# Ask Me Anything with Eric Bogatin **URL:** \ **Category:** Ask Me Anything\ **Tags:** signal-integrity, transmission-line, controlled-impedance\ **Created:** [November 18, 2023, 12:18am UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506 "2023-11-18T00:18:49Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:36pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/45 "2023-12-01T18:36:42Z")
Above 10 GHz, surface rounghness can more than double conductor loss. This is 20 Gbps. For \> 15 Gbps definitely consider the copper roughness and using low loss laminates. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:37pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/46 "2023-12-01T18:37:59Z")
It doesn’t. Stub resonances are stub resonance. The resonant frequency depends on the length of the stub and the Dk of the laminate. Keep stubs short regardless of the materials used. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:39pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/47 "2023-12-01T18:39:31Z")
all the usual methods: use low loss laminates, keep traces short, use wide traces, use smooth copper. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:41pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/48 "2023-12-01T18:41:05Z")
I think the impedance of the paths is more important than a target impedance in the frequency domain. Using controlled impedance interconnects is more about keeping the cross-talk low. If you need controlled impedance traces, use the same methods as in signal integrity. see my book on Signal and Power integrity simplified. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:41pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/49 "2023-12-01T18:41:32Z")
Sorry- I am not as familiar with rf testing methods. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:42pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/50 "2023-12-01T18:42:04Z")
sorry, don’t know. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:42pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/51 "2023-12-01T18:42:27Z")
no idea what you are referring to. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:43pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/52 "2023-12-01T18:43:23Z")
a rough rule of thumb is a trace length in inches equal to the rise time of the signal in nsec. For a 1 nsec rise time signal, traces shorter than 1 inch do not need termination. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:44pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/53 "2023-12-01T18:44:10Z")
Yes. Terminate a different pair in its differential impedance. terminate a signal-ended line it is characteristic impedance. read my book on signal integrity. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:44pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/54 "2023-12-01T18:44:38Z")
use SMT resistors or on-die resistors. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:46pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/55 "2023-12-01T18:46:08Z")
Not on boards with return planes. [see this article](https://www.signalintegrityjournal.com/blogs/4-eric-bogatin-signal-integrity-journal-technical-editor/post/402-pop-quiz-use-tight-or-loosely-coupled-differential-pairs-to-reduce-cross-talk) ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:46pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/56 "2023-12-01T18:46:47Z")
same methods as digital boards. Just manage the cross talk with signal spacing. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:51pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/57 "2023-12-01T18:51:02Z")
keep the two lines that make up the differential pair symmetric. This means same length and same cross section. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:52pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/58 "2023-12-01T18:52:24Z")
two most important terms are the vertical collapse or eye height opening and the horizontal collapse which is jitter. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 1, 2023, 6:53pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/59 "2023-12-01T18:53:25Z")
I use Ansys electronic desktop, Hyperlynx, ADS and Polar ---
**Author:** ![jeremie.waller](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jeremie.waller](https://sierraconnect.protoexpress.com/u/jeremie.waller)\ **Post date:** [December 1, 2023, 7:19pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/60 "2023-12-01T19:19:01Z")
Do you have a course curriculum designed around this book? The local university and trade college is interested in adding some courses on the subject as there currently are none. I’d love to chat some with you if you’re willing to share some advice on setting up some introductory and intermediate courses on PCB design. ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 2, 2023, 3:06pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/61 "2023-12-02T15:06:15Z")
contact me off line to discuss: eric.bogatin@colorado.edu ---
**Author:** ![eric.bogatin](https://sea2.discourse-cdn.com/sierraconnect/user_avatar/sierraconnect.protoexpress.com/eric.bogatin/32/186_2.png) [@eric.bogatin](https://sierraconnect.protoexpress.com/u/eric.bogatin)\ **Post date:** [December 2, 2023, 3:09pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/62 "2023-12-02T15:09:14Z")
A good place to start is my textbook on prototype design. I am working on posting a series of videos related to the labs I have created. Send me a direct email note to discuss this further. –eric ---
**Author:** ![guillermo](https://avatars.discourse-cdn.com/v4/letter/g/eb8c5e/32.png) [@guillermo](https://sierraconnect.protoexpress.com/u/guillermo)\ **Post date:** [December 2, 2023, 5:46pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/63 "2023-12-02T17:46:07Z")
Thanks for the answer Eric. The reason why I ask this question is because my products are not avionics instrumentation and do not interact with any of that, but are designed to operate other systems in the aircraft and they power from the standard 28V available in the aircraft. ---
**Author:** ![JimJJewett](https://avatars.discourse-cdn.com/v4/letter/j/d78d45/32.png) [@JimJJewett](https://sierraconnect.protoexpress.com/u/JimJJewett)\ **Post date:** [April 4, 2024, 6:27pm UTC](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506/64 "2024-04-04T18:27:47Z")
I love this rule of thumb! But it implies that a rise time in microseconds won’t need termination on a single board, let alone on a single chip. Until recent speeds, was termination theory mostly about not knowing how long the transmission line might be? [Previous page](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506.md?page=2) [Next page](https://sierraconnect.protoexpress.com/t/ask-me-anything-with-eric-bogatin/506.md?page=4)