NXP Semiconductors MPC5644A, Reference Manual, Page: 1229 / 1735

Temperature Sensor
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 1229
Chapter 27
Temperature Sensor
27.1 Overview
MPC5644A MCUs include an onboard temperature sensor that monitors device temperature and produces
a voltage directly proportional to the internal junction temperature. Internal junction temperature must be
calculated by software based on the sampled temperature sensor voltage, sampled bandgap voltage and
calibration parameter values stored in internal flash memory.
27.2 Detailed description
The temperature sensor generates a voltage that increases linearly with temperature. Since the voltage is
an amplified version of a

V
BE
voltage it is proportional to absolute temperature. This voltage,
V
TSENS
(T), is read by software using the onboard eQADC module and used with the bandgap voltage and
constants stored in flash memory during factory test to calculate device junction temperature.
Five calibration parameters are stored in flash memory during factory test:
• T
LOW
is the low temperature factory calibration temperature value.
• T
HIGH
is the hot factory calibration temperature value.
• V
BG_CODE
(T
LOW
) is the bandgap voltage at low calibration temperature (T
LOW
) sampled by the
eQADC and converted to a 14-bit value.
• T
TSENS_CODE
(T
LOW
) is the temperature sensor voltage at low calibration temperature (T
LOW
)
sampled by the eQADC and converted to a 14-bit value.
• T
TSENS_CODE
(T
HIGH
) is the temperature sensor voltage at high calibration temperature (T
HIGH
)
sampled by the eQADC and converted to a 14-bit value.
The calibration points are illustrated in Figure 27-1 .