HD6412240 RENESAS [Renesas Technology Corp], HD6412240 Datasheet - Page 562

• Manufacturer Part Number: HD6412240
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family / H8S/2200 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 14 A/D Converter
Notes on Board Design
In board design, digital circuitry and analog circuitry should be as mutually isolated as possible,
and layout in which digital circuit signal lines and analog circuit signal lines cross or are in close
proximity should be avoided as far as possible. Failure to do so may result in incorrect operation
of the analog circuitry due to inductance, adversely affecting A/D conversion values.
Also, digital circuitry must be isolated from the analog input signals (AN0 to AN3), analog
reference power supply (V
the analog ground (AV
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 AN3) and analog reference power supply (V
connected between AV
Also, the bypass capacitors connected to AV
to AN3 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 AN3) 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.
Rev.3.00 Mar. 26, 2007 Page 520 of 772
REJ09B0355-0300
in
), an error will arise in the analog input pin voltage. Careful consideration is therefore required
SS
CC
) should be connected at one point to a stable digital ground (V
and AV
ref
), and analog power supply (AV
SS
SS
.
as shown in figure 14.7.
CC
and V
ref
and the filter capacitor connected to AN0
CC
) by the analog ground (AV
ref
) should be
SS
) on the
SS
). Also,