C8051F850-B-GM Datasheet, PDF (87/290 Pages) Silicon Laboratories – Low-Cost 8-bit MCU Family with up to 8 kB of Flash

C8051F85x/86x
14.9. Temperature Sensor
An on-chip temperature sensor is included, 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 14.8. 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. 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 the electrical
specification tables for the slope and offset parameters of the temperature sensor.
V_TEMP = (Slope x Temp_C) + Offset
Temp_C = (V_TEMP - Offset) / Slope
Slope (V / deg C)
Offset (V at 0 Celsius)
Temperature
Figure 14.8. Temperature Sensor Transfer Function
14.9.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature
measurements. 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 ADC input.
4. Calculate the offset characteristics, and store this value in non-volatile memory for use with subsequent
temperature sensor measurements.
90
Preliminary Rev 0.6