Hitachi SH7032 - A;D Converter Usage Notes; Handling of Analog Input Pins; Setting Analog Input Voltage

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14.7 A/D Converter Usage Notes
When using the A/D converter, note the points listed in section 14.7.1 below.
14.7.1 Setting Analog Input Voltage
• Analog Input Voltage Range: During A/D conversion, the voltages input to the analog input
pins ANn should be in the range AV
SS
≤ ANn ≤ AV
ref
.
• Relationships of AV
CC
and AV
SS
to V
CC
and V
SS
: AV
CC
, AV
SS
, V
CC
and V
SS
should be
related as follows: AV
CC
= V
CC
± 10% and AV
SS
= V
SS
. If the A/D converter is not used, set
AV
CC
= V
CC
and AV
SS
= V
SS
.
• AV
ref
Input Range: The analog reference voltage input at the AV
ref
pin should be in the range
AV
ref
≤ AV
CC
. If the converter is not used, set AV
ref
= V
CC
.
• When the converter is neither in use nor in standby mode, connect AV
CC
and AV
ref
to the
power voltage (V
CC
).
14.7.2 Handling of Analog Input Pins
To prevent damage from voltage surges at the analog input pins (AN0–AN7), connect an input
protection circuit like the one shown in figure 14.8. The circuit shown also includes an RC filter to
prevent errors due to noise. This circuit is shown as an example: The circuit constants should be
selected according to actual application conditions. Table 14.5 list the analog input pin
specifications and figure 14.9 shows an equivalent circuit diagram of the analog input ports.
0.01 µF
10 µF

AV
CC
AV
ref
AN0–AN7
AV
SS
SuperH microcomputer
**
100 Ω
0.1 µF
Note: *
Figure 14.8 Example of Analog Input Protection Circuit