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BQ25070 battery current draw

Gerardo Barroeta
Prodigy 40 points
Other Parts Discussed in Thread: BQ25070

Hello everyone,

Playing around with the BQ25070 LiFePO4 charger EV KIT, we noticed that there is some (leakage?) current flowing into the chip from the battery when no input is connected.

This current is approximately 100uA. This is very undesirable because it can drain the battery in a few days. However I noticed that if I remove the jumper that connects the \CHG pin to an LED and pull-up resistor, this current disappears. We also tried removing the jumper shunt and tying \CHG directly to the BAT output, with several resistor values up to 100k and the current does not seem to decrease at all. Only way to get rid of this is leaving \CHG floating.

What is the reason for this? any suggested work arounds that do not involve simply not using this pin and detecting charger insertion through voltage dividers/zeners/comparators?

Thanks

  • 0
    TI__Guru*** 147665 points
    The spec for battery leakage is IBAT(PDWN) in the electrical specs table.
    To achieve the lowest leakage into the BAT pin, you can add an external series FET between the BAT pin and battery. If VIN > Vth+VBATREG you could use VIN to drive the gate of an NFET, drain tied to BAT pin. If VIN is not high enough, you would have to use a PFET, source tied to BAT pin, with pull up resistor and a second NFET at the gate