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TUSB4041I: Power on Sequency

Vincent Li00
Intellectual 2035 points
Part Number: TUSB4041I


Hi guys

our customer is using our TUSB404I . By following our EVM, we found there is a question: Please see below that is the power explanantion.

As above description, I think the VDD33 is powered on before VDD11, right? Also, i checked the schematic. There is only a 1uF cap between GRSTz Pin and GND.

However, our TUSB4041I datasheet show as below:

So in fact, how do we control the power on sequence?

Thanks

-Pengfei

  • 0
    TI__Guru**** 151810 points
    VDD33 should be stable before VDD11.
  • 0 in reply to Brian Zhou
    TI__Guru 60870 points
    The important requirement is that both power rails are stable for approximately 3ms before GRSTz goes high. If there is an actively driven GRSTz signal, then power sequencing does not matter. If GRSTz is being generated by a passive circuit consisting of an external capacitor and an internal pullup resistor, the issue with VDD33 ramping before VDD is that the internal pullup resistor is tied to the VDD33 rail and the GRSTz line may be pulled high before VDD finishes ramping. On the EVM design, VDD33 and VDD ramp almost simultaneously, so this is not a concern.

    Regards,
    JMMN