p2125vps20 Renesas Electronics Corporation., p2125vps20 Datasheet - Page 490

• Manufacturer Part Number: p2125vps20
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 17 A/D Converter
17.7.3
If conditions shown below are not met, the reliability of this LSI may be adversely affected.
•
• Relation between AVCC, VSS and VCC, VSS
17.7.4
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 AN7) 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.
17.7.5
A protection circuit connected to prevent damage of the analog input pins (AN0 to AN7) due to an
abnormal voltage such as an excessive surge should be connected between AVCC and AVSS, as
shown in figure 17.7. Also, the bypass capacitors connected to AVCC and the filter capacitors
connected to AN0 to AN7 must be connected to AVSS.
If a filter capacitor is connected, the input currents at the analog input pins (AN0 to AN7) are
averaged, and so an error may arise. Also, when A/D conversion is performed frequently, as in
scan mode, if the current charged and discharged by the capacitance of the sample-and-hold circuit
in the A/D converter exceeds the current input via the input impedance (R
the analog input pin voltage. Careful consideration is therefore required when deciding the circuit
constants.
Rev. 1.00 Sep. 21, 2006 Page 452 of 658
REJ09B0310-0100
The voltage applied to analog input pin ANn during A/D conversion should be in the range
AVSS ≤ ANn ≤ AVCC (n = 0 to 7).
For the relationship between AVCC, AVSS and VCC, VSS, set AVSS = VSS, but AVCC =
VCC is not necessary and which one is greater does not matter. Even when the A/D converter
is not used, the ACC and AVSS pins must on no account be left open.
Analog input voltage range
Setting Range of Analog Power Supply and Other Pins
Notes on Board Design
Notes on Noise Countermeasures
in
), an error will arise in