Hi,
The 16F630 divides down the Vdd for it's reference and the usable input range is about 0.3 to 3.5V with a 5V Vdd. the resoultion is about 0.15V (Vdd/32).
Depending on your application, it may be worth considering the 16F676 with it's 10 bit ADC. The ADC allows you more freedom to add filtering etc in software.

Robert G8RPI.