MB90330A_9E Datasheet, PDF (59/72 Pages) Fujitsu Component Limited. – 16-bit microcontrollers

MB90330A Series
Notes :
• About the external impedance of the analog input and its sampling time
• A/D converter with sample and hold circuit. If the external impedance is too high to keep sufficient sampling
time, the analog voltage charged to the internal sample and hold capacitor is insufficient, adversely affecting
A/D conversion precision.
• Analog input circuit model
R
Analog input
C
During sampling : ON
Note : The values are reference values.
MB90333A
MB90F334A
MB90F335A
MB90V330A
Comparator
R
1.9 kΩ (Max)
1.9 kΩ (Max)
1.9 kΩ (Max)
1.9 kΩ (Max)
C
32.3 pF (Max)
25.0 pF (Max)
25.0 pF (Max)
32.3 pF (Max)
• To satisfy the A/D conversion precision standard, consider the relationship between the external impedance
and minimum sampling time and either adjust the resistor value and operating frequency or decrease the
external impedance so that the sampling time is longer than the minimum value.
• The relationship between the external impedance and minimum sampling time
(External impedance = 0 kΩ to 100 kΩ)
(External impedance = 0 kΩ to 20 kΩ)
100
90
80
70
60
50
40
30
20
10
0
0
MB90333A/
MB90V330A
MB90F334A
MB90F335A
5 10 15 20 25 30 35
Minimum sampling time [μs]
MB90333A/
MB90V330A
20
18
16
MB90F334A
MB90F335A
14
12
10
8
6
4
2
0
012345678
Minimum sampling time [μs]
• If the sampling time cannot be sufficient, connect a capacitor of about 0.1 μF to the analog input pin.
• About errors
As |AVRH| becomes smaller, values of relative errors grow larger.
DS07-13734-9E
59