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TUSB1002: AC Coupling Capacitors for USB 3.1 Gen 2

Sadanori Kato
Guru 36530 points
Part Number: TUSB1002
Other Parts Discussed in Thread: TUSB1044

Hi,

We have some questions for TUSB1002 and TUSB1044 as below, so could you please give us your advice ?

Q1. AC Coupling Capacitors for TUSB1002
TUSB1002 data sheet is revised to support "USB 3.1 ECN Rx AC Coupling Capacitor Option" as below, however the value of RX1 AC coupling capacitor(100nF) is different from one of RX2 AC coupling capacitor(330nF).
Can 330nF be applied to RX1 AC coupling capacitor ?
Moreover, could you please tell us that reason why 100nF can be applied to RX1 AC coupling capacitor ?

https://e2e.ti.com/support/interface/usb/f/1008/t/639091

Q2. AC Coupling Capacitors for TUSB1044
Can TUSB1044 support "USB 3.1 ECN Rx AC Coupling Capacitor Option" ?
Moreover, could you please tell us the recommended value for those capacitors ?

- AC Coupling Capacitors
TX : 75nF ~ 265nF
RX : 297nF ~ 363nF

https://e2e.ti.com/support/interface/usb/f/1008/p/623347/2297357

Best regards,
Kato

  • 0
    TI__Mastermind 36085 points

    Hello kato-san,

        I hope I can clarify all your questions.

    • Q1: RX1 AC coupling capacitors are 100nF because they are connected directly to the TX pair of the USB Host; contrary to the RX2 differential pair, which has 330nF AC coupling capacitors, the higher capacitance is due to this pair will be connected to a TX pair on a connector that has its own AC coupling caps (100nF), so the total capacitance in the pair will be reduced to 76.74nF, just above the minimum allowed by the USB specification (75nF). That is why the value of the AC coupling capacitors on RX2 is 330nF, meanwhile on RX1 is 100nF (and no, this capacitance can't be 330 nF, since the required capacitance is from 75nF to 265nF).

    • Q2: Yes, the TUSB1044 supports the "USB 3.1 ECN Rx AC Coupling Capacitor Option", where the AC coupling capacitance must be from 75nF to 265nF (the recommended value by VESA is 220nF). The only fixed value for AC coupling capacitance is 330nF, for the specific case of a RX pair that it is connected to a Type-C connector (as shown in the "USB 3.1 ECN Rx AC Coupling Capacitor Option").

    Best regards,

    Diego.

  • 0 in reply to Diego Cortes
    Guru 36530 points

    Hi Diego-san,

    Thank you for your prompt reply.

    I understood and will contact you if I get additional questions from our customer.

    Best regards,
    Kato