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SN65DP141: Question about how to calculate trace length

Austin Do
Expert 3275 points
Part Number: SN65DP141

Tool/software:

Hello team,

My customer has a question about trace length between output of DP141 and connector.

  • Speed:3G~4Gbps (FHP/60Hz)
  • Impedance: 85ohm.

In this case, what is the maximum trace length between output of DP141 and connector? Or is there a rule or calculation for this? I found that 2 inch is recommended, but I want to understand in detailed for this specific condition.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/957463/sn65dp141-trace-length?tisearch=e2e-sitesearch&keymatch=SN65DP141%252520AND%252520trace%252520AND%252520length# 

Thank you.

Best Regards,

Austin

  • 0
    TI__Expert 3275 points

    I would like to modify the speed.

    The speed should be HBR, 2 Lane(2.7 Gbps/lane)

    Best,

    Austin

  • +1 in reply to Austin Do
    TI__Mastermind 38385 points

    Hi Austin,

    The reason you want to keep the trace length <2 inch is due to the fact that the SN65DP141 is a linear redriver.

    This means that this redriver only applies an equalization function to the incoming signal and has no TX drive capabilities. A linear redriver is only able to compensate on the RX end. A limited redriver/ retimer is able to compensate for the TX and the RX. This is why you are able to drive longer distances with that kind of part. 

    If you are able to provide the layout or block diagram with planned trace lengths I will be able to provide a more tailored maximum trace length.

    The best way to implement a linear redriver on a source is to have it as close to the connector as possible so it can account for the optimum amount of loss on the RX side.