32186 datasheet(543/1032 Pages) RENESAS

543 / 1032 page

A/D CONVERTER

11-45

32185/32186 Group Hardware Manual

Rev.1.10 REJ09B0235-0110 May 15, 07

11.4 Inflow Current Bypass Circuit

If when the A/D Converter is A/D converting a selected analog input an overvoltage exceeding the

converter’s absolute maximum rating is applied to any unselected analog input, the selector for the

unselected analog input is inadvertently turned on by that overvoltage. This causes current to leak to the

selected analog input, and the accuracy of the A/D conversion result is thereby deteriorated.

The Inflow Current Bypass Circuit fixes the internal signals of unselected analog inputs to the GND level, so

that when an overvoltage is applied, this circuit lets the current flow into the GND and prevents it from leaking

to the selected analog input. That way, the accuracy of the A/D conversion result is prevented from being

deteriorated by overvoltages.

This circuit is always active while the A/D Converter is operating, and does not need to be controlled in software.

Unselected

channel

Selected

channel

To the internal logic

of the A/D Converter

OFF

Fixed to GND level

External input

latched into

Assist circuit

Figure 11.4.1 Configuration of the Inflow Current Bypass Circuit

Figure 11.4.2 Example of an Inflow Current Bypass Circuit where AVCC0 + 0.7 V or More is Applied

Unselected channel

Selected channel

To the internal logic

of the A/D Converter

OFF

Assist circuit

AVCC0 + 0.7 V or more

Leakage current

generated

Sensor input

Leakage current

generated

Unaffected

by leakage

32186 Datasheet(PDF) 543 Page - Renesas Technology Corp