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Chapter 19
19.5 Cautions
(1)
(2)
(3)
Figure 19-12
(4)
694
When A/D Converter is not used
When the A/D Converter is not used, the power consumption can be reduced
by clearing the ADAnCE bit and the ADAnPS bit of the ADAnM0 register to 0.
Input range of ANInm pins
Input the voltage within the specified range to the ANInm pins. If a voltage
equal to or higher than AV
range of the absolute maximum ratings) is input to any of these pins, the
conversion value of that channel is undefined and the conversion value of the
other channels may also be affected.
Countermeasures against noise
To maintain the 10-bit resolution, the ANInm pins must be effectively protected
from noise. The influence of noise increases as the output impedance of the
analog input source becomes higher. To lower the noise, connecting an
external capacitor as shown in Figure 19-12 is recommended.
C = 100 to 1,000 pF
Processing of analog input pin
Alternate I/O
The analog input pins ANInm function alternately as port pins. Changing the
digital input/output function (PMCn and PMn; n = 2, 7 or 12) or changing the
level of one or more output ports (Pnm; n = 2, 7 or 12; m = 0 up to 15) while
ADA0CE bit = 1 could degrade the conversion accuracy.
For the output port the potential degradation increases with the driven total
output current. Also the conversion resolution may drop if the output current
fluctuates due to the effect of the external circuit connected to the port pins.
User's Manual U18743EE1V2UM00
or equal to or lower than AV
REF
V
DD
AV
REF
ANI0
to ANIn
AV
SS
V
SS
A/D Converter (ADC)
(even within the
SS
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