In this circuit I'm using an MCP73832 for battery charging and an AP2210 LDO. The mosfet is a DMP3099L. With the USB disconnected, VBAT set to 4.2V and the MCU (STM32F030F4P6) in standby mode (drawing < 10uA), the total current graph looks like this:
The average current is around 50uA, which seems very high. Candidates for this high average current are the mosfet, the LDO and maybe the MCP73832 (but VCC is not connected, not sure if it can run from VBAT alone, the datasheet doesn't say anything about this that I can see).
This high average current consumption is the main problem, but perhaps the spikes are related?
The frequency of the spikes decreases with VBAT voltage, and their cadence is not fixed. For example, here's the graph when VBAT = 3.8V, where the spikes are between 6 seconds and about 0.8 seconds apart.
The STAT pin is connected to a GPIO on the MCU which is in high impedance mode while the MCU is in standby mode.
So the questions are:
- Why is the average current consumption so high?
- What is causing the intermittent current draw?