C8051F93X Datasheet, PDF (87/330 Pages) Silicon Laboratories – Pipelined intstruction architecture executes 70 of instruction in 1 or 2 system clocks

C8051F93x-C8051F92x
5.6.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature
measurements (see Table 4.10 for linearity specifications). For absolute temperature measurements,
offset and/or gain calibration is recommended. Typically a 1-point (offset) 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 characteristics, and store this value in non-volatile memory for use
with subsequent temperature sensor measurements.
Figure 5.9 shows the typical temperature sensor error assuming a 1-point calibration at 25 °C.
Parameters that affect ADC measurement, in particular the voltage reference value, will also affect
temperature measurement.
A single-point offset measurement of the temperature sensor is performed on each device during
production test. The measurement is performed at 25 °C ±5 °C, using the ADC with the internal high speed
reference buffer selected as the Voltage Reference. The direct ADC result of the measurement is stored in
the SFR registers TOFFH and TOFFL, shown in SFR Definition 5.13 and SFR Definition 5.14.
5.00
4.00
3.00
2.00
1.00
0.00
-40.00
-1.00
-2.00
-3.00
-4.00
-5.00
-20.00
0.00
40.00
60.00
20.00
Temperature (degrees C)
5.00
4.00
3.00
2.00
1.00
0.00
80.00
-1.00
-2.00
-3.00
-4.00
-5.00
Figure 5.9. Temperature Sensor Error with 1-Point Calibration (V_REF = 1.68 V)
Rev. 1.3
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