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6. Note on Noise: To prevent damage from surges and other abnormal voltages at the analog
input pins (AN
to AN
0
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like the one in figure 15-7 between AV
AV
and V
and the filter capacitors connected to AN
CC
REF
AV
. If filter capacitors like the ones in figure 15-7 are connected, the voltage values input to
SS
the analog input pins (AN
also occur if A/D conversion is frequently performed in scan mode so that the current that
charges and discharges the capacitor in the sample-and-hold circuit of the A/D converter
becomes greater than that input to the analog input pins via input impedance Rin. The circuit
constants should therefore be selected carefully.
Rin
*1
*1
Notes: 1. Numeric values are approximate.
10 µF
2. Rin: input impedance
Figure 15-7 Example of Analog Input Protection Circuit
) and analog reference voltage pin (V
7
and AV
CC
to AN
) will be smoothed, which may give rise to error. Error can
0
7
100 Ω
*2
0.1 µF
0.01 µF
540
), connect a protection circuit
REF
. The bypass capacitors connected to
SS
to AN
must be connected to
0
7
AV
CC
V
REF
AN
to AN
0
7
AV
SS
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