30.3.2.1 Input and Reference Selection

The input selection to the AC is controlled by the Positive and Negative Input MUX Selection (MUXPOS and MUXNEG) bit fields in the Multiplexer Control (ACn.MUXCTRL) register. For positive AC input, an analog pin or internal connections can be selected. For negative input, the selection can be made between analog pins and the internal reference voltage.

When the negative input is an internal reference voltage, the generated voltage depends on the Scaled Reference Voltage (ACn.REFSCALE) register value and the reference voltage selected in the VREF peripheral and is calculated as:

V_{REFSCALE} = \frac{REFSCALE}{2^{SIZE_REFSCALE}} \times V_{REF}

where SIZE_REFSCALE = 8.

Refer to the VREF - Voltage Reference section for details on available reference voltages.

The AC needs time to stabilize after changing inputs to the I/O pins or setting a new voltage reference. Refer to the Electrical Characteristics section for more details.