Panasonic F77G, MN101C77C user manual Recommended Connection with A/D Converter

Models: F77G MN101C77C

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Chapter 15 A/D Converter

To maintain high precision of A/D conversion, following instructions on use of A/D con- verter should be strictly kept.

1.Input impedance R of A/D input pin should be under 500 k*1. And connect the external capacitor C (over 1000 pF, under 1 F)*1 between Vss and the A/D input pin.

2.Set the A/D conversion frequency depending on the time constant of R and C.

3.Changing the output level of the microcontroller or switching ON/OFF of the periph- eral added circuit while the A/D conversion is in progress may lower the precision of A/D conversion, for these may fluctuate the values of the analog input pin and the power pin. Check the waveform of the analog input pin before the system evaluation.

Equivalent circuit block that

microcontroller

outputs analog signal

 

 

 

 

R

 

 

 

 

 

 

A/D input pin

 

 

 

 

 

C

 

 

 

 

 

Vss

1 FC 1000 pF *1

 

 

 

 

 

 

*1 : That value is for reference.

as R500 k

 

 

 

 

 

 

Recommended Connection with A/D Converter

Operation XV - 17

Page 491
Image 491
Panasonic F77G, MN101C77C user manual Recommended Connection with A/D Converter