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    SERDES termination methods

    Hello all,

    I have a question about the SERDES terminations methods. In the DDR world, we have different termination specs for LPDDR, DDR3(SSTL), DDR4/5(POD).
    Is this the same story in SERDES world? Are PCIe, SATA,XAUI, etc having different terminations? Where can i find the summary of those termination methods?

    Thank you!

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    Re: SERDES termination methods

    Why not review the respective standards? In a short, they are all using 100 ohm differential termination.



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    Re: SERDES termination methods

    Quote Originally Posted by FvM View Post
    Why not review the respective standards? In a short, they are all using 100 ohm differential termination.
    Hello FvM,

    Yes. I wanted to do that. However I'm not familiar with SERDES standard organizations and document. I know I can get DDR4/5 standards from JEDEC website.
    How do I find SERDES standards? If you can point me one, that will be very helpful.

    Thank you!



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    Re: SERDES termination methods

    Hi,

    A simple internet search will do.
    Or wikipedia...
    Or a search for application notes on any SERDES IC manufacturer..
    Or...

    Klaus
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    Re: SERDES termination methods

    If you are looking for the standard. SERDES uses CML or Current Mode Logic. The term SERDES describes the upper layer protocol for the Serilaizer and Deserializer.

    You can have SERDES that uses some other differential standard like LVDS, but the majority of high speed mulit-Gb type interfaces use CML.



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    Re: SERDES termination methods

    Thank you all. Please understand my newbie questions.

    I think this is a reasonable document to look at
    https://www.xilinx.com/support/docum...ansceivers.pdf

    It seems the termination method changes based on the protocols.



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    Re: SERDES termination methods

    Hi,

    It seems the termination method changes based on the protocols.
    Never heard that termination depends on protocol. In my eyes this makes no sense.
    I've just tried to find this information in the given document. Which page are you referring to?

    Klaus
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    Re: SERDES termination methods

    Quote Originally Posted by KlausST View Post
    Hi,


    Never heard that termination depends on protocol. In my eyes this makes no sense.
    I've just tried to find this information in the given document. Which page are you referring to?

    Klaus
    Klaus. You are right. I was looking at different pdf.

    https://www.xilinx.com/support/docum...ansceivers.pdf

    Yes. termination didn't change. The termination voltage changed. Again, I'm not a SERDES expert. I just want to learn.



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    Re: SERDES termination methods

    I noticed some products have a option to have external or internal capacitive coupling. Is it because of the bandwidth limit?



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    Re: SERDES termination methods

    Hi,

    Often capacitive coupling is used to suppress DC current ... useful if you want to drive an isolating transformer.

    Klaus
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