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Chapter 6 A/D Conversion Functions
116
A/D Converter Control Registers
The following items must be implemented to maintain the accuracy of the
A/D converter:
1. Use a maximum input pin impedance, R, of 500kΩ
capacitor, C, that is minimum 1,000pF and maximum 1µF
2. Take the RC time into consideration when setting the A/D conversion
interval.
3. Changing the output level of the microcomputer or switching peripheral
circuitry on or off when the A/D converter is in use may cause the
analog input pin or current pin to fluctuate resulting in a loss of
precision. During setup and evaluation, verify the waveform of the
analog input pin.
Equivalent circuit of
analog signal output
1 F C 1000pF
where R 500k
Figure 6-2-2 Recommended Circuit When Using A/D Conversion
R
C
Vss
1
1 These values are reference values.
1
with an external
1
.
Microcomputer
A/D input pin
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