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TUSB1044: Changing from recommended value of AC coupling capacitor

Takashi Onawa
Genius 13200 points
Part Number: TUSB1044


Hi Team,

One of my customer would like to use 440nF as AC cap on TX line for their BOM reduction. In general high-speed transmission, I think that there is no problem for using larger capacitance values. But there is a restriction on that value in USB3.1 ECNs.

Can't we use larger capacitance value cap for AC coupling in USB3.1 application and why?

Please let me know if that value is used something in Link up sequence, or if the changing may introduce something issue.

Regards,

Takashi Onawa

  • 0
    TI__Mastermind 36085 points

    Hello Onawa-san,

        Per specification, the AC coupling capacitance must be between 75 and 265nF, there is only one ECN allowing optional capacitance (330nF) for the RX differential pairs. The customer must keep the design within this margin if they want to be compliant.

    Regards,

    Diego.