Internal temperature sensor for the MSP430 - energia
The datasheet, only gives a typical slope of 3.55 mV/C on the sensor.

It doesn't give high or low limits on the slope.

It doesn't give any offset, neither typical or limits.

The equation in the notes implies that the relationship is linear, however.

So a two-point calibration should be sufficient, which means taking a reading at two different temperatures and deriving the actual offset and slope through algebra.

If you trust the slope value of 3.55 mV/C you can do a single point calibration.  If your device is only used over a relatively narrow temperature range this can be OK, because you can calibrate your single point in the working range, then the temperature error will be zero at that temperature and increase as you move away at the rate of \$(TC_{actual} - TC_{typical}) * T\$. 

In my experience the slope value is pretty close to 3.55 mV/C, but unfortunately I don't have data that I can share about that.  Offset varies, especially across different production batches.