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UC3906 battery reverse polarity leakage current

John Thomas71964
Prodigy 80 points
Other Parts Discussed in Thread: UC3906

If i reverse the 12V SLA battery polarity, i notice there is about 80mA current flowing from UC3906 ground to pin11 which have a series resistor 140ohm and a diode back to the SLA. Is this normal?

  • 0
    TI__Guru**** 150950 points

    Yes, applying 12V backwards will make the trickle charge circuit conduct, limited only by your resistance.

    Note that applying a reverse voltage violates the voltage rating for many of the pins and the current rating of the trickle bias pin.  You need to design a separate reverse voltage protection circuit for the IC or make sure that the pack cannot be inserted backwards.