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TPS54521 PWRGD Output

Rob Mitrunen
Expert 1685 points
Other Parts Discussed in Thread: TPS54521

Can I depend on the PWRGD output to sink at least 400 uA current for the following operating conditions: input voltage VIN is less than 1.00V.

I ask, because on page 15 of the data sheet (SLV981C - JUNE 2010 - Revised August 2013) it states:

“The PWRGD is in a defined state once the VIN input voltage is greater than 1V but with reduced current sinking capability.”

which implies that PWRGD is undefined when VIN is 1V or less.

 

We have tested on our lab bench with operating condition VIN = 0V, and the PWRGD output is sinking current through pull down resistors - at least for a sample set of one TPS54521 IC. However, given the data sheet statement about VIN conditions where PWRGD is defined, I would like to get feedback from TI whether or not we can count on this in mass production, across all TPS54521 devices.

  • 0
    TI__Guru**** 191445 points
    PWRGD is an open drain output. We specify the leakage current when the PWRGD transistor is "off" and the sink current when the transistor is turned on. I doubt that we would have any other data for it.

    What pull down resistors are you referencing?

    As Vin rises above about 0.6V, some junctions internal to the IC may be forward biased while the internal circuits do not have enough voltage to actively control the functional blocks. You may see that the internal PWRGD FET is not actively turned on at this time allowing the PWRGD signal to be pulled up externally indicating a PWRGD true state. as the input rises above 1V, the internal circuitry takes active control and will pull PWRGD low until the circuit is within regulation tolerances.