Can I (attempt to) measure a voltage that is higher that the ADCs Vref, without damaging my IC?

I'm trying to measure the battery voltage using a resistive divider, and using the internal 1.1V bandgap voltage. I selected the resistors so the voltage would be around 1V when fully charged.

My project can however also be power by a wall-adapter, which exceeds the batteries voltage, resulting in a voltage higher than 1.1V at the ADC.

In the datasheet the table of ADC Characteristics seems to indicate that the maximum input voltage is Vref. Though I'm not sure if that's the maximum voltage is can convert, or if that's the maximum voltage that's allowed.

Elsewhere in the datasheet it says: Single ended channels that exceed VREF will result in codes close to 0x3FF, which seems to indicate it isn't a problem to exceed Vref (as long as it's below Vcc).

The part I'm using is an ATtiny13A, but the relevant sections of the datasheet seem identical to the ATMega328.

1 Answer 1


Yes, you can go above VRef.

Voltage on any Pin except RESET

with respect to Ground ................................-0.5V to VCC+0.5

And as the ADC reference says anything above VREF will give you the maximum value (it will saturate).

So powered from 5V you can apply anything from -0.5V to +5.5V safely. That's basically the supply voltage plus one diode drop for the ESD protection diodes within the pin.

The ADC is just comparing two voltages. The VREF isn't used to power anything.


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