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TUSB501 / output swing amplitude

K.Yaita
Guru 29690 points
Other Parts Discussed in Thread: TUSB501

Hi Team,

I would like to ask 2 questions.

1)
The datasheet shows output swing amplitude is 930mVpp(TYP) when OS=Low.
Does it mean TUSB501 output 930mVpp(TYP) when input differential voltage is 100mV～1200mVpp?




2)
My customer saw the following eye diagram at TUSB501 input (RXP, RXN) but it seems output swing amplitude of TUSB501 is lower than 930mVpp.
Is there any concern about the issue?



Best Regards,
Yaita / Japan disty

  • 0
    TI__Mastermind 36085 points
    Hello,

    I need to validate the information on the datasheet, so I can provide a feedback regarding the inconsistency. Regarding the eye diagram; the output is quite lower. I would like to see the input eye diagram, as well as the configuration on the TUSB501, also please verify that VCC is within the recommended operating conditions.

    Best regards,
    Diego.
  • 0 in reply to Diego Cortes
    Guru 29690 points

    Hi Diego-san,

    Thank you for your quick reply.

    I am looking forward to your feedback regarding question (1).

    Regarding question (2), the eye diagram I attatched was input diagram.
    It shows more than 100mVpp, but I heard output swing amplitude is lower than 930mVpp.
    He said output swing amplitude was about 600mVpp.

    I will confirm the configuration and VCC voltage, then feedback to you.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 36085 points
    Hello Yaita-san,

    The output depends on the input. It may be caused by a wrong EQ setting. Please provide the channel information (trace length & material for the input and output channel), as well as the implemented settings.

    Best regards,
    Diego.
  • 0 in reply to Diego Cortes
    Guru 29690 points

    Hi Diego-san,

    I apologoze for late reply.
    Regarding question (2), I heard the channel information as the following from my customer.
    -input: 164mm trace length of PCB
    -output: 20mm length of strap + connector
    *CPU - PCB(164mm) - TUSB501 - strap(20mm) - connector

    However, he wants to know about question (1) preferentially.
    Do you have update?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 36085 points
    Hello Yaita-san,

    Regarding the question 1: The TUSB501 recovers the input and re-transmits according the configured output configuration, so it is possible to have the case that you mentioned in a first instance.

    I would like to see the layout design, seems that the customer has a lot of loss in a relatively short trace. Typically I would suggest the an EQ=3 or 6, but in this case the loss is higher than the expected. Please provide the layout files to diego.cortes@ti.com, so I can review the design.

    Regards,
    Diego.
  • 0 in reply to Diego Cortes
    Guru 29690 points

    Diego-san,

    Thank you for your continuous support.

    Regarding the question 1:
    Could you tell me the input condition to output 930mVpp(OS=Low)?
    Does the following indicate that output differential voltage(the transition bit) shows 930mV under any amplitude of input differential voltage swing? 



    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 36085 points
    Hello Yaita-san,

    The amplitude should be > 100mv, however the input signal that you posted has a lot of skew, as you can see the eye diagram looks kind of twisted. That's why I would like to review the layout. The differential pairs may be mismatched.

    Regards,
    Diego.
  • 0 in reply to Diego Cortes
    Guru 29690 points

    Hi Diego-san,

    Thank you for your explanation.
    I understood about question (1).

    Regarding layout check, I will talk with my customer and ask you if he needed.
    I appreciate for your kind and continuous support.

    Best Regards,
    Yaita