The A3957SA and A3957SLB are designed for driving one winding of a

bipolar stepper motor in a microstepping mode. The outputs are rated for

continuous output currents to

±1.5 A and operating voltages to 50 V. Internal

pulse-width modulated (PWM) current control combined with an internal

four-bit nonlinear digital-to-analog converter allows the motor current to be

controlled in full-, half-, quarter-, eighth-, or sixteenth-step (microstepping)

modes. Nonlinear increments minimize the number of control lines necessary

for microstepping. Microstepping provides for increased step resolution, and

reduces torque variations and resonance problems at low speed.

Internal circuitry determines whether the PWM current-control circuitry

operates in a slow (recirculating) current-decay mode, fast (regenerative)

current-decay mode, or in a mixed current-decay mode in which the off time

is divided into a period of fast current decay with the remainder of the fixed

off time spent in slow current decay. The combination of user-selectable

current-sensing resistor and reference voltage, digitally selected output

current ratio; and slow, fast, or mixed current-decay modes provides users

with a broad, variable range of motor control.

Internal circuit protection includes thermal shutdown with hysteresis,

transient-suppression diodes, and crossover current protection. Special

power-up sequencing is not required.

The A3957S— is supplied in a choice of two power packages; a 16-pin

dual-in-line plastic package (suffix ‘A’), and a 24-lead plastic SOIC with

copper heat-sink tabs (suffix ‘LB’). The power tab is at ground potential and

needs no electrical isolation.

FEATURES

s

±1.5 A Continuous Output Current

s 50 V Output Voltage Rating

s Internal PWM Current Control

s 4-Bit Non-Linear DAC for 16-Bit Microstepping

s Satlington™ Sink Drivers

s Fast, Mixed Fast/Slow, and Slow Current-Decay Modes

s Internal Transient-Suppression Diodes

s Internal Thermal-Shutdown Circuitry

s Crossover-Current and UVLO Protection

FULL-BRIDGE PWM

MICROSTEPPING MOTOR DRIVER

3957

Always order by complete part number:

Part Number

Package

A3957SA

16-pin DIP

60

°C/W

38

°C/W

—

A3957SLB

24-lead batwing SOIC

56

°C/W

—

6

°C/W

ABSOLUTE MAXIMUM RATINGS

(Continuous) . . . . . . . . . . . . .

7.0 V

Logic/Reference Input Voltage Range,

1.0 V

A3957SA . . . . . . . . . . . . . . . . 2.08 W†

A3957SLB . . . . . . . . . . . . . . . 2.23 W†

Operating Temperature Range,

Storage Temperature Range,

* Output current rating may be limited by duty

cycle, ambient temperature, and heat sinking.

Under any set of conditions, do not exceed the

specified current rating or a junction temperature

of 150

°C.

† Per SEMI G42-88 Specification, Thermal Test

Board Standardization for Measuring Junction-

to-Ambient Thermal Resistance of Semiconductor

Packages..

GROUND

GROUND

LOGIC

SUPPLY

PHASE

GROUND

GROUND

RC

SENSE

D

Dwg. PP-056-4

REF

LOAD

SUPPLY

OUTB

OUTA

LOGIC

PFD

1

D 0

D 2

1

2

3

22

23

24

6

7

18

19

4

5

21

20

8

9

10

15

16

17

11

12

14

13

NO

CONNECT

NO

CONNECT

NO

CONNECT

D 3

NO

CONNECT

NO

CONNECT

NO

CONNECT

NO

CONNECT

NC

NC

NC

NC

NC

NC

NC

A3957SLB