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TPS70933 power on inrush current when IC enable

Paul Yeh
Genius 14945 points

Hi Expert,

My customer find there is big inrush current when TPS70933 is enable. And the peak current is around 800mA.

But there is no spec. in our datasheet, so customer concerns this peak current may damage the IC.

I also attach test waveform and schematic for your information. Ch1 is output voltage and Ch2 is input current.

BTW, the input voltage is 19.5V from AC adaptor.

Pls. advise your comments then I can feedback to customer.

Thanks

       

  • 0
    TI__Guru 55940 points
    Hi Paul,

    There is a delay before current limit will kick in which will allow larger inrush current initially. This is normal and permits for a faster startup. The amount of inrush current will vary by the amount of capacitance on the output of the LDO.

    In your plot, it is actually possible to see where the current limit kicked in (when the value dropped to 280mA).

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Genius 14945 points

    Hi Ryan,

    Thanks for your comment. But I still have one question need your double confirmation.

    How to judge this inrush current level and spec. for TPS70933?

    How can I tell customer this inrush current they measured should be ok in present design?

    Thanks

  • 0 in reply to Paul Yeh
    TI__Guru 55940 points
    Hi Paul,

    We do not have a specification for initial inrush current. Initial inrush current is normal; however, it is not limited by the LDO.

    Very Respectfully,
    Ryan