SH7280 Datasheet, PDF (1038/1726 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine family

Section 20 A/D Converter (ADC)
20.7.5 Notes on Noise Countermeasures
To prevent damage due to an abnormal voltage, such as an excessive surge at the analog input pins
(AN0 to AN11) and analog reference power supply (AVREF), a protection circuit should be
connected between the AVcc and AVss, as shown in figure 20.14. The bypass capacitors
connected to AVREF and the filter capacitor connected to ANn should be connected to the AVss.
If a filter capacitor is connected as shown in figure 20.14, the input currents at the analog input pin
(ANn) are averaged, and an error may occur. Careful consideration is therefore required when
deciding the circuit constants.
4.5 V to 5.5 V
GND
Analog input pins
(channels 0 to 11)
10 µF
0.1 µF
0.1 µF
TBD Ω
TBD µF
AVcc
AVss
AVREF
This LSI
AVREFVSS
AN0 to AN11
Figure 20.14 Example of Analog Input Pin Protection Circuit
Rev. 1.00 Jun. 26, 2008 Page 1008 of 1692
REJ09B0393-0100