30.3.2.2 Input and Reference Selection

The input selection to the ACn is controlled by the Positive and Negative Multiplexers (MUXPOS and MUXNEG) bit fields in the MUX Control (ACn.MUXCTRL) register. For positive input of ACn, an analog pin can be selected, while for negative input, the selection can be made between analog pins and internal DAC reference voltage (DACREF). For details about the possible selections, refer to the MUX Control (ACn.MUXCTRL) register description.

The generated voltage depends on the DACREF register value and the reference voltage selected in the VREF module, and is calculated as:

V_{DACREF} = \frac{DACREF}{256} \times V_{REF}

The internal reference voltages (V_REF), except for V_REFA and V_DD, are generated from an internal band gap reference.

After switching inputs to I/O pins or setting a new voltage reference, the ACn requires time to settle. Refer to the Electrical Characteristics section for more details.