New Application Note - Measuring the Power Supply Voltage

[dkinzer]

One of our customers is building a battery-powered application and needs to monitor the battery voltage. This cannot be done using the GetADC() function as one might at first think. The new application note shows how to use one of the special features of the ATmega's A/D converter - the internal voltage reference. The concepts illustrated in this application note can be modified to exploit other special features of the A/D converter such as performing differential conversions.

AN217 - Measuring the Power Supply Voltage

[Don_Kirby]

If I use the internal voltage reference, can I eliminate the AVCC and AREF connections at the chip (ZX44)? I have to scale my inputs with a divider anyway, so I could save 2 caps and an inductor if those connections aren't needed.

-DK

[dkinzer]

I think you'll want to keep them. Atmel suggests using an external decoupling capacitor on Aref to reduce the effects of noise on A/D conversions. The AVcc connection is required, with or without the L/C filter, because that's what powers the Port A circuitry. It also powers the analog-to-digital converter and Atmel recommends using the L/C filter on AVcc if you use the A/D converter regardless of which reference you're using.