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LM5022: only powers up between 7.5v to 8.5v UVL?

timcam
Prodigy 10 points
Part Number: LM5022

Hello,

I am using the LM5022 in SEPIC mode. If I power the chip between 7.5v and 8,5v the chip is enabled and works fine.

However, as soon as I go above ~8.5v, the chip goes into shut down almost as if it's in UVL.

I don't understand how this can be? I have a R12 10k and  R13 2.1k divider for the UVL pin. I even tried just pulling the UVL pin to 9v and it still is in shut down.

I tried different ramp-up times, with load and it just stays in shut down unless the Vin is between 7.5v - 8.5v.

Thanks,

Tim

  • 0
    TI__Guru* 78060 points
    Hi Tim,

    The circuit that you should is just regular boost, not a SEPIC. When your input voltage is greater than the output setting point of the boost converter, the circuit will stop switching, no matter what is your ramp up time.

    If you want to use it in a SEPIC, you should build a SEPIC. Please Google online if you don't know the difference between a SEPIC and a boost.

    Thanks,
    Youhao Xi, Applications Engineering.