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TUSB8041: Adjustment of GRSTz signal delay time

kyoshi.oyaizu
Prodigy 10 points
Part Number: TUSB8041

Hi Team:

I have two questions.

I want to adjust the reset delay time of pin 50 (GRSTz pin)of TUSB8041.

I would like to know the constant of the capacitor that makes the desired delay time, so please tell me the calculation formula.

Also, I would like to check on the timing requirements for power supply rise.

I understood that if VDD33 rises and then VDD rises, the GRSTz signal must be de-asserted for at least 3ms after VDD rises.

Is my understanding correct?

Kind regards,

  • 0
    TI__Prodigy 560 points

    Hello,

    To calculate the approximate time delay of the passive reset circuit you would use the equation t=R*C, where R is the internal pull-up resistance of GRSTz (nominally 22k) and C is the desired capacitor connected from the GRSTz pin to GND.

    For example, consider a 1uF capacitor. We would have: t=(1e-6)*(22e3)=22 ms.

    You are partially correct. The GRSTz signal must be deasserted for at least 3ms after both VDD33 and VDD are stable. But, in addition, VDD must be stable for at least 10us before VDD33. So VDD must rise before VDD33.

    Regards,

    Alex