I started a thread entitled "capacitor recommendation request" that I no longer think captures the essence of what I'm trying to find out... so I'm re-posting a simplified version of my question here. The question is....
If you would like to hold a steady, regulated 5V to power an AVR, sensor, and keep the AREF pin at a known, fixed value using a 4.8V battery (which ranges from about 6V fully charged down to 4.5V over time)... while simultaneously using that same battery to drive a couple servos which can draw a few amps of current in short bursts when making quick moves... what would the best approach be?
My current setup involves the 4.8V battery supply wired straight to the servos, and then also into a 100 uF cap which is the input to a 5v low dropout linear regulator, with another 100 uF output cap that drives the AVR, sensor, and AREF pin. The problem I've been seeing is that the momentary bursts of power required by the servos cause the voltage at the AREF pin to drop for an instant causing my ADC conversions to be inaccurate.... even though I have two caps (.1uF & 22pF) at the AREF pin. It was suggested to me (by Bob) that I use a Shottky diode to decouple the servos from the capacitor to the 5V regulator... which I tried, but did not have success with until increasing my battery supply voltage to a higher voltage. I noticed, however, that the problem is also fixed by just using the higher supply voltage alone... without the Shottky diode.
If I'd like this to work with a 4.8V battery, however, I'm assuming I would need to use one of those switched mode regulators that can output a higher voltage than its input. So what I'm wondering is whether I should get one that takes an input from some range such as 4V to 8V and outputs a regulated 5V... or would it be better to use two voltage regulators... a switched mode to bring the level up to about 6V and then a linear mode one to hold the 5V from the input 6V? I'm not familiar enough with how (or how well) the switched mode regulators work and am just wondering if by using only the one and expecting it to bring my 4.8V up to 5V will end up with the same problem I was previously seeing with my initial setup... i.e. voltage dropping any time the servos make a quick move.
Anyway, I hope this was clearly enough worded that it's understandable what I'm trying to do... and would greatly appreciate any feedback. Bob & Kartman, thanks for your replies to my previous post.