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TPS65218: PWR_EN best practice

Aaron Spaete
Expert 4527 points
Part Number: TPS65218

Team,

My customer has the following question regarding the TPS65218 powering up a AM335x processor. 

I am troubleshooting another engineer's design

he has PWR_EN (pin 46) pulled up via a 100K resistor to the 3.3 volts generated by DCD4 (pin 15). the voltage input is 5V

I believe this is causing the PMIC device to occasionally not come out of reset (PGOOD is always low). I don't think this is good  practice.

Ideally, I believe PWR_EN should be asserted high tbd msec after the input 5V has stabilized
and deasserted low tbd msec before or during when the main 5V goes out of regulation
during a shutdown

is this correct?

Regards,

Aaron

  • 0
    TI__Genius 16410 points

    Hi Aaron,

    If PWR_EN is only connected to an output, I guess they are using another ON method to turn on the PMIC.  There are a few options listed in the Power-up Sequencing section of the datasheet.  If any of these happen, then the device will turn on, and wait for PWR_EN to be set high.   It sounds like this will always be set high if it's connected to DCDC4, so no issue there.

    So the PMIC should be enabled each time as long as one of the other events happens, like push-button being pressed on PB pin.

    If this doesn't always happen, they can instead use the method you suggest, where PWR_EN is being asserted to enable the PMIC, and then de-asserted to disable the PMIC.

    Regards,
    Karl