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TLK2711-SP: Matching transmit path lengths and impedances

Michael Bolt46
Prodigy 90 points
Part Number: TLK2711-SP

I am using the TLK2711-SP.

Unfortunately, I have an open-circuit track on one of the Tx differential tracks internal to my pcb, and would like to repair it instead of scrapping the board.

How practical is it to repair the board with an external wire link?

We have processes for the repair, it's getting the required performance afterwards is the issue.

How closely do I need to match the path lengths and impedances between the 2 differential tracks?

I am operating at 80 MHz clock, so a 1.6 Gbps raw data rate.

Many thanks

Michael

  • 0
    TI__Guru 62930 points
    Michael,
    This is not something that we would have characterized.
    Typically length matching should be within a few mils for matched pairs.
    Likely worse case is the impedance mismatch (vs length mismatch). I do not have good feel for how bad this would impact the link. Not sure what media you will be using? Blue wire, or adding shielded coax? The latter would be better.
    You may try to simulate to get an idea if the it will drastically impact your eye. There are IBIS models that should be sufficient showing the degradation with and without the repair.
    Another factor, is how robust the link is in the first place. There are many parameters that impact the robustness of the link and ultimately the amount of jitter. GTX_CLK clock (both TX and RX), clock ppm matching, jitter, VDD noise, cable media, impedance matching.

    Hopefully this helps.
    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade