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TUSB564RNQEVM: Should AC coupling capacitors be used RX1P/N and RX2P/N

James turner
Prodigy 60 points
Part Number: TUSB564RNQEVM
Other Parts Discussed in Thread: TUSB564

The TUSB564 EVM schematic shows 470nF AC coupling capacitors connected to the RX1P/N and RX2P/N pins, but the datasheet show that no AC coupling capacitors are connected on this path. The TUSB1046 Eval board schematic and design also show that no AC coupling capacitors are connected to the RX1P/N and RX2P/N pins. Which implementation is correct?

  • 0
    TI__Guru*** 139515 points
    James

    The AC coupling capacitors on RX lines are optional per the USB-IF ECN.

    This capacitor is useful for ESD/EOS protection and remove unwanted bias level from Rx side. Because RX side of different UBS-SS system have variable common mode voltage (use different termination scheme), this option can remove unmatched bias level for interconnection logic. After adding this capacitor leakage current through RX pin can be ideally 0mA and it is helpful to prevent water corrosion. (Same as TX side).

    The recommended value is 330nF.

    Thanks
    David