MB89P935C Fujitsu Microelectronics, Inc., MB89P935C Datasheet - Page 32

• Manufacturer Part Number: MB89P935C
• Description: 8-bit Proprietary Microcontroller
• Manufacturer: Fujitsu Microelectronics, Inc.

32
MB89930C Series
(3) Notes on Using A/D Converter
• Input impedance of the analog input pins
• Error
The A/D converter used for the MB89930C series contains a sample hold circuit as illustrated below to fetch
analog input voltage into the sample hold capacitor for 16 instruction cycles after activation A/D conversion.
For this reason, if the output impedance of the external circuit for the analog input is high, analog input voltage
might not stabilize within the analog input sampling period. Therefore, it is recommended to keep the output
impedance of the external circuit low (below 4k Ω).
Note that if the impedance cannot be kept low, it is recommended to connect an external capacitor of about
0.1 µ F for the analog input pin.
The smaller the |AVR - AV
If the analog input
impedance is higher
than 4 kΩ, it is
recommended to
connect an external
capacitor of approx.
0.1 µF.
Analog Input Circuit Model
SS
Analog input pin
|, the greater the error would become relatively.
Analog channel selector
Sample hold circuit
Close for 16 instruction cycles after
activating A/D conversion.
R
C
Comparator