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TUSB1002A: Removing the AC coupling capacitor & optional resistors

David Huang
Intellectual 2285 points

Part Number: TUSB1002A

Hi Team

For the TUSB1002A they are evaluating now the ds 8.2.2 Detailed Design Procedure says that C12,C13,R15,R16 are optional, will removing these bring any difference regarding the performance?

The type a connector transmitter should have AC coupling capacitor already so removing those capacitor would bring no influence at all, is my understanding correct?

Regards

  • 0
    TI__Guru**** 184461 points

    Hi,

    Hi,

    For C12, C13, please see attached ECN from USB.org. The capacitors are there for ESD/EOS protection and remove unwanted bias level from Rx side.

    5226.USB 3.1 ECN Rx AC Coupling Capacitor Option.pdf

    The additional resistors help to further reduce the discharge time to be well within the spec limit of 250 ms. As stated in the TUSB1002A these resistors are not required assuming leakage current from external components is enough to discharge capacitor. There will only be signal integrity impact to USB performance if the resistors are added. The stub created from placing the optional (not necessary) pull down resistor should be minimized to avoid negative affects. 

    Thanks

    David