31.3.2.3 DAC as Source For Internal Peripherals
The analog output of the DAC is internally connected to both the AC and
                                    the ADC and is available to these peripherals when the DAC is
                                    enabled (ENABLE = ‘1’ in DACn.CTRLA). When the
                                    DAC analog output is only being used internally, it is not
                                    necessary to enable the pin output driver (i.e., OUTEN =
                                                ‘0’ in DACn.CTRLA is
                                    acceptable).
