13.11.6.2.2 Enabling, Disabling, and Resetting
The voltage reference output is enabled/disabled by setting/clearing the Voltage Reference Output Enable bit in the Voltage Reference register (VREF.VREFOE).
The temperature sensor is enabled/disabled by setting/clearing the Temperature Sensor Enable bit in the Voltage Reference register (VREF.TSEN).
Note: When VREF.ONDEMAND=0, it is
not recommended to enable both voltage reference output and temperature sensor at the same
time - only the voltage reference output will be present at both ADC inputs.