Datasheet

Section 18 A/D Converter
Page 1090 of 1408 R01UH0309EJ0500 Rev. 5.00
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
18.7.6 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
AN ≤ Vref.
• Relation between AVss and Vss, and AVcc and Vcc
As the relationship between AVss and Vss, set AVss = Vss. If the A/D converter is not used,
set AVcc = Vcc and AVss = Vss.
• Vref setting range
The reference voltage at the Vref pin should be set in the range Vref ≤ AVcc.
18.7.7 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*), 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 ground (Vss) on the board.
Note: * In the H8S/2454 group, only AN0 to AN7, AN12, and AN13 are available as analog
input pins.