I'm building a board (simple toy) that needs two power voltages. The first part has MCU and sensors and can use anything from 3.3 to 2.6 volts. The second part has an audio amplifier and servo motors; it needs 5 to 5.5 volts. The total current is ~50mA on average, with short spikes to 80mA when the speaker is active.
I currently use 4 AA cells and two linear regulators (5V and 3V3), but this has unwanted drawbacks:
- lowering 6V to 3V3 wastes almost 50% of energy;
- it only works with fresh batteries. As soon as the power pack voltage drops below 5V, the first regulator stops working, and the 5V part becomes underpowered.
My next best idea is to use 3 AA cells, a boost DC-DC regulator to power the 5V part, and a linear regulator to get 2V8. This way, I can use batteries until dry; they should go about 1V each in the end.
Is it a good design, or is there a better one? This is one of my first boards, and I don't have a good intuition, even less knowledge.