SH7720 Datasheet, PDF (1011/1524 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

Section 27 A/D Converter
27.7.4 Influence to Absolute Accuracy
By adding capacitance, absolute accuracy may be degraded if noise is on GND because there is
coupling with GND. Therefore, connect electrically stable GND such as AVss to prevent absolute
accuracy from being degraded.
A filter circuit must not interfere with digital signals, or must not be an antenna on a mounting
board.
Output impedance of sensor
to 5 kΩ
Sensor input
Lowpass
filter
(C = 0.1µF)
This LSI
C_in =
15 pF
Equivalent circuit
of A/D converter
3 kΩ
20 pF
Figure 27.8 Analog Input Circuit Example
27.7.5 Setting Analog Input Voltage
Operating the chip in excess of the following voltage range may result in damage to chip
reliability.
During A/D conversion, the voltages (VANn) input to the analog input pins ANn should be in the
range AV_SS ≤ VANn ≤ AV_CC (n = 0 to 3).
27.7.6 Notes on Board Design
In designing a board, separate digital circuits and analog circuits. Do not intersect or locate closely
signal lines of a digital circuit and an analog circuit. An analog circuit may malfunction due to
induction, thus affecting A/D conversion values. Separate analog input pins (AN0 to AN3) and the
analog power voltage (AVcc) from digital circuits with analog ground (AVss). Connect analog
ground (AVss) to one point of stable ground (Vss) on the board.
Rev. 3.00 Jan. 18, 2008 Page 949 of 1458
REJ09B0033-0300