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WEBENCH Interface Designer - OUT_PT1 waveform

Kawai
Guru 19775 points

Hi Team,

Please allow me to ask you about Webench Interface designer.

What is the definition for "OUT_PT1" waveform ? I could not understand which part of the device Webench is simulating. From the simulation result, OUT_PT1 has a better waveform than SC_IN, however still has closed eye. SC_OUT has a clear open eye.

I couldn't find the document or user's guide for Webench Interface Designer. Could you please explain us what OUT_PT1 is ?

Best Regards,

Kawai

  • 0
    TI__Mastermind 29655 points
    Hi Kawai-san,

    In the Webench Interface Designer tool, the OUT_PT1 eye probe is the measurement of the signal AFTER it passes through the Rx components before any retiming occurs. For the retimer, this involves the signal conditioning effects of the Rx CTLE and DFE, which are before the input to the decision slicer. The SC_OUT eye probe is then the eye after CDR and Tx FIR Equalization, such as De-emphasis. I tried simulating the same situation you showed in the screenshot, and it shows that at SC_OUT, the waveform has been cleaned up significantly.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 19775 points
    Hi Michael-san,

    Thanks for your support.
    I understood that OUT_PT1 is the waveform before the CDR for DSxxxDFxxx family devices. However, looking at the waveform of OUT_PT1, it doesn't have an open eye. Can the CDR receive this signal ? I was wondering if this is a correct result.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Mastermind 29655 points
    Hi Kawai-san,

    The CDR is capable of receiving a completely closed eye and outputting what appears to be a clean output. However, since the retimer's CDR uses a slicer to make a decision about whether the incoming signal is a "1" or "0", there is no guarantee that the decision the CDR makes is correct. In other words, even though there is a clean output from the retimer Tx, that does not necessarily mean that the link is error-free. Therefore, to ensure the result is error-free, the eye before the CDR should be as open as possible, and in a realistic test scenario, a BERT should be used.

    Try playing with the CTLE settings on the retimer to determine whether you can open the eye more.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 19775 points
    Michale-san, thank you for the information.

    Best Regards,
    Kawai