SH7050 Datasheet, PDF (477/841 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH RISC engine Family/

Section 14 A/D Converter
5. 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 (ANn) and analog reference voltage (AV_ref) should be
connected between AV_CC and AV_SS as shown in figure 14.8.
Also, the bypass capacitors connected to AV_CC and AV_ref and the filter capacitor connected to
ANn must be connected to AV_SS. If a filter capacitor is connected as shown in figure 14.8, the
input currents at the analog input pins (ANn) are averaged, and so an error may arise. Careful
consideration is therefore required when deciding the circuit constants.
*1 *1
R_in^*2
100 Ω
0.1 µF
AV_CC
AV_ref
AN0–AN15
AV_SS
Notes: 1.
10 µF
0.01 µF
SH7050
2. R_in: Input impedance
Figure 14.8 Example of Analog Input Pin Protection Circuit
Table 14.5 Analog Pin Specifications
Item
Analog input capacitance
Permissible signal source impedance
Min
Max
Unit
—
20
pF
—
3
kΩ
Rev. 5.00 Jan 06, 2006 page 457 of 818
REJ09B0273-0500