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LM5170-Q1: Boost mode operation

kura
Genius 4840 points
Part Number: LM5170-Q1

Whey our customer connect ISETA to AGND at boost mode,there is output of Low side gate pulse.

Please see attahced file.(LO1 has no output,LO2 has output)ISETA Connected to GND.pptx

1.Please tell us the reason why this has output of Low side in this case.

2.Please let us know how much variation of  min gate pulse.

3.If you have solution to make gate pulse to 0 ,please let us know how to do.

Regards,

  • 0
    TI__Guru* 78070 points

    Hi Kura,

    Thank you for posting.  This is caused by the small offset voltage, which may make ISETA=0V appears to be a few mV for the gm input. At no load you may consider to pull EN1/2 to GND to stop switching, or you may consider to add a dummy load at the boost output rail to prevent the loss of voltage regulation.  If neither is acceptable, you should add a simple charge pump (see the attachment) to create a small negative bias voltage, and use it to pull ISETA to slightly negative, then it will  overcome the offset voltage and achieve no load regulation.

    ISETA-Pulldown.vsd

    Thanks,

    Youhao Xi, Applications Engineering