y11zAT1vAnGXp0j7hPoRWHlL1yGI_8Edh74LUJ4TaUTU6H_o0-_7YlWL1n1-_zr17DSD9a0gAKLfAVIqnof3pA/s1120/RTSpecAn_Eq1.PNG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="101" data-original-width="1120" height="58" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9DiWiXizmasY79qZkqMhlJ9wYafbOQJ5cAnaybVrOT_y-AxE9Gd3Zs0et_epZ2Ys1z90atFlzIuIG3oaYXtEeM9Ow1fMxBCju8EV6y11zAT1vAnGXp0j7hPoRWHlL1yGI_8Edh74LUJ4TaUTU6H_o0-_7YlWL1n1-_zr17DSD9a0gAKLfAVIqnof3pA/w640-h58/RTSpecAn_Eq1.PNG" width="640" /></a></div><br /><p>These integrals create certain features in the spectrum. </p><h3 style="text-align: left;">3. Only discrete frequencies appear in a spectrum; the lowest is the fundamental </h3><p>In the calculated spectrum, only discrete frequency values appear. The lowest frequency component is called the <i>fundamental</i>. It is the lowest frequency sine wave we can fit into the acquisition buffer time. The period, P, of this lowest frequency sine wave is the total acquisition time, T. </p><p>Since P equals T, the fundamental frequency is:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizj6AAY26x9GWqCaGYzgHjexspuK0AiqEDLjtfgNKXLeKSQgV9ThDVlzyw9WIgNfOUyaVhHFyRRM76RRsk1RbpaIKsc1r2DQjIZSinsgWMbh99oVU5KzfjzRwdxtS-KGwadRZ0mcxuspX8RJKoryGxYdIAXzsA60qY5WpFg_IiOgAVrLb_ryXkc6UrAw/s371/RTSpecAn_Eq2.PNG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="136" data-original-width="371" height="73" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizj6AAY26x9GWqCaGYzgHjexspuK0AiqEDLjtfgNKXLeKSQgV9ThDVlzyw9WIgNfOUyaVhHFyRRM76RRsk1RbpaIKsc1r2DQjIZSinsgWMbh99oVU5KzfjzRwdxtS-KGwadRZ0mcxuspX8RJKoryGxYdIAXzsA60qY5WpFg_IiOgAVrLb_ryXkc6UrAw/w200-h73/RTSpecAn_Eq2.PNG" width="200" /></a></div><p></p><p>Each frequency component in the spectrum has a frequency that is only an integer multiple of the fundamental:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7M6_pqbCWA703U5gq2atNuacty1hhbqhzQ8ocBCRgyQTlDZXhHtGbStScm_HShqg3MYcifQlVZgLH7ZMSSkM7hkBPmCFEK0KHVxdQ_vgyNGFO6Iacy-NGHnhHhjuwZ6ogHo9zoizIWSmmBJyM0jECOX5Jtt-L3cWizzXh41SJK1SLqKypBt9G9uqDDg/s316/RTSpecAn_Eq3.PNG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="115" data-original-width="316" height="73" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7M6_pqbCWA703U5gq2atNuacty1hhbqhzQ8ocBCRgyQTlDZXhHtGbStScm_HShqg3MYcifQlVZgLH7ZMSSkM7hkBPmCFEK0KHVxdQ_vgyNGFO6Iacy-NGHnhHhjuwZ6ogHo9zoizIWSmmBJyM0jECOX5Jtt-L3cWizzXh41SJK1SLqKypBt9G9uqDDg/w200-h73/RTSpecAn_Eq3.PNG" width="200" /></a></div><p>Multiples of the fundamental are the only frequency components we will see in the spectrum. This means, the frequency spacing between each frequency component, or the <i>resolution</i>, is the fundamental frequency. If we want a higher resolution to distinguish closer spaced frequency features in the spectrum, we need to use a longer acquisition time in the oscilloscope. </p><h3 style="text-align: left;">4. The highest frequency is the Nyquist, or one-half the sample rate</h3><p>The highest frequency component in the spectrum is related to the time interval between the sampled points in the buffer. At a minimum, we need two measured V(t) points in one period in order to calculate a value for the amplitude and phase of that frequency component. This means the period of the highest frequency sine wave we can calculate is twice the time interval, or Pmax = 2 x 𝛥T. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPQr1zPbKA8CQgsOLYU0oDR-iNhA-8aobp3HCzsv5BakJYZFKzM2E4Gg_CAD_qgEFgAB6GVX76l1pQbkHOuFZRHKMOlGnvPFsnDNe8dEw6_7gFdj45okw--jZlmD6XZ_j03kUWiUDcLA0flkCJ6lLzmja1fEanRsbJp4S6v3CLJNHlEtiseHlaqv-ulA/s614/RTSpecAn_Eq4.PNG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="89" data-original-width="614" height="58" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPQr1zPbKA8CQgsOLYU0oDR-iNhA-8aobp3HCzsv5BakJYZFKzM2E4Gg_CAD_qgEFgAB6GVX76l1pQbkHOuFZRHKMOlGnvPFsnDNe8dEw6_7gFdj45okw--jZlmD6XZ_j03kUWiUDcLA0flkCJ6lLzmja1fEanRsbJp4S6v3CLJNHlEtiseHlaqv-ulA/w400-h58/RTSpecAn_Eq4.PNG" width="400" /></a></div><br /><p>The highest frequency component in the spectrum is also referred to as the <i>Nyquist </i>frequency. Since the sample rate for taking data is 1/𝛥T, the Nyquist frequency, the highest frequency for which we can calculate a sine wave component is one-half the sample rate. If the sample rate is 10 GS/s, the Nyquist frequency is 5 GHz.