HCS08 datasheet(121/316 Pages) NXP

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Chapter 9 Analog-to-Digital Converter (S08ADCV1)

MC9S08SG8 MCU Series Data Sheet, Rev. 8

Freescale Semiconductor

121

For temperature calculations, use the VTEMP25 and m values from the ADC Electricals table.

In application code, the user reads the temperature sensor channel, calculates VTEMP, and compares to

VTEMP25. If VTEMP is greater than VTEMP25, the cold slope value is applied in Equation 9-1. If VTEMP is

less than VTEMP25, the hot slope value is applied in Equation 9-1. 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 Equation 9-1 as detailed above and then determine if the

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.

Figure 9-1 shows the MC9S08SG8 block diagram with the ADC module highlighted.

HCS08 Folha de dados(PDF) 121 Page - NXP Semiconductors