Note the A3955SB (DIP) and the A3955SLB

(SOIC) are electrically identical and share a

common terminal number assignment.

ABSOLUTE MAXIMUM RATINGS

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

Logic/Reference Input Voltage Range,

Package Power Dissipation,

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.

† Fault conditions that produce excessive junction

temperature will activate the device’s thermal

shutdown circuitry. These conditions can be

tolerated but should be avoided.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

GROUND

GROUND

LOGIC

SUPPLY

PHASE

GROUND

GROUND

RC

SENSE

D

Dwg. PP-056-2

REF

LOAD

SUPPLY

OUTB

OUTA

LOGIC

PFD

1

D 0

D 2

The A3955SB and A3955SLB 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 com-

bined with an internal three-bit nonlinear digital-to-analog converter

allows the motor current to be controlled in full-, half-, quarter-, or

eighth-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 hyster-

esis, transient-suppression diodes, and crossover current protection.

Special power-up sequencing is not required.

The A3955S— is supplied in a choice of two power packages; a

16-pin dual-in-line plastic package with copper heat-sink tabs (suffix

‘B’), and a 16-lead plastic SOIC with copper heat-sink tabs (suffix ‘LB’).

For both package styles, 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 3-Bit Non-Linear DAC

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

Part Number

Package

A3955SB

16-Pin DIP

A3955SLB

16-Lead SOIC

Always order by complete part number:

3955