Influences On Absolute Accuracy; Setting Range Of Analog Power Supply And Other Pins; Notes On Board Design - Renesas H8S/2100 Series Hardware Manual

Section 22 A/D Converter
22.7.3

Influences on Absolute Accuracy

Adding capacitance results in coupling with GND, and therefore noise in GND may adversely
affect the absolute accuracy. Be sure to make the connection to an electrically stable GND such as
AVss.
Care is also required to insure that filter circuits do not interfere with digital signals on the
mounting board, so acting as antennas.
22.7.4

Setting Range of Analog Power Supply and Other Pins

If conditions shown below are not met, the reliability of this LSI may be adversely affected.
•
Analog input voltage range
The voltage applied to analog input pins (AN0 to AN15) during A/D conversion should be in
the range AVss ≤ ANn ≤ AVref (n = 0 to 15).
• Relation between AVcc, AVss and Vcc, Vss
As the relationship between AVcc, AVss and Vcc, Vss, set AVcc = Vcc ±0.3 V and AVss =
Vss. If the A/D converter is not used, set AVcc = Vcc and AVss = Vss.
• AVref pin range
The reference voltage of the AVref pin should be in the range AVref ≤ AVcc.
22.7.5

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 pins (AN0 to AN15), analog reference voltage
(AVref), and analog power supply voltage (AVcc) by the analog ground (AVss). Also, the analog
ground (AVss) should be connected at one point to a stable ground (Vss) on the board.
Rev. 1.00 Apr. 28, 2008 Page 742 of 994
REJ09B0452-0100