C8051F960-B-GM Datasheet, PDF (97/492 Pages) Silicon Laboratories – Ultra Low Power 128K, LCD MCU Family

C8051F96x
5.8. Temperature Sensor
An on-chip temperature sensor is included on the C8051F96x which can be directly accessed via the ADC
multiplexer in single-ended configuration. To use the ADC to measure the temperature sensor, the ADC
mux channel should select the temperature sensor. The temperature sensor transfer function is shown in
Figure 5.8. The output voltage (V_TEMP) is the positive ADC input when the ADC multiplexer is set correctly.
The TEMPE bit in register REF0CN enables/disables the temperature sensor, as described in SFR
Definition 5.15. REF0CN: Voltage Reference Control. While disabled, the temperature sensor defaults to a
high impedance state and any ADC measurements performed on the sensor will result in meaningless
data. Refer to Table 4.12 for the slope and offset parameters of the temperature sensor.
V_TEMP = Slope x (Temp_C - 25) +Offset
Temp_C = 25 + (V_TEMP - Offset) / Slope
Slope ( V / deg C)
Offset ( V at 25 Celsius)
Temperature
Figure 5.8. Temperature Sensor Transfer Function
5.8.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature mea-
surements (see Table 4.13 for linearity specifications). For absolute temperature measurements, offset
and/or gain calibration is recommended. Typically a 1-point (offset) calibration includes the following steps:
1. Control/measure the ambient temperature (this temperature must be known).
2. Power the device, and delay for a few seconds to allow for self-heating.
3. Perform an ADC conversion with the temperature sensor selected as the positive input and GND
selected as the negative input.
4. Calculate the offset characteristics, and store this value in non-volatile memory for use with
subsequent temperature sensor measurements.
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