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CHAPTER 12 8-BIT A/D CONVERTER (
µ
PD780344, 780344Y SUBSERIES)
User’s Manual U15798EJ2V0UD
(13) AV
DD
and AV
SS
pins
Connect a capacitor between the AV
DD
and AV
SS
pins to minimize conversion errors due to noise. If an A/D
conversion operation has been stopped and then is started, the voltage applied to the AV
DD
and AV
SS
pins
becomes unstable, causing the accuracy of the A/D conversion to drop. To prevent this, also connect a capacitor
between the AV
DD
and AV
SS
pins.
Figure 12-16 shows an example of connecting a capacitor.
Figure 12-16. Example of Connecting Capacitor to AV
DD
Pin
Remark
C1: 4.7
µ
F to 10
µ
F (reference value)
C2: 0.01
µ
F to 0.1
µ
F (reference value)
Connect C2 as close to the pin as possible.
(14) AV
DD
pin
The AV
DD
pin supplies power to the analog circuit. It also supplies power to the input circuit of ANI0 to ANI7.
Therefore, apply the same potential as that of the V
DD0
or V
DD1
pin to this pin, as shown in Figure 12-17, in an
application where a backup power supply is used.
Figure 12-17. Processing of AV
DD
Pin
C1
C2
AV
DD
AV
SS
Main power supply
Backup capacitor
V
DD0
or V
DD1
AV
DD
V
SS0
or V
SS1
AV
SS