C8051F388 Datasheet, PDF (44/285 Pages) –

C8051F388/9/A/B
6.2. Temperature Sensor
The typical temperature sensor transfer function is shown in Figure 6.2. The output voltage (V_TEMP) is the
positive ADC input when the temperature sensor is selected by bits AMX0P5-0 in register AMX0P.
Figure 6.2. Typical Temperature Sensor Transfer Function
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature mea-
surements (see Table 5.10, “ADC0 Electrical Characteristics,” on page 39 for linearity specifications). For
absolute temperature measurements, gain and/or offset calibration is recommended. Typically a 1-point
calibration includes the following steps:
Step 1. Control/measure the ambient temperature (this temperature must be known).
Step 2. Power the device, and delay for a few seconds to allow for self-heating.
Step 3. Perform an ADC conversion with the temperature sensor selected as the positive input
and GND selected as the negative input.
Step 4. Calculate the offset and/or gain characteristics, and store these values in non-volatile
memory for use with subsequent temperature sensor measurements.
Figure 6.3 shows the typical temperature sensor error assuming a 1-point calibration at 25 °C. Note that
parameters which affect ADC measurement, in particular the voltage reference value, will also
affect temperature measurement.
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