I've question similar to another SO question, with some minor differences, which I'll explain below:
I'm designing a circuit which should work with 3 AND 4 AA batteries. Idea is to create two models, one with slightly longer life than the other one (33% more). The circuit uses an STM8L, and would periodically "wake up" to perform some periodic stuff, and then go back to sleep, typical of certain battery powered devices. I'm planning to use a voltage regulator of 3.3 V output. I want to know which kind of regulator would make more sense (LDO vs switching). My use case doesn't require any RF application, so bit of output noise is acceptable (meaning switching regulator should be just fine).
With 3 AA battery system, based on the discharge characteristics, "95% + charge" would be available upto 2.8-2.9V. So, a LDO regulator, will be giving on average 3.8V battery regulated output 3.3V, which makes it around 85% efficient. This is putting it on par with most switching regulators out there. Please correct if wrong.
With 4 AA battery system, based on the discharge characteristics, regulator will be on average 4.5V battery regulated output 3.3V, which is <75 % efficient. Now we are getting into that territory where switching regulator would most definitely start to shine.
Please let me know if my above understanding is on the correct path. Should I use a LDO/switching regulator or design the two circuits separately one with LDO other with switching regulator? Any other suggestion also welcome.