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TPS54JA20: PGOOD pin connection

Reagan Li
Prodigy 545 points

Part Number: TPS54JA20

Hi team,

The PGOOD pin should always connect to VCC or it could connect to an external voltage rail ?

Customer found that if the PGOOD pin of some device (not TPS54JA20 ) pull up to external P3V3, the PGOOD will be high even when the device is power off. So customer had to pull up the PGOOD to the VREG which generated by the device to avoid the PGOOD be high before the device output normally.

I am wondering if the PGOOD pin of TPS54JA20 should connect to VCC too .

Thanks! 

  • +1
    TI__Mastermind 27615 points

    The PGOOD can be connected to an VCC or an external source. The datasheet scopes plots have the PGOOD connected to VCC. 

    If the external source is active and the input voltage to the TPS54JA20 is off.  The PGOOD pin can not assert low. 

    The PGOOD pull down mosfet needs voltage on the gate to assert and pull the PGOOD down.   If the vin pin voltage is greater than 1.5V then the PGOOD pin will pull low but with reduce current sinking capabilty.  If the VIN pin voltage is 0V on TPS54JA20, there is no voltage to apply to gate of PGOOD mosfet to assert pin.. 

  • 0 in reply to David_Daniels
    TI__Prodigy 545 points

    Hi David,

    Noted, I understand the PGOOD function now. Thanks for your comment!

    Regards

    Reagan