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TPS54325: PG behavior(TPS54325/TPS54525/TPS40170)

Part Number: TPS54325
Other Parts Discussed in Thread: TPS54525, TPS40170

Hi team,

 

I have a question about PG(Power Good) behavior of following devices so could you help this question?

             1. TPS54325

             2. TPS54525

             3. TPS40170

 

Question:

These have EN pin and PG pin.

I'd like to ask behavior of PG pin when device is disabled.

All devices have open drain PG output so I think PG pin state should be Hi-Z.

 

Regards,

  • Hi,

    If you mean when EN is low, then PG pin state should be Hi-Z if it has a open drain output. Thanks.

  • Hi Iven,

    I'm Kai working with Sato-san.

    Customer took captures of each PG behavior and I attached it.

    in customer case, PG is pulled up to external 3.3V output.

    CH1: 3.3V_EN/ this voltage shows external 3.3V DCDC enable input

    CH2: 3.3V_output/ this voltage shows external 3.3V DCDC output

    CH3: 3.3V_PG/ this voltage shows external 3.3V DCDC PG output

    PG pin state of TPS devices that sato-san mentioned in this title should be Hi-Z if it has a open drain output.

    in customer case, PG is tied to external 3.3V so PG output at EN "Low" should be pulled up to 3.3V but actually it is tied to GND in attachment.

    do you know the reason why PG output is not Hi-Z but tied to GND when EN is low?

    PG behavior.pptx

    Regards,

    Kai

  • Hi,

    It seems the behavior's not an open drain output when EN is low of these three device, so the PG output is not Hi-Z. It might because although the device is shutdown by EN, there's still a signal designed to open PG FET to ground it. It's should be a common design but we still need to check it if you use another device. Thanks.

  • Hi Ivan,

    thank you for your comment.

    I understand all three devices the PG "behavior's not an open drain output when EN is low of these three device, so the PG output is not Hi-Z.".

    i think if Vin/Vcc is tied to GND(no power supply), PG should be Hi-Z.

    what do you think about it?

    Regards,

    Kai

  • Hi,

    Yes, if the device is totally no power supply. Thanks.