mc9s08ac32 Freescale Semiconductor, Inc, mc9s08ac32 Datasheet - Page 137

• Manufacturer Part Number: mc9s08ac32
• Description: Hcs08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

9.2.3
The ADC module includes a temperature sensor whose output is connected to one of the ADC analog
channel inputs.
where:
For temperature calculations, use the V
In application code, the user reads the temperature sensor channel, calculates V
V
less than V
To improve accuracy , calibrate the bandgap voltage reference and temperature sensor.
Calibrating at 25 °C will improve accuracy to 4.5 °C.
Calibration at 3 points, -40 °C, 25 °C, and 125 °C will improve accuracy to 2.5 °C. Once calibration has
been completed, the user will need to calculate the slope for both hot and cold. In application code, the
user would then calculate the temperature using
temperature is above or below 25 °C. Once determined if the temperature is above or below 25 °C, the user
can recalculate the temperature using the hot or cold slope value obtained during calibration.
For more information on using the temperature sensor, consult AN3031.
Freescale Semiconductor
TEMP25
— V
— V
— m is the hot or cold voltage versus temperature slope in V/°C.
. If V
TEMP25
Temperature Sensor
TEMP
TEMP25
TEMP
Equation 9-1
is the voltage of the temperature sensor channel at the ambient temperature.
the hot slope value is applied in
is greater than V
is the voltage of the temperature sensor channel at 25°C.
provides an approximate transfer function of the temperature sensor.
Temp = 25 - ((V
MC9S08AC60 Series Data Sheet, Rev. 2
TEMP25
TEMP25
the cold slope value is applied in
TEMP
and m values from the ADC Electricals table.
Equation 9-1
-V
Equation
TEMP25
) ÷ m)
9-1.
as detailed above and then determine if the
Chapter 9 Analog-to-Digital Converter (S08ADC10V1)
Equation
TEMP
, and compares to
9-1. If V
Eqn. 9-1
TEMP
137
is