I have a small hobby project which includes MCU and some peripherals.
It is powered by 3.3V power source and consumes 200mA-800mA for up to a minute. However, most of the time it's in deep sleep mode where is consumes very little current (as low as 5 µA, hopefully) in order for it to last longer when powered by battery.
Now I would like to power my project by USB when USB is connected, or by one cell LIPO battery when USB is disconnected. When USB is connected I would like it to both power the circuit and charge the LIPO.
Here is the high level scheme I had in mind:
Since USB voltage (5V) is always higher than LIPO voltage,
D2 make sure that when USB is connected the LIPO is disconnected from the DC converter, and when USB is disconnected the LIPO charger is disconnected.
My questions are:
- Does my high level scheme make sense? Any special consideration for selecting
- My main concern is how to select the DC converter.
Input voltage ranges from 3V to 5V although I can probably live with the converter shutting down when its input is below 3.3V as most of the LIPO power is consumed before it gets lower.
I'm looking for a high efficiency converter that can handle efficiently both high currents and very low currents, in order to make the battery last longer.
Would a step down converter be a better choice than LDO? What parameters should I look for in the data sheet?