I am a newby to the world of electronics and IC chips, and am looking to make an ATMEGA328 based board to monitor 12v batteries. The board will be powered from the batteries being monitored, with a regulated power supply taking 12v input and outputting 5v to the board. The data sheet for the ATMEGA328 chip says that AVcc should be connected externally to Vcc via a low-pass filter. A bit of internetting tells me the low-pass filter will filter out noise above a specific frequency, and provides links to calculators that show the affect of different resistor / capacitor pairs.
My problem is that, I have no idea what frequencies I need to filter! All / any advice much appreciated.
Further info: voltage measurements will be via voltage divider circuits, amp hour consumption will be via sensors, all of which will be connected to analog pins for ADC conversion.