2544

QUAD DARLINGTON

POWER DRIVER

APPLICATIONS INFORMATION

A typical application is shown driving a four-phase unipolar stepper

motor. Note that with the complimentary control inputs, only two logic

signals are needed to drive the motor in the two-phase format. The two

phase drive format illustrated, energizes two adjacent phases in each

detent position (AB, BC, CD, DA) to provide an improved torque-speed

product and greater detent torque.

A Zener diode can be used to increase the flyback voltage. The

increased flyback voltage gives a much faster inductive load turn-OFF

current decay resulting in improved motor performance. The maximum

Zener voltage, plus the load supply voltage, plus the flyback diode

forward voltage must not exceed the device’s rated sustaining voltage.

With external control circuitry, the ENABLE input (active low) can be

used for chopper (PWM) applications. If the ENABLE input is not used,

it should be tied low.

All inputs will float high if open circuited.

TRUTH TABLE

INPUTS

WINDINGS

1/2

3/4

A

B

C

D

L

H

ON

ON

OFF

OFF

L

L

OFF

ON

ON

OFF

H

L

OFF

OFF

ON

ON

H

H

ON

OFF

OFF

ON

ZENER CLAMP

DIODE CLAMP

V

+ V

BB

F

V

+ V + V

BB

Z

F

TYPICAL APPLICATION

(UNIPOLAR STEPPER MOTOR WITH ZENER FLYBACK)

Dwg. EP-015

Dwg. WP-001

Allegro MicroSystems, Inc. reserves the right to make, from

time to time, such departures from the detail specifications as

may be required to permit improvements in the design of its

products.

The information included herein is believed to be accurate

and reliable. However, Allegro MicroSystems, Inc. assumes no

responsibility for its use; nor for any infringements of patents or

other rights of third parties which may result from its use.