</p><p>The average value of an ideal sine wave is always 0. This means that when we use a collection of sine waves to describe a real waveform, the average value of the recreated time-domain waveform is always 0. But real waveforms have an average value, or DC offset. To account for this, we store the DC component in the 0 Hz frequency component, which is 0 x the fundamental. On most oscilloscopes, you can suppress plotting the 0th frequency component to zoom in on the scale of the display. </p><h3 style="text-align: left;">5. The FFT speeds calculation by truncating the buffer to 2^n sample points</h3><p>One million data points would involve about 1 trillion DFT calculations to create one spectrum. This make take longer to calculate than is convenient. To get around this problem, we use a much faster version of the DFT called the Fast Fourier Transform (FFT). It calculates the same integrals as the DFT, but it applies matrix math to perform the calculations using a total number of points that is a power of 2. If there are 1 million points in the buffer, the highest number of points that could be included in the FFT calculation would be 2^19 = 524,288 points. We throw out almost half the measured data to gain incredibly fast computation time.</p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4qzGUzrhJWc6kYT_BgavG2I-3qA5QItjDIEZKrCcyqf4Pq5OrpVlZGcMQ-mwpIQGiD3tmwfkpM505rnff-RMkGBg-NFXCUqBtbRk9oj0cWpOG1PBmP5zYfRmqgfoIFI5EgTg6RveGHjzgrhBabfJdlCGqa83BfzEYss-KRPNf56mFHdWqM-sNaUfZBw/s943/RTSpecAn_Fig2.PNG" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="525" data-original-width="943" height="178" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4qzGUzrhJWc6kYT_BgavG2I-3qA5QItjDIEZKrCcyqf4Pq5OrpVlZGcMQ-mwpIQGiD3tmwfkpM505rnff-RMkGBg-NFXCUqBtbRk9oj0cWpOG1PBmP5zYfRmqgfoIFI5EgTg6RveGHjzgrhBabfJdlCGqa83BfzEYss-KRPNf56mFHdWqM-sNaUfZBw/s320/RTSpecAn_Fig2.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2 Between the vertical dashed lines is the <br />region of the acquisition buffer that contains the <br />2^n points which will be used in the FFT.</span></td></tr></tbody></table>The first step in performing an FFT is to define the region of the acquisition buffer that contains the 2^n points that will be computed. Most oscilloscopes allow you to pick either the central region of the time-domain screen or a count from the left edge. Figure 2 shows the region that will be included in the FFT calculation highlighted on the screen.<p></p><p>When the acquisition buffer time is 1 µs, and we have 1 million points, we expect the fundamental to be 1 MHz. In the spectrum, the FFT acquisition buffer is smaller than this, which means the actual resolution is slightly larger than 1 MHz. But these estimates are still a good value to use when thinking about the features of the spectrum. </p><h3 style="text-align: left;">6. Windowing functions prevent spectral leakage due to the truncation</h3><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEioN01EPkQkHIU3PPVMzQxJPi5jix6guW79j6lFtl9gSARzgU9A9ytx_EUKy_vG2UTVrSIEbkAcJEObP_euOXeT_8Ly_XOByn9uKeCBrJu49FJX4kdP5c28ftVn9jA0Snbs69WYQYoOGPk_ppktrtC_lN5gMIpp3Q8R4MmKH8j5tP5BcukjFU0I-ftuug/s947/RTSpecAn_Fig3.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="266" data-original-width="947" height="90" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEioN01EPkQkHIU3PPVMzQxJPi5jix6guW79j6lFtl9gSARzgU9A9ytx_EUKy_vG2UTVrSIEbkAcJEObP_euOXeT_8Ly_XOByn9uKeCBrJu49FJX4kdP5c28ftVn9jA0Snbs69WYQYoOGPk_ppktrtC_lN5gMIpp3Q8R4MmKH8j5tP5BcukjFU0I-ftuug/s320/RTSpecAn_Fig3.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3. Example sine wave that does not have an<br />integral number of cycles in the acquisition buffer. <br />When appended, there is a discontinuity in the<br />waveform at each edge of the buffer. <br />Image courtesy National Instruments.