Temperature SensorMPC5644A Microcontroller Reference Manual, Rev. 6Freescale Semiconductor 1229Chapter 27Temperature Sensor27.1 OverviewMPC5644A MCUs include an onboard temperature sensor that monitors device temperature and producesa voltage directly proportional to the internal junction temperature. Internal junction temperature must becalculated by software based on the sampled temperature sensor voltage, sampled bandgap voltage andcalibration parameter values stored in internal flash memory.27.2 Detailed descriptionThe temperature sensor generates a voltage that increases linearly with temperature. Since the voltage isan amplified version of a VBE voltage it is proportional to absolute temperature. This voltage,VTSENS(T), is read by software using the onboard eQADC module and used with the bandgap voltage andconstants stored in flash memory during factory test to calculate device junction temperature.Five calibration parameters are stored in flash memory during factory test:• TLOW is the low temperature factory calibration temperature value.• THIGH is the hot factory calibration temperature value.• VBG_CODE (T LOW) is the bandgap voltage at low calibration temperature (TLOW) sampled by theeQADC and converted to a 14-bit value.• TTSENS_CODE (TLOW) is the temperature sensor voltage at low calibration temperature (T LOW)sampled by the eQADC and converted to a 14-bit value.• TTSENS_CODE (THIGH ) is the temperature sensor voltage at high calibration temperature (THIGH )sampled by the eQADC and converted to a 14-bit value.The calibration points are illustrated in Figure 27-1.
