Influences On Absolute Precision; Setting Range Of Analog Power Supply And Other Pins; Notes On Board Design - Renesas H8S/2368 Series Hardware Manual

16.7.3

Influences on Absolute Precision

Adding capacitance results in coupling with GND, and therefore noise in GND may adversely
affect absolute precision. 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 communicate with digital signals on the
mounting board, so acting as antennas.
16.7.4

Setting Range of Analog Power Supply and Other Pins

If conditions shown below are not met, the reliability of the device 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 ≤ AVn ≤ Vref.
• Relation between AVcc, AVss and Vcc, Vss
As the relationship between AVcc, AVss and Vcc, Vss, set AVcc ≥ Vcc and AVss = Vss. If
the A/D converter is not used, the AVcc and AVss pins must not be left open.
• Vref setting range
The reference voltage at the Vref pin should be set in the range Vref ≤ AVcc.
16.7.5

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 signals (AN0 to AN7, AN12, AN13),
analog reference power supply (Vref), and analog power supply (AVcc) by the analog ground
(AVss). Also, the analog ground (AVss) should be connected at one point to a stable digital
ground (Vss) on the board.
Rev. 2.00, 05/03, page 633 of 820