</span></td></tr></tbody></table>To create a periodic waveform, we took the acquisition buffer and repeated it indefinitely. When using the FFT function, we further truncate the acquisition buffer and repeat the truncated buffer indefinitely. This means that at the boundaries of each appended acquisition buffer, there may be a discontinuity in the waveform corresponding to the end of one buffer and the beginning of the next one (Figure 3).<p></p><p>Normally, the spectrum of a sine wave that has an integral number of cycles in each buffer will have a single spike at its peak frequency. However, if the sine wave is artificially cut off due to the truncated acquisition buffer, the infinitely long waveform will now have a discontinuity that will force some of the frequency components from the peak frequency into adjacent frequency components, which can result in a distortion of the narrow peak.</p><p>This effect is called <i>spectral leakage</i>. It is an artifact of the discontinuity at the boundaries of the buffers due to the first voltage value not being the same as the last voltage value. The way to reduce this artifact is to artificially reduce the discontinuity by multiplying the entire acquisition buffer by a <i>window function</i>. This gradually forces the voltage value at the ends of the acquisition buffer to be 0, guaranteeing that the end of one buffer is continuous with the beginning of the next buffer. </p><p>There are a number of windowing functions commonly used. They differ in how much spectral leakage they allow and the resulting resolution. Unless you have a strong compelling reason, we recommend that you always use either the von Hann (sometimes called Hanning) or the Blackman-Harris function.</p><h3 style="text-align: left;">Analyzing Time Domain Waveforms in the Frequency Domain</h3><p>The value of spectral analysis is being able to identify the spectral “fingerprint” of repetitive signals with frequencies that fit within the range between the fundamental (1/acquisition buffer) and the Nyquist (½ x sample rate). Each time the oscilloscope measures a new acquisition buffer of time-domain voltages, the newly calculated spectral response is displayed. As periodic signals in the source change, their spectral fingerprint changes. </p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi8A0jqP2Qv5B-Z2QDuacxipzvUP3rNrID3K54eTw84dPiBVIUgN9yYHtBu0J05xHES8QHyLogltHZUYYrgBJd0X4GdmndOS4QOmSeVpfXSy7ie4snXhibHnTdUaO_7BZj-eoaH2GCjabeHfzSbHFSR6KjO1pKvcMx6KEQMGG9GOKu1MUfAkAg5U1LEbA/s933/RTSpecAn_Fig4.PNG" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="484" data-original-width="933" height="166" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi8A0jqP2Qv5B-Z2QDuacxipzvUP3rNrID3K54eTw84dPiBVIUgN9yYHtBu0J05xHES8QHyLogltHZUYYrgBJd0X4GdmndOS4QOmSeVpfXSy7ie4snXhibHnTdUaO_7BZj-eoaH2GCjabeHfzSbHFSR6KjO1pKvcMx6KEQMGG9GOKu1MUfAkAg5U1LEbA/s320/RTSpecAn_Fig4.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 4. The real-time spectrum of a SMPS output <br />while the output load is changing showing <br />the time variation of the peak frequencies.</span></td></tr></tbody></table>Any application where it might be helpful to identify periodic signals of a given frequency is a great candidate for real-time spectral analysis. The most common application is searching for the sources of interference on important signals. Figure 4 shows the spectral response of the output of a switch-mode power supply (SMPS) as its load was changed. The peaks at about 50 kHz, the switching frequency, change over time as the load changes, as shown by a spectrogram in the upper part of the figure. When you observe these frequency components in the noise of an amplifier or the jitter of an oscillator, you have an idea of a possible root