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TUSB2077A: layout guide

Shu-Cheng LIN
Guru 11785 points
Part Number: TUSB2077A

Hi Sirs,

Sorry to bother you.

Below is the TUSB2077APT layout guide
"7. Match the etch lengths of the differential pair traces. The USB 2.0 differential pairs should not exceed 50 mils relative trace length difference."

But our shape is long, the  best location is in the board
Is it closer to the USB connector?
It seems a bit unreasonable,
Please help confirm
Thank you

  • 0
    TI__Guru**** 177301 points
    Shu-Cheng

    This is the skew between DP and DM, The maximum recommended trace length for USB 2.0 differential pair signals is 8 inches. Is this an issue?

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 11785 points

    Hi Sirs,

    Thanks for your reply.

    About 7. Match the etch lengths of the differential pair traces. The USB 2.0 differential pairs should not exceed 50 mils relative trace length difference.”

    We think the narrative should not be between DP and DM, it's should be the trace length of each port and port

    Of course, the length of 8 inches will not cause layout troubles.
    But the relative length on the winding of the port and port will be.
    So I want to know if I misunderstood??
    Could you help me confirm this item??

  • 0 in reply to Shu-Cheng LIN
    TI__Guru**** 177301 points
    Shu-Cheng

    Each downstream port is independent from each other.

    Bullet #6 of section 11 gives the total trace length requirement, which is max 8in.

    Bullet #7 of section 11 is the skew between DP and DP for each port, which is max 50mil.

    50mil is not between port to port.

    Thanks
    David