7480 datasheet(164/337 Pages) RENESAS

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7480 Group and 7481 Group User's Manual

1-147

HARDWARE

1.15.5 Notes on Usage

Pay attention to the following notes when the A-D converter is used.

The comparator consists of a capacitive coupling circuit, so that low clock input frequencies cause

electric charge to be lost.

• Use 1 MHz or more of f(XIN) during A-D conversion is performed.

• Do not execute the STP instruction during A-D conversion.

Voltages to be applied to the reference voltage input pin are as follows:

• VREF = 2 to VCC [V] when VCC = 2.7 V to 4.0 V

• VREF = 0.5 VCC to VCC [V] when VCC = 4.0 V to 5.5 V

When the A-D converter is not used, connect VREF pin to the VCC pin.

Apply the same voltage as to the VSS pin to analog power source voltage input pin AVSS. (The AVSS

pin is dedicated to the 44P6N-A package in the 7481 Group.)

Even when A-D conversion is started, the A-D conversion completion interrupt request bit is not automatically

cleared to ‘0’.

Clear this bit to ‘0’ before A-D conversion starts.

A-D conversion resumes when ‘0’ is written into the A-D conversion completion bit of the A-D control

To start A-D conversion, set the VREF connection selection bit of the A-D control register to ‘1’ to

connect ladder resistor and the VREF. A-D conversion can then be started, after the VREF stabilization

time elapses 1.0

µs or more.

1.15 A-D Converter

7480 Datasheet(PDF) 164 Page - Renesas Technology Corp