I'm working on designing a project that will have a zigbee radio, an attiny84, and a few sensors. This will need to run off batteries (a few AA). My question is on the power supply circuitry. Do I run everything off of 3.3v (the tiny84 will run at a lower frequency on 3.3v), or have separate 5v and 3.3v circuitry (no logic level conversion will be needed). I've been toying with the idea of going the 3.3v and 5v route, however I'm not sure of an elegant way to do it. If I go the route of several diodes to get the voltage drop from 5v to 3.3v I'd be running everything through the one dc converter. Also, it wouldn't be exactly 3.3v. If I use a second dc converter, it would about double the components needed just for power regulation and control. Any help is much appreciated. Thanks much.