210
CHAPTER 12 10-BIT A/D CONVERTER (
µ
PD780034AS SUBSERIES)
Preliminary User’s Manual U16035EJ1V0UM
(12) AV
DD
pin
The AV
DD
pin
is the analog circuit power supply pin. It supplies power to the input circuits of the ANI0 to ANI3
pins.
Therefore, be sure to apply the same potential as V
DD0
to
this pin even for applications designed to switch to a
backup battery for power supply.
Figure 12-20. AV
DD
Pin Connection
Main power supply
Capacitor
for backup
AV
REF
V
DD0
AV
SS
AV
DD
V
SS0
(13) AV
REF
pin
Connect a capacitor to the AVREF pin
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
REF
pin
becomes unstable, causing the
accuracy of the A/D conversion to drop. To prevent this, also connect a capacitor to the AV
REF
pin
.
Figure 12-21 shows an example of connecting a capacitor.
Figure 12-21. Example of Connecting Capacitor to AV
REF
Pin
AV
REF
AV
SS
C
2
C
1
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.
