Chapter 6 A/D Conversion Functions

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 1 with an external capacitor, C, that is minimum 1,000pF and maximum 1µF1.

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

Microcomputer

R

 

 

A/D input pin

 

C

1

Vss

1 FC1000pF

 

where R500kΩ

 

1 These values are reference values.

Figure 6-2-2 Recommended Circuit When Using A/D Conversion

116 A/D Converter Control Registers

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Image 130
Panasonic MN101C00 user manual Recommended Circuit When Using A/D Conversion