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TUSB4020BI: Are there any power sequencing restrictions ?

Hironori Kishida
Prodigy 20 points
Part Number: TUSB4020BI

Are the following statements in the data sheet inconsistent?
・ 8.3.4 “The TUSB4020BI does not have specific power sequencing requirements with respect to the VDD or VDD33”
power rails. ”
・ 7.7 (2) “Then VDD must be stable minimum of 10 μs before the VDD33.”

  • 0
    TI__Guru 60870 points

    Hello Kishida-san,

    The entire note for 7.7 reads:  (2) There is no power-on relationship between VDD33 and VDD unless GRSTz is only connected to a capacitor to GND. Then VDD must be stable minimum of 10 μs before the VDD33

    The text in orange is meant to explain that the device does not require a particular power sequence, however, using a passive reset circuit that relies on the internal pullup on the GRSTz creates a power sequencing concern since we do not want the pullup resistor to 3.3V to be enabled well before the 1.1V ramps preventing a proper reset.  We have found that as long as 3.3V and 1.1V ramp closely together the passive reset works well.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 20 points

    Dear JMMN

    Thank you for your answer. I understand.

    Regards

    H.Kishida