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[FAQ] TUSB1002A: [FAQ] Purpose of the 330nF capacitors for the USB connector to the SuperSpeed RX and is it required?

David (ASIC) Liu
Guru**** 161366 points
Part Number: TUSB1002A

Tool/software:

What is the purpose of the 330nF capacitors on the SuperSpeed RX and is it required?

  • +1
    TI__Guru**** 161366 points

    Hi,

    Please see attached USB.org ECN on the optional 330nF for the SuperSpeed RX pins.

    5684.USB 3.1 ECN Rx AC Coupling Capacitor Option.pdf

    There are three implementation options for USB connector to the SuperSpeed RX pins:

    1. DC couple the  RX pins to USB connector. No 330nF capacitors and no 220kΩ pulldown resistors.

    2. 330nF capacitors with 220kΩ resistors pulldown resistors. The purpose of 220kΩ resistors is to discharge the capacitor within 250ms after a USB device is removed from the USB connector.

    3. The stub from the 220kΩ resistor pad may create impedance discontinuities causing negative impact to performance. Assuming leakage current from external components is enough to discharge capacitor, 330nF capacitor without the 220kΩ resistor is a valid option.

    Thanks

    David