I need to find a voltage regulator or buck/boost converter to supply 5V. issue is, this will be used on a standalone arduino/MSP328P that will run off of some AA batteries. I'm wanting the extend the life of the project so the batteries will last as long as possible. I plan to put the MSP328p into sleep mode for most of the time and only wake up it with an interrupt from a vibration sensor. So, most of the time this will be in sleep mode and i don't want to waste battery power. I'm thinking i need a low-quiescent voltage regulator or buck/boost converter that has less than 200uA when the msp328 is in sleep mode. what is the best option for a voltage regulator in this situation? Also, i don't plan on using more than about 300mA of current when the device is fully turned on and working.
What requires 5V?
A standalone ATmega328P will run on any voltage between 1.8 and 5V. The lower, the less power required and the longer the battery life. For years on 2 AA batteries, if you do it right.
jremington is right you might not need a boost converter.
But please check the datasheet Electrical Characteristics section for the conditions. Supply voltage and clock frequency are link together. At lower voltages you can no longer run silicon at the same speed as at the maximum voltage.
You can use Brown-Out detection to stop the microcontroller from misbehaving when the voltage drops below the safe operating voltage. But this will cost you a little bit of extra battery. The ATmega has a BOD disable feature that will disable Brown-out detection during sleep. So, you get the best of both worlds.
There might be other limitations when you run at the lowest voltage. This depends on the device and the peripherals it has. You need to check the datasheet of the device in question.