h8s-2628 Renesas Electronics Corporation., h8s-2628 Datasheet - Page 503

• Manufacturer Part Number: h8s-2628
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

17.7.4
If the conditions below are not met, the reliability of the device may be adversely affected.
17.7.5
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 (AN15 to AN0) 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.
17.7.6
A protection circuit should be connected in order to prevent damage due to abnormal voltage, such
as an excessive surge at the analog input pins (AN15 to AN0), between AVcc and AVss, as shown
in figure 17.7. Also, the bypass capacitors connected to AVcc and the filter capacitor connected to
AN15 to AN0 must be connected to AVss.
If a filter capacitor is connected, the input currents at the analog input pins (AN15 to AN0) 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 circuit
constants.
Analog input voltage range
The voltage applied to analog input pin ANn during A/D conversion should be in the range
AVss
Relationship between AVcc, AVss and Vcc, Vss
Set AVss = Vss as the relationship between AVcc, AVss and Vcc, Vss. If the A/D converter is
not used, the AVcc and AVss pins must not be left open.
Setting range of the Vref pin
The reference voltage set by the Vref pin should be in the range Vref
Range of Analog Power Supply and Other Pin Settings
Notes on Board Design
Notes on Noise Countermeasures
VNn
AVcc.
Rev. 3.00 Oct 04, 2005 page 463 of 598
Section 17 A/D Converter
in
AVcc.
), an error will arise in
REJ09B0155-0300