Inflow Current Bypass Circuit - Renesas M32R/ECU Series User Manual

11

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 wrap around 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 wrapping around
to the selected analog input. That way, the accuracy of the A-D conversion result is prevented from being deterio-
rated by extreme voltages.
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
Figure 11.4.1 Configuration of the Inflow Current Bypass Circuit
VCCE + 0.7 V or more
Unselected channel
Selected channel
Sensor input
Figure 11.4.2 Example of an Inflow Current Bypass Circuit where VCCE + 0.7 V or More is Applied
OFF
Fixed to GND level
ON
ON
External input
latched into
OFF
Assist circuit
Leakage current
generated
OFF
Leakage current
generated
ON
ON
OFF
11-41
11.4 Inflow Current Bypass Circuit
OFF
ON
OFF
Unaffected
by leakage
ON
Assist circuit
32180 Group User's Manual (Rev.1.0)
A-D Converters
To the internal logic
of the A-D Converter
To the internal logic
of the A-D Converter