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DS80PCI102: AC-cap placement of DS80PCI102

Shenhua Zhang
Prodigy 640 points
Part Number: DS80PCI102


Hi expert,

I’m writing to consult you the AC-coupling capacitor placement of DS80PCI102.

Today customer reviewed a board and found the placement of ac-coupling cap is confusing. Below figure displays the structure.

The spec of DS80PCI102 shows the ac-cap should be needed on both Tx and Rx lane. Would you please help to check it whether below structure works in case customer missed any important inform?

  • 0
    TI__Mastermind 43795 points

    Hi Shenhua,

    This is not a typical placement.  Having two series AC coupling capacitors is not optimal, but we have not seen an issue when this occurs.

    Is the CPU and DS80PCI102 on the same PCB?  Usually the Tx pins on the CPU motherboard have an AC coupling capacitor in the path.

    If there is no AC coupling between the CPU and the DS80PCI102 there will be some interoperation issues.  The DS80PCI102 pulls the input common mode to 2.5V when the terminations are active.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    TI__Mastermind 43795 points

    Hi Shenhua,

    Let us know if there are some updates by starting a new thread.  I'm closing this tread for now.

    Regards,

    Lee