I need to power some pressure sensors that require a stable 5v excitation voltage. The sensor outputs an analog voltage that's proportional to pressure being exerted on the sensor. Currently I'm using the the ADC of the ATmega328 to sample the sensor output. Eventually I'll probably use a separate ADC chip because I want better than 10-bit resolution. Each sensor draws about 5ma, and I could have up to 5 sensors on one board. So if I could find an ADC chip that provided a 5v reference capable of supplying enough current and could read a voltage from 0 to 5v, then that would solve my problem.