I need to power a chip with 1.8V-3.6V operating voltage from 3xAA batteries. And I need a solution to be the most power efficient as it can be. I know I can use for example an LDO regulator for this, but that will be very inefficient considering it must regulate down to around 2.6V to take a full advantage of available battery capacity. And what's more important - the closer the voltage is to 3.6V, the better.
One thing that came into my mind is to power it directly from MCU, which has a much greater voltage range. I/O pins have enough source current for this purpose. So I could use two pins for that. One with series diodes to drop the voltage if it is above 3.6V and the other in parallel without any diodes. Battery voltage could then be monitored and chip could be powered either from one pin or another depending on voltage. Will this work and what are other options I have here? DC-DC converter will add unnecessary complexity and noise to the circuit.
One thing that came into my mind is to power it directly from MCU, which has a much greater voltage range. I/O pins have enough source current for this purpose. So I could use two pins for that. One with series diodes to drop the voltage if it is above 3.6V and the other in parallel without any diodes. Battery voltage could then be monitored and chip could be powered either from one pin or another depending on voltage. Will this work and what are other options I have here? DC-DC converter will add unnecessary complexity and noise to the circuit.