cause. <p></p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXFhdxO4uxLnwOyz4rXDAYIa4frRMTL1h2yM3oBPbUw-88XYaACQFfRsMCGEYeYjA2kL1oSazFtBES9DXF3IdECNI3cwyTVLnr7wH9mYsacU6As3wFX6ACNCtkYHzUFdwAVqG-eEMWhqXnbRFBs8vHHo2Jcl4l-OCkMTyUr_zWZIPhJp69ZSOwwarN6A/s945/RTSpecAn_Fig5.PNG" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="483" data-original-width="945" height="164" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXFhdxO4uxLnwOyz4rXDAYIa4frRMTL1h2yM3oBPbUw-88XYaACQFfRsMCGEYeYjA2kL1oSazFtBES9DXF3IdECNI3cwyTVLnr7wH9mYsacU6As3wFX6ACNCtkYHzUFdwAVqG-eEMWhqXnbRFBs8vHHo2Jcl4l-OCkMTyUr_zWZIPhJp69ZSOwwarN6A/s320/RTSpecAn_Fig5.PNG" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 5. Measured real-time spectrum of the noise <br />from a USB power rail showing large components <br />in the FM radio band from pick up in the probe.</span></td></tr></tbody></table>When looking at the spectrum of RF interference, we can often pick up specific communications signals. Figure 5 shows the real-time spectrum of the power rail in a USB-powered device measured using a 10x probe with a large tip loop. The spectral fingerprint shows pick up in the FM radio band from 87 MHz to 108 MHz. <p></p><p>To learn more about this topic, view this free webinar by Prof. Eric Bogatin, <a href="https://go.teledynelecroy.com/l/48392/2021-06-04/87xtss?utm_source=Webinar&utm_medium=bethesignal-com-homepage&utm_content=+21-07-21+Bogatin+Spectral+Analysis+Webinar&utm_campaign=+21-07-21+Bogatin+Spectral+Analysis" target="_blank">Understanding Real-time Spectral Analysis</a>.</p><h4 style="text-align: left;">Also see:</h4><div><a href="https://blog.teledynelecroy.com/2021/02/using-spectrograms-to-visualize.html" target="_blank">Using Spectrograms to Visualize Spectral Changes</a></div><div><a href="https://blog.teledynelecroy.com/2021/02/situational-awareness-rf-noise-in-lab.html" target="_blank">Situational Awareness: RF Noise in the Lab</a></div><div><a href="https://blog.teledynelecroy.com/2019/05/a-real-world-fft-example.html" target="_blank">A Real World FFT Example</a></div><div><a href="https://blog.teledynelecroy.com/2019/04/fast-fourier-transforms-automatic.html" target="_blank">Fast Fourier Transforms: Automatic Edition</a></div><div><a href="https://blog.teledynelecroy.com/2019/04/fast-fourier-transforms-stickshift.html" target="_blank">Fast Fourier Transforms: Stickshift Edition</a></div><div><a href="https://blog.teledynelecroy.com/2019/01/getting-from-time-domain-to-frequency.html">Getting From the Time Domain to the Frequency Domain</a><br /><a href="https://blog.teledynelecroy.com/2019/02/about-data-truncation-in-fast-fourier.html">About Data Truncation in Fast Fourier Transforms</a><br /><div><a href="https://blog.teledynelecroy.com/2019/02/about-windowing-in-fast-fourier.html"><span id="goog_76692086"></span>About Windowing in Fast Fourier Transforms</a><br /><a href="https://blog.teledynelecroy.com/2019/03/which-windowing-function-to-use-in-ffts.html">Which Windowing Function to Use in FFTs?</a></div></div><div><br /></div><div><br /></div><div><br /></div><div><br /></div><p><br /></p><p><br /></p><p><br /></p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-2179841618451334547.post-6461046907895726272022-07-05T08:00:00.020-04:002022-08-09T14:22:34.325-04:00 A Tale of Two Calibrations: Vector Network Analyzer vs. WavePulser 40iX<p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgE4AJ2J2tW46VSlCggbQDb7FXjGSTiZT8HLjn0wBBmJdTHir2YLb0DW22Z5buDi2kmTRrgRDoCLQl9tX4Wv-9LEwVAaA5CQXDFxuZKj-XNyFsIothzCZwZOaaTzwNW3bynkirjT585RD5EclZ_waiq7IaTHM0Ma5e3LwHTdt3IoMWL9PWT3bex3huKDw/s1726/VNACal_Fig1.