Example Of Usage Of A/D Converter - Oki ML63611 User Manual

16.3.3 Example of Usage of A/D Converter

The method to perform A/D conversion of sensor values by using Counter A reference mode and Counter B
reference mode is explained by taking temperature measurement with a thermistor as an example.
Figure 16-8 shows the layout of RC oscillation circuit.
Figure 16-8 Layout of RC Oscillation Circuit of a Thermistor Using CROSC0
Figure 16-9 shows the temperature characteristics of the resistance value, RT0, of the thermistor.
Temperature T
Figure 16-9 Temperature Characteristics
of Thermistor
RT0 is expressed as a function of temperature T as
RT0 = f (T)
Figure 16-10 shows the ideal characteristics of A/D conversion taking RT0 as an analog quantity and it is ideal
that the A/D conversion value nT0 depends solely on RT0. Assuming that nT0 is proportional to RT0, the value
of nT0 is expressed by temperature T and the proportionality constant K as
nT0 = K • RT0 = K • f (T)
OPTION A (C): 1.5 V (3.0 V), Without regulator
circuit for LCD bias
Reference
resistance
RS0
Thermistor
RT0
CS0
RI0
RT0 = f(T)
16 – 11
Chapter 16 A/D Converter (ADC)
ML63611 series
RS0
RT0
CS0
IN0
RT0
Figure 16-10 A/D Conversion
Characteristics
(Ideal characteristics when nT0 is
proportional to RT0)
- - - - -
OPTION B (D): 1.5 V (3.0 V), With regulator
ML63611 User's Manual
nT0 = K • RT0
= K • f(T)
equation (a)
circuit for LCD bias