I'm trying to charge an Adafruit 500mAh battery with a custom PCB I made. However, when I include the AP9101C protection IC (with accompanying DMG6968 common-drain MOSFET pair), it fails to charge. This is the circuit as it's meant to operate:


USB_HALF stays at 2.5V, indicating No Battery Present. The battery discharges fine in this configuration (as tested with a few LEDs, 30mA draw), which implies that the MOSFETs are ON.

I can get the battery to charge correctly (and USB_HALF subsequently is pulled low) in this configuration without those 2 ICs:


Note that the wire running off to the left leads to the load on this PCB, which isn't soldered on these test boards. So save for the temporarily connected LED load, the parts shown in the schematic are the only parts present.

Any ideas?


1 Answer 1


Solved. As seems to be the norm with me, it was a solder bridge on the SOT-23-6 MOSFETs. They didn't appear shorted upon visual inspection, but I guess it goes to show that you should never assume anything, no matter how many SOT-23-6 you've soldered before!

Thanks to anyone who took a look, and sorry if anyone took any time trying to find a solution to my silly problem.


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