SH7261 datasheet(1065/1348 Pages) RENESAS

1065 / 1348 page

Section 22 A/D Converter (ADC)

Rev. 2.00 Sep. 07, 2007 Page 1033 of 1312

REJ09B0320-0200

22.7

Usage Notes

When using the A/D converter, note the following points.

22.7.1

Module Standby Mode Setting

Operation of the A/D converter can be disabled or enabled using the standby control register. The

initial setting is for operation of the A/D converter to be halted. Register access is enabled by

clearing module standby mode. For details, see section 27, Power-Down Modes.

22.7.2

Setting Analog Input Voltage

Permanent damage to the LSI may result if the following voltage ranges are exceeded.

1. Analog input range

During A/D conversion, voltages on the analog input pins ANn should not go beyond the

following range: AVss

≤ ANn ≤ AVcc (n = 0 to 7).

2. AVcc and AVss input voltages

Input voltages AVcc and AVss should be PVcc

− 0.3 V ≤ AVcc ≤ PVcc and AVss = PVss. Do

not leave the AVcc and AVss pins open when the A/D converter or D/A converter is not in use

and in software standby mode. When not in use, connect AVcc to the power supply (PVcc) and

AVss to the ground (PVss).

3. Setting range of AVref input voltage

Set the reference voltage range of the AVref pin as 3.0 V

≤ AVref ≤ AVcc.

22.7.3

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 signals (AN0 to AN7), analog reference

voltage (AVref), 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 (PVss) on the board.

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