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Original question:

TUSB1064: AUX signal eye diagram was decreased due to TUSB1064

TUSB1064: TUSB1064: AUX signal eye diagram was decreased due to TUSB1064

nakanishi.yoshifumi
Prodigy 30 points
Part Number: TUSB1064

David-san

 sorry to have kept for a long time.

I tried to check the swing level by differential probe again by using several laptop and desktop.

when I measure again it,

the swing level after TUSB1064 was increased.

I'm not sure what is happen.

do you have any comment why increase the swing level after go through TUSB1064 although the reuslt was changed from last time checking result ?

I'd like to know what is happen and whether the result is valid or not.

[Problem] decrease the swing of AUX after pass through TUSB1064_rev5.pptx

Best Regards,

Y.Nakanishi

  • 0
    TI__Guru**** 156171 points

    Y.Nakanishi

    I honestly don't know. The TUSB1064 AUX/SBU is a passive switch only and does not provide any SWING control. I wonder if the probe input resistance with the external pullup/pulldown on AUX is creating a signal amplitude distortion and changes in DC bias conditions, therefore affect your measurement result.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 30 points

    David-san

     thank you for your quickly reply.

    I see.

    in this case, I better to measure the passive probe to see the waveform against GND ? ( so called single probe is better ? )
    because, I'm very sorry, although you provide adivce to me to use single probe, I still checked by differential probe so far....

    According to your advice,

    the DC level to input to TUSB1064 is very important.

    I understand that I have to measure by single probe.

    is my understanding correct ?

    Best Regards,

    Y.Nakanishi

  • 0 in reply to nakanishi.yoshifumi
    TI__Guru**** 156171 points

    Y.Nakanishi-san

    You have to make sure the AUXP/N and SBU1/2 common mode voltage are within TUSB1064 spec as shown below, otherwise the AUX data will not go through the TUSB1064 AUX/SBU switch.

    To measure the waveform, you want to use high impedance single ended or differential probe so minimize the impact of the probe on the measurement result. 

    Do you have a link training log file that you can share? You said link training failed sometimes, how did you determine it is related to the AUX signal amplitude? If I look at the measurement result itself, it is above the DP spec of AUX peak-to-peak voltage received by Main-Link
    Sink at TP3 minimum 270mV.

    Thanks

    David