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TPS544B20: dot connection of PGOOD pins

Shunsuke Yamamoto
Expert 6551 points
Part Number: TPS544B20
Other Parts Discussed in Thread: TPS544C20

Tool/software:

Hi team,

Is it possible to connect sveral PGOOD outputs from several TPS544B20 and TPS544C20 like the figure below? The reason why my customer does it is to reduce the number of pins on microcontroller to monitor PGOOD outputs. My customer expects all ICs gets off when ither one PGOOD pin or other PGOOD pins gets low output. 

Best regards,

Shunsuke Yamamoto

  • +1
    TI__Guru 54270 points

     

    Yes.  The Power Good pins are Open-Drain outputs.  When connected like this, the combined power good signal will go low if any of the device's pull Power Good low.  Generally, when connected like this, they all share a single pull-up resistor rather than all having their PGOOD pulled up locally by their converter's BP 3 or BP6 regulator.

    The pull-up current should be low enough that it can be pulled low by any one of the devices, since all are TPS544B20 or TPS544C20, that should be 5mA or less total pull-up current.

    Note:  Adding a small (10-Ω or less) series resistor between each device's PGOOD pin and the common PGOOD signal back to the micro-processor can be a useful tool for de-bug and identifying which device is asserting PGOOD during failure analysis.