Hello, I have a simple circuit with an STNS01 charging a 150mAh single cell battery and am using the LDO to power an STM32F042 and a couple of other small devices. It mostly seems to work OK, however if I pull the SD line high using the micro (or an external short to the 3.1V LDO output), the output of the LDO drops to 1.28V, rather than zero. Some devices on the LDO output can still operate at this voltage so the drain on the battery doesn't drop to the <500nA mentioned in the datasheet, instead I'm seeing a battery draw of ~550uA. I'm not sure why the LDO isn't being fully disabled.
If I unplug the battery and reconnect it the current draw drops down to about 10nA so I'm sure the STNS01 is capable of fully disabling the LDO, but for some reason it isn't.
In a test I set all the signals in the attached schematic (nCHARGE, CHARGE_EN, SHUTDOWN, BATT_SENSE and nSENSE_EN) to High-Z and then used a jumper on J3 to short SHUTDOWN to 3V3 (actually 3V1, just mis-labled). This had the exact same result, of 550uA draw.
Any ideas for debugging or advice would be greatly appreciated.
Cheers,
Mike
