What is the internal voltage of an iPod 4/5G?

Hey, I am looking at modding either a 5G or 4G ipod with the compactflash internal ssd and then adding a FM transmitter. My problem is though that I can not find the internal voltage that the ipod runs on anywhere on the internet. I need this because as I have the larger version of both these ipods I wish to add an internal fm transmitter (belkin tunecast 1 or equivalent) for use in the car. I know that most electronic devices run at 5v and was wondering if the ipod has a dc-dc transformer in it to transfer the voltage from the 3.7v lithium cell. Am I right to assume that the dc-dc converter only turn on when the ipod is on? If so I will just use a voltage divider to supply my 3v input for the FM transmitter. Any help would be greatly appreciated. Robert Springer