Influences On Absolute Accuracy; Setting Range Of Analog Power Supply And Other Pins; Notes On Board Design - Renesas H8SX/1500 Series Hardware Manual

Section 15 A/D Converter
15.7.3

Influences on Absolute Accuracy

Adding capacitance results in coupling with GND, and therefore noise in GND may adversely
affect absolute accuracy. Be sure to make the connection to an electrically stable GND such as
AVss.
Care is also required to insure that digital signals on the board do not interfere with filter circuits
and filter circuits do not act as antennas.
15.7.4

Setting Range of Analog Power Supply and Other Pins

If the conditions shown below are not met, the reliability of the LSI may be adversely affected.
• Analog input voltage range
The voltage applied to analog input pin ANn during A/D conversion should be in the range
AVss ≤ V ≤ AVcc0 and AVss ≤ V
AN
• Relation between AVcc0, AVcc1, AVss and Vcc, Vss
As the relationship between AVcc0, AVcc1, AVss and Vcc, Vss, set AVcc0 = Vcc ± 0.3 V,
AVcc1 = Vcc ± 0.3 V, and AVss = Vss. If the A/D converter is not used, set AVcc0 = Vcc,
AVcc1 = Vcc, and AVss = Vss.
15.7.5

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.
Digital circuitry must be isolated from the analog input pins (AN0 to AN15) and analog power
supply (AVcc0 and AVcc1) 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. 3.00 Mar. 14, 2006 Page 564 of 804
REJ09B0104-0300
≤ AVcc1.
AN