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dncmrc1's avatar
dncmrc1
Icon for Occasional Contributor rankOccasional Contributor
11 days ago
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Arria 10 GX RX max intra-differential pair skew

I would like to know, in the Arria 10 GX, what is the RX transceiver max allowed intra-differential pair skew.

If it is rate-dependent (as likely is) please let me know all the characterized values.

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  • FvM's avatar
    FvM
    2 days ago

    Hi,

    I presume that tolerated maximal intra pair skew is larger than guessed numbers. I see specification of up to 0.4 Tbit skew in HDMI 1.4 spec, expect that Arria 10 transceiver has no problem to decode the signal.

    As far as I understand, Altera doesn't specify RX max intra pair skew. I also don't think that intra pair skew is a primary parameter in receiver  performance analysis. It translates into differential mode pulse distortion and unwanted common mode signal. Related to specified receiver parameters, minimal eye opening is the nearest relevant parameter.

    To determine HDMI compliance, I would either model expected input waveform with maximal skew and check eye opening. Or test receiver performance in real hardware.

    Regards Frank

5 Replies

  • Ash_R_Intel's avatar
    Ash_R_Intel
    Icon for Regular Contributor rankRegular Contributor
    8 days ago

    Hi,

    Altera does not publish any numbers for the Rx intra-pair skew. We generally recommend to follow the layout guidelines, perform SI simulations to check for the eye opening, BER failure etc.

    In my opinion, it is a function of data rate and board level parameters. As a general practice, people generally follow below rule:

    For <= 6 Gbps, <= 10ps

    For >10 Gbps, <= 3ps to 5ps

     

    Regards

  • dncmrc1's avatar
    dncmrc1
    Icon for Occasional Contributor rankOccasional Contributor
    7 days ago

    Hi,

    This is not about layout.

    The Arria 10 RX transceiver is used to implement an HDMI receiver. HDMI PHY compliance test will apply a signal to the Arria 10 RX with a certain intra-pair skew and the RX must be able to receive this signal.

    If it isn't, it means you cannot build an HDMI RX using an Arria 10. This is why I am asking here, what is the max intra-pair skew the Arria 10 RX can take?

    Regards

    • Ash_R_Intel's avatar
      Ash_R_Intel
      Icon for Regular Contributor rankRegular Contributor
      3 days ago

      Hi,

      As I mentioned before, Altera does not publish this data. The Rx uses the adaptation to capture a reliable data, but it does rely on the minimum skew between P and N pins. Recommend to keep value under < 5ps as a general practice.

       

      Regards

  • dncmrc1's avatar
    dncmrc1
    Icon for Occasional Contributor rankOccasional Contributor
    2 days ago

    Hi,

    To pass HDMI PHY compliance, for instance at 3G rate the RX must be able to function with 80 ps of intra-lane skew. As you can see, your 5 ps figure cannot be correct, otherwise the Arria 10 RX would not be usable to implement an HDMI receiver.

    Comments?

  • FvM's avatar
    FvM
    Icon for Super Contributor rankSuper Contributor
    2 days ago

    Hi,

    I presume that tolerated maximal intra pair skew is larger than guessed numbers. I see specification of up to 0.4 Tbit skew in HDMI 1.4 spec, expect that Arria 10 transceiver has no problem to decode the signal.

    As far as I understand, Altera doesn't specify RX max intra pair skew. I also don't think that intra pair skew is a primary parameter in receiver  performance analysis. It translates into differential mode pulse distortion and unwanted common mode signal. Related to specified receiver parameters, minimal eye opening is the nearest relevant parameter.

    To determine HDMI compliance, I would either model expected input waveform with maximal skew and check eye opening. Or test receiver performance in real hardware.

    Regards Frank