28.2.2 Peripherals Using Voltage References

The devices of the AVR SD family have a number of peripherals that can use a voltage reference.

• The DAC peripheral is using the voltage reference controlled by the VREF.DAC0REF register.
• The AC peripheral is using input pins, but the negative input can be routed to use the voltage reference controlled by VREF.ACREF. The instances of the AC peripheral share the same voltage reference from the VREF peripheral. In addition, each AC instance has its own, independent voltage divider for the incoming reference voltage, controlled by the respective ACn.DACREF register.
• The ADC peripherals are providing their own control register for their internal voltage reference, the Reference Selection (REFSEL) bit field in their respective ADCn.CTRLC registers. Note that ADC0 and ADC1 are accessing two different, independent voltage references. This redundancy can be used to improve functional safety:
  • ADC0 is using a voltage reference residing in the VREF peripheral.
  • ADC1 is using a voltage reference internal to the Voltage Regulator Monitor (VMON). VMON is a part of the Sleep Controller (SLPCTRL) peripheral. The VMON must be enabled when operating ADC1.