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1726" data-original-width="1207" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgE4AJ2J2tW46VSlCggbQDb7FXjGSTiZT8HLjn0wBBmJdTHir2YLb0DW22Z5buDi2kmTRrgRDoCLQl9tX4Wv-9LEwVAaA5CQXDFxuZKj-XNyFsIothzCZwZOaaTzwNW3bynkirjT585RD5EclZ_waiq7IaTHM0Ma5e3LwHTdt3IoMWL9PWT3bex3huKDw/s320/VNACal_Fig1.png" width="224" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 1: This sequence diagram of the <br />classic SOLT 2-path calibration shows <br />the order of connections required. </span></td></tr></tbody></table>It was the best of S-parameter measurements, it was the worst of S-parameter measurements…and the difference was in the calibration. Calibrating a vector network analyzer (VNA) before making any measurements is required in order to reduce errors from imperfect channel matching, less than optimal directivity in the directional couplers and cable response issues. While VNAs are precisely calibrated at the factory, that calibration only extends to the front panel measurement ports. There will inevitably be drift on the internal paths over time. Also, any cables, adaptors or fixtures connected to the measurement ports must be characterized and de-embedded in order to make exact measurements of the device under test (DUT). <p></p><p>There are many possible calibration methods depending on the number of ports and paths being measured. For simplicity, let’s consider the common 2-port, 2-path calibration. This calibration method will yield a full set of S-parameters for the two ports: S11, S12, S21 and S22. It requires the use of a short, open, load and through (SOLT) calibration reference standard, along with the cables used in the test setup, as shown in Figure 1.<span></span></p><a name='more'></a><p></p><p>The diagram shows the sequence of connections made from the SOLT standard to the VNA for calibrations before the final connection of the DUT. Both ports are connected to a short, an open, a load (normally 50 Ohms) and a through path in sequence, and a measurement is taken. The large number of manual connections (at least 10 for a 2-port measurement) takes time and creates opportunity for error due to improper connections. </p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhufbGjKKTL8OJ5xdu6oSf5OyPbakuFS1Un65-R5SdqBUIRA5ApXQpm-gZxgTcGz7Z_sf-fu_6Lsyr0qe1rzD4uQxOISvjKDqa1Xc6KwvzG_Tfr1Hsuze1SkZbmu4MNnZDkZVCBj8vnQ4ZiL1w_ezUmb9KeB3DJE0C7glH3ldsUJHpCn__gMymFLOC0GQ/s1207/VNACal_Fig2.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="820" data-original-width="1207" height="136" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhufbGjKKTL8OJ5xdu6oSf5OyPbakuFS1Un65-R5SdqBUIRA5ApXQpm-gZxgTcGz7Z_sf-fu_6Lsyr0qe1rzD4uQxOISvjKDqa1Xc6KwvzG_Tfr1Hsuze1SkZbmu4MNnZDkZVCBj8vnQ4ZiL1w_ezUmb9KeB3DJE0C7glH3ldsUJHpCn__gMymFLOC0GQ/w200-h136/VNACal_Fig2.png" width="200" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 2: ECAL modules simplify the <br />VNA calibration process by reducing the<br />number of manual connections required.</span></td></tr></tbody></table>In order to simplify this calibration process, some VNA manufacturers have designed electronic calibration (ECAL) systems that combine all the SOLT standards into single package controlled by a computer or the VNA itself. This reduces the number of connections that must be made for the SOLT calibration, as shown in Figure 2.<p></p><p>The ECAL module is connected only once, reducing the number of connections significantly, and the calibration process is now semi-automated, which reduces the total calibration time. However, ECAL modules are expensive “add ons” to the VNA, already quite an expensive instrument.</p><p>Compare this to calibration for the Teledyne LeCroy <a href="https://teledynelecroy.com/wavepulser" target="_blank">WavePulser 40iX</a>. The WavePulser 40iX is a 2- or 4-port TDR instrument specifically designed for high-speed analysis of interconnects in serial data cables, channels, connectors, vias, backplanes, PCBs and ICs. The WavePulser uses an innovative, automatic calibration process that results in faster and easier measurements. The internal calibration structure of the WavePulser is illustrated in Figure 3.