c8051t617 Silicon Laboratories, c8051t617 Datasheet - Page 45

• Manufacturer Part Number: c8051t617
• Description: Mixed Signal Byte-programmable Eprom Mcu
• Manufacturer: Silicon Laboratories

5.5.
The temperature sensor transfer function is shown in Figure 5.2. The output voltage (V
input when the temperature sensor is selected by bits AMX0P4–0 in register AMX0P. Values for the Offset
and Slope parameters can be found in Table 5.1.
5.5.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature mea-
surements (see Table 5.1 for linearity specifications). For absolute temperature measurements, offset and/
or gain calibration is recommended. Typically a 1-point (offset) calibration includes the following steps:
Figure 5.3 shows the typical temperature sensor error assuming a 1-point calibration at 25 °C. Parame-
ters that affect ADC measurement, in particular the voltage reference value, will also affect temper-
ature measurement.
A single-point offset measurement of the temperature sensor is performed on each device during produc-
tion test. The registers TOFFH and TOFFL shown in SFR Definition 5.1 and SFR Definition 5.2 represent
the output of the ADC when reading the temperature sensor at 0 degrees Celsius, and using the internal
regulator as a voltage reference.
Temperature Sensor
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
Step 4. Calculate the offset characteristics, and store this value in non-volatile memory for use
and GND selected as the negative input.
with subsequent temperature sensor measurements.
Figure 5.2. Temperature Sensor Transfer Function
V
Temp
TEMP
C
=
= (V
(Slope
TEMP
x Temp
Rev. 0.3
- Offset) /
Temperature
C8051T610/1/2/3/4/5/6/7
C
) +
Offset
Slope
Offset
(V at 0 Celsius)
Slope
(V / deg C)
TEMP
) is the ADC
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