H8SLASH3021 datasheet(459/712 Pages) RENESAS

459 / 712 page

13. A/D Converter

Rev.2.00 Mar. 22, 2007 Page 435 of 684

REJ09B0352-0200

13.5

Interrupts

The A/D converter generates an interrupt (ADI) at the end of A/D conversion. The ADI interrupt

request can be enabled or disabled by the ADIE bit in ADCSR.

13.6

Usage Notes

The following points should be noted when using the A/D converter.

Setting Range of Analog Power Supply and Other Pins:

(1) Analog input voltage range

The voltage applied to analog input pins AN

0 to AN7 during A/D conversion should be in the

range AV

SS ≤ ANn

≤ AV

CC.

(2) Relation between AV

CC, AVSS and VCC, VSS

As the relationship between AV

CC, AVSS and VCC, VSS, set AVSS = VSS.

If the A/D converter is

not used, the AV

CC and AVSS pins must on no account be left open.

If conditions (1) and (2) above are not met, the reliability of the device may be adversely affected.

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 (AN

0 to AN7), and analog

power supply and reference voltage (AV

CC) by the analog ground (AVSS).

Also, the analog ground

(AV

SS) should be connected at one point to a stable digital ground (VSS) on the board.

Notes on Noise Countermeasures: A protection circuit connected to prevent damage due to an

abnormal voltage such as an excessive surge at the analog input pins (AN

0 to AN7) and analog

power supply (AV

) should be connected between AVCC and AVSS as shown in figure 13.7.

Also, the bypass capacitors connected to AV

CC and the filter capacitor connected to AN0 to AN7

must be connected to AV

SS.

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