PXR40RM Datasheet, PDF (1430/1434 Pages) Freescale Semiconductor, Inc – PXR40 Microcontroller

34.3 Temperature formula
The temperature formula is shown in Figure 34-2.
Temperature Sensor
T = T_LOW +
T_{TSENS_CODE}(T) x  – T_{TSENS_CODE}(T_LOW)
T_{TSENS_CODE}(T_HIGH) – T_{TSENS_CODE}(T_LOW)
x
(T_HIGH
–
T_LOW)
where:
Notes:
T_{TSENS_CODE}(T_LOW)
=
V_TSENS(T_LOW)x
V_ref0
2¹⁴
T_{TSENS_CODE}(T_HIGH)
= ^{VTSENS(THIGH)x}
V_ref0
2¹⁴
V_{BG_CODE}(T_LOW)
=
V_BG(T_LOW)
V_ref0
x 2¹⁴
V_{BG_CODE}(T) =
V_BG(T)
V_ref
x 2¹⁴
T_{TSENS_CODE}(T) =
V_TSENS(T)
V_ref
x 2¹⁴
 = ^{VBG_CODE(TLOW)}
V_{BG_CODE}(T)
(Stored in device flash during factory calibration)
(Stored in device flash during factory calibration)
(Stored in device flash during factory calibration)
• V_TSENS(T) is the temperature sensor output sampled by the ADC
• V_BG(T) is the bandgap voltage sampled by the ADC
• V_ref is the ADC reference voltage
• V_ref0 is the ADC reference voltage during factory calibration
• T_LOW is the low temperature factory calibration temperature (stored in device flash)
• T_HIGH is the hot factory calibration temperature (stored in device flash)
Figure 34-2. Temperature formula
The following sections detail the values required and where to get them.
34.3.1 T_LOW and T_HIGH
T_LOW is the factory low calibration temperature; T_HIGH is the hot factory calibration temperature. These
values are stored in shadow flash memory during factory calibration. See Section 34.3.6.1, Temperature
Calculation Constants Register 0, for details.
34.3.2 T_{TSENS_CODE}(T_LOW) and T_{TSENS_CODE}(T_HIGH)
T_{TSENS_CODE}(T_LOW) is the sampled output voltage of the temperature sensor during low temperature
factory calibration. T_{TSENS_CODE}(T_HIGH) is the sampled output voltage of the temperature sensor during
hot temperature factory calibration. These values are stored in shadow flash memory during factory
calibration. See Section 34.3.6.1, Temperature Calculation Constants Register 0, for details.
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
34-3