M63154AFP

Rev.1.0, Sep.16.2003, page 10 of 15

PWM Function Description

Chopping PWM control is applied to supply driving current to the motor in proportion to the analog-voltage input.

This IC detects the flow of current to the motor and the power supply continues to supply current until it reaches a level

specified in terms of the input voltage (current path 1). At that time, the output transistors are switched, and energy

stored in the coil regenerates current for a period determined by the internal off-timer circuit (current path 2). When the

timer reaches the specified value, the power supply again starts to supply current. Operation proceeds through repetition

of these phases.

[ FORWARD Current path timing 2.]

Current path 2

Vcc

RS

GND

OUTPUT-A

OUTPUT-B

[ FORWARD Current path timing 1.]

Current path1

Vcc

RS

OUTPUT- A

GND

OUTPUT-B

Time

Off time

Motor current

Control value

Control value

(Vcc-VRS)

Io=

Current

path 1

Current

path 2