</p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEisUDve532J0F7fcj_7nudFGhSZTSLO0cF78_9i1wYKBMKSqRg5ti9qKPAWXGfsaM1HXvioJ9GisAWtAgTcGy9UBeRs5IiPzxwy8kXTVQWjhfUTQC8QalMG4J7AZIORqRSvWDBpuqLGXQ8saxXS8vgXbz7ckVB1sxtR7bs88wILAIOPdohzucfSfUycgQ/s1032/VNACal_Fig3.png" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="840" data-original-width="1032" height="325" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEisUDve532J0F7fcj_7nudFGhSZTSLO0cF78_9i1wYKBMKSqRg5ti9qKPAWXGfsaM1HXvioJ9GisAWtAgTcGy9UBeRs5IiPzxwy8kXTVQWjhfUTQC8QalMG4J7AZIORqRSvWDBpuqLGXQ8saxXS8vgXbz7ckVB1sxtR7bs88wILAIOPdohzucfSfUycgQ/w400-h325/VNACal_Fig3.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Figure 3: The WavePulser 40iX uses internal relays to step through <br />the SOLT standards for each port during the automatic calibration.</span></td></tr></tbody></table>The pulser/samplers of the WavePulser are connected to single-pole, 6-throw (SP6T) relays. The relay outputs connect to the internal short, open and load calibration standards. They also connect to the other port(s) implementing the through connection required during calibration. One of the relay outputs connects to the bulkhead output connector on the front panel—this is the<i> instrument reference plane</i>. This entire calibration subassembly is factory calibrated by making S-parameter measurements of each path from DC to 40 GHz. The cables matched to these ports are also characterized and marked with unique serial numbers. The S-parameters for the cables are part of the factory calibration and are automatically de-embedded every measurement to move the <i>measurement reference plane</i> to the point of connection to the DUT. Tools are included for de-embedding any other adapters or fixtures.<p></p><p>When you want to make a measurement, the DUT is connected to the cables matched to Port 1 and Port 2, and the WavePulser is powered on and allowed to reach its operating temperature. When the measurement is started, the instrument calibrates itself by alternately switching the relays through the short, open, load and through standards, obtaining a set of raw S-parameters. Two acquisitions are made: one with the Port 1 pulser active and the other with the Port 2 pulser active. These raw values are combined with the factory-measured values of the standards using traditional calibration algorithms to yield measurements corrected to the measurement reference plane. After being corrected by the stored calibration parameters, a calibrated measurement of the DUT is obtained. All this occurs automatically with only the DUT having to be connected once, quite an improvement over the traditional SOLT calibration. It is even simpler than the ECAL calibration, which still requires connecting to the external ECAL module before connecting the DUT.</p><p>The WavePulser 40iX also allows for alternative manual user calibrations and includes a calibration kit for this purpose. The automatic calibration calibrates to the internal reference plane then de-embeds the remainder of the output path, including the cables. The cables can change over time, especially due to mechanical flexure. A manual calibration corrects for any of these changes. </p><p>The WavePulser also supports a user second-tier calibration that dovetails with the automatic calibration to produce even greater accuracy. An application note available on the Teledyne LeCroy website, “<a href="https://teledynelecroy.com/doc/second-tier-calibration" target="_blank">WavePulser 40iX Second Tier Calibration</a>”, provides more information about the user second-tier calibration.</p><p>The WavePulser 40iX calibration is automated, simple and fast. Just connect cables to the DUT, then press “Go”. It does not require the purchase of additional external calibration standards or a laborious calibration process.</p><h4 style="text-align: left;">See also:</h4><p><a href="https://blog.teledynelecroy.com/2022/03/when-you-need-tdr-and-when-you-need.html" target="_blank">When You Need a TDR and When You Need a WavePulser</a></p><p><a href="https://blog.teledynelecroy.com/2021/06/automotive-ethernet-mdi-s-parameter.html" target="_blank">Automotive Ethernet MDI S-Parameter Testing</a></p><p><br /></p><p><br /></p><p><br /></p>Unknownnoreply@blogger.com0