HD6412340 HITACHI [Hitachi Semiconductor], HD6412340 Datasheet - Page 533

• Manufacturer Part Number: HD6412340
• Description: H8S/2345 F-ZTAT Hardware Manual
• Manufacturer: HITACHI [Hitachi Semiconductor]

Also, digital circuitry must be isolated from the analog input signals (AN0 to AN7), analog
reference power supply (V
Also, the analog ground (AV
on the board.
Notes on Noise Countermeasures: A protection circuit connected to prevent damage due to an
abnormal voltage such as an excessive surge at the analog input pins (AN0 to AN7) and analog
reference power supply (V
14.7.
Also, the bypass capacitors connected to AV
to AN7 must be connected to AV
If a filter capacitor is connected as shown in figure 14.7, the input currents at the analog input pins
(AN0 to AN7) are averaged, and so an error may arise. Also, when A/D conversion is performed
frequently, as in scan mode, if the current charged and discharged by the capacitance of the
sample-and-hold circuit in the A/D converter exceeds the current input via the input impedance
(R
when deciding the circuit constants.
520
Notes:
in
), an error will arise in the analog input pin voltage. Careful consideration is therefore required
*
1
Values are reference values.
1.
2. R
*
1
10 F
in
: Input impedance
Figure 14.7 Example of Analog Input Protection Circuit
R
ref
ref
in
*
), and analog power supply (AV
) should be connected between AV
SS
2
) should be connected at one point to a stable digital ground (V
0.01 F
SS
.
100
0.1 F
CC
and V
ref
AV
V
AN0 to AN7
AV
and the filter capacitor connected to AN0
ref
CC
SS
CC
) by the analog ground (AV
CC
and AV
SS
as shown in figure
SS
).
SS
)