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TPS56428: Power Good pin resistor value calculation

Part Number: TPS56428

Hi, How do we calculate the resistor value used to pull up PGood pin to 3.0V? 

  • Hi,

    The smallest size should meet below equation.

    Ron/(Rup+Ron)<Vlow/Vpullup

    Ron is the an open-drain FET Rdson, Rup is pullup resistor, Vlow is the specified logic low voltage , Vpullup is out pull up voltage.

    We can assume max Ron~250ohm, Vlow~0.5v , Vpullup~3v,to get the resistor >12.5Kohm.

    This pull up resistor of 20k~100kohm is recommended to this pull up voltage, in consider of noise and give some buffer here.

    BRs,

    Young