MB89538APFM View Datasheet(PDF) - Fujitsu

Part Name

Description

Manufacturer

MB89538APFM

F2MC-8L MB89530A Series / 8-bit Original Microcontroller CMOS

Fujitsu 

MB89530A Series

(4) Precautionary Information

• Input Impedance of Analog Input Pins

The A/D converter of MB89530A has a sample & hold circuit as shown below, which uses a sample-and-hold

capacitor to obtain the voltage at the analog input pin for 8 instruction cycles following the start of A/D conversion.

For this reason if the external circuits providing the analog input signal have high output impedance, the analog

input voltage may not stabilize within the analog input sampling time. It is therefore recommended that the output

impedance of external circuits be reduced to 10 kΩ or less.

• MB89535A/537A/537AC/538A/538AC Analog Input Equivalent Circuit

Sample-and-hold circuit

Analog input pin

C = 45 pF

Compara-

tor

If analog input impedance is

10 kΩ or more, the use of a

capacitor of approximately

0.1 µF is recommended.

R = 2.2 kΩ

Closes 8 instruction cycles

after the start of A/D conversion

Analog channel selector

• MB89P538 and MB89PV530 Analog Input Equivalent Circuit

Analog input pin

If analog input impedance is

10 kΩ or more, the use of a

capacitor of approximately

0.1 µF is recommended.

Sample-and-hold circuit

C = 64 pF

Compara-

tor

R = 3 kΩ

Closes 8 instruction cycles

after the start of A/D conversion

Analog channel selector

• MB89F538 Analog Input Equivalent Circuit

Analog input pin

If analog input impedance is

10 kΩ or more, the use of a

capacitor of approximately

0.1 µF is recommended.

Sample-and-hold circuit

C = 30 pF

Compara-

tor

R = 3.2 kΩ

Closes 8 instruction cycles

after the start of A/D conversion

Analog channel selector

• About error

The smaller the absolute value |AVR - AVss| is, the greater the relative error becomes.

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