BQ24061: Prevent damage by reversing battery polarity

Edison Achelengwa

Other Parts Discussed in Thread: BQ24061

I have a charger which uses the Li-ion linear charger, BQ24061. I am precisely using the application circuit on page 12 of the datasheet (Figure 16: Application Circuits, the second one which corresponds to BQ24061). I am charging the 18650 3.7V-nominal 2600-mAhr Li-ion cell. Unfortunately I designed my board such that I can flip the polarity of the 18650. I noticed that when I do that, the charger ic becomes damaged and I cannot use it anymore.

I believe the source of my problem is the high current which the BQ24061 has to carry when I flip the polarity of my battery. How can I avoid this problem. Right now I am thinking of using a pass PFET and comparator. I would like to hear some suggestions.

Thanks

Edison

over 12 years ago

0 Loren Siebert 1 over 12 years ago

TI__Genius 13935 points

You might consider putting a shottkey diode between the out pin (10) and the BAT pin voltage sensing resistor R8. This way the battery voltage would still be measured corrrectly, but the out pin would be protected from reverse polarity. The Bat pin would still be forced to a negative voltage, but the 200 Ohm resistor may be enough to protect it. If the 200 Ohms is not enough it may be possible to select a larger resistor. The BAT pin goes to a buffer and should be high impedance, but too large of a resistor would likely cause stability issues.

0 Jeff F over 12 years ago in reply to Loren Siebert 1

TI__Guru*** 149395 points

Try http://www.ti.com/lit/an/slva139/slva139.pdf

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BQ24061: Prevent damage by reversing battery polarity