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TPS775: High Inrush Current right when input crosses dropout threshold

Michael Fumicello
Prodigy 50 points
Part Number: TPS775


I'm trying to track down the reason I'm seeing a 1A inrush for ~10uS during the turn on of the TPS77533.  The inrush occurs the moment the 5V input crosses the dropout voltage of the regulator, while the output is still zero.  As the 3.3V output rises, I also see the normal inrush that I would expect to see for 10uF output cap, which is a little under 200mA and close to my calculated inrush.  See attached image of the LDO turning on.

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  • 0
    TI__Guru 55940 points
    Hi Michael,

    So that I can better help debug, could you give a little more information about what is occurring around the LDO startup? For example, what is the status of /EN during startup? Is it tied to GND or does it switch at a given time? Is there anything else switching in your system during the LDO startup? If so, does this overshoot occur when you isolate the LDO?

    Very Respectfully,
    Ryan