mb95f204h Fujitsu Microelectronics, Inc., mb95f204h Datasheet - Page 55

• Manufacturer Part Number: mb95f204h
• Description: F2mc-8fx Mb95200h/210h Series
• Manufacturer: Fujitsu Microelectronics, Inc.

DS07-12623-1E
(2) Notes on Using the A/D Converter
• External impedance of analog input and its sampling time
• A/D conversion error
• The A/D converter has a sample and hold circuit. If the external impedance is too high to keep sufficient
As |V
sampling time, the analog voltage charged to the internal sample and hold capacitor is insufficient, adversely
affecting A/D conversion precision. Therefore, to satisfy the A/D conversion precision standard, considering
the relationship between the external impedance and minimum sampling time, either adjust the register value
and operating frequency or decrease the external impedance so that the sampling time is longer than the
minimum value. In addition, if sufficient sampling time cannot be secured, connect a capacitor of about 0.1 µF
to the analog input pin.
CC
Analog input equivalent circuit
Note: The values are reference values.
Relationship between external impedance and minimum sampling time
− V
Analog input
100
SS
90
80
70
60
50
40
30
20
10
0
| decreases, the A/D conversion error increases proportionately.
0
[External impedance = 0 kΩ to 100 kΩ]
2
Minimum sampling time [µs]
(V
CC
4
> = 4.5 V)
6
(V
4.5 V
4.0 V
8
CC
R
During sampling: ON
> = 4.0 V)
< =
< =
10
V
V
CC
CC
< =
<
5.5 V : R
4.5 V : R
12
C
14
~ ~
~ ~
1.95 kΩ (max), C
8.98 kΩ (max), C
Comparator
MB95200H/210H Series
20
18
16
14
12
10
8
6
4
2
0
0
[External impedance = 0 kΩ to 20 kΩ]
~ ~
~ ~
(V
17 pF (max)
17 pF (max)
Minimum sampling time [µs]
CC
> = 4.5 V)
1
2
(V
CC
> = 4.0 V)
3
4
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