neil12:
I put in a request to enable the ADC15/temperature sensor. However - it is the temperature on the die - which does warm up.
To make it be close to the ambient temperature is going to require implementing a power down mode - no power no die warmup - and then on wakeup reading the temperature straight away.
That seems like a very longwinded way to get a rather inaccurate measurement of the ambient temperature. If you want to measure air temperature, use a temperature sensor that is in the air, not embedded inside a heat-generating device and thermally insulated from the air.
On the other hand, if you need to monitor the on-chip temperature for some reason (like, to raise an alarm if it gets too hot) then that would be a good use of this sensor.