24

23

22

21

20

19

18

17

16

15

14

13

GROUND

GROUND

SLEEP

LOAD

LOGIC

SUPPLY

MUX

REF

Dwg. PP-069-3

1

2

3

4

5

6

7

8

9

12

11

10

9

GROUND

GROUND

VCP

CP1

CP2

STROBE

CLOCK

DATA

LOAD

OSC

3973

DUAL DMOS FULL-BRIDGE MICRO-

STEPPING PWM MOTOR DRIVER

Designed for pulse-width modulated (PWM) current control of

bipolar microstepping stepper motors, the A3973SB and A3973SLB are

capable of continuous output currents to

±1 A and operating voltages to

35 V. Internal fixed off-time PWM current-control timing circuitry can

be programmed via a serial interface to operate in slow, fast, and mixed

current-decay modes. The A3973SB (DIP) and the A3973SLB (SOIC)

are electrically identical and differ only in package style.

The desired load-current level is set via the serial port with two 6-bit

linear DACs in conjunction with a reference voltage. The six bits of

control allow maximum flexibility in torque control for a variety of step

methods, from microstepping to full-step drive. Load current is set in

1.56% increments of the maximum value.

Synchronous rectification circuitry allows the load current to flow

through the low

r

decay. This feature will eliminate the need for external clamp diodes in

most applications, saving cost and external component count, while

minimizing power dissipation.

Internal circuit protection includes thermal shutdown with hyster-

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

Special power-up sequencing is not required.

The A3973SB is supplied in a 24-lead plastic DIP with a copper

batwing power tab; the A3973SLB is supplied in a 24-lead plastic SOIC

with a copper batwing power tab for surface-mount applications. The

power tabs are at ground potential and need no electrical isolation.

FEATURES

I ±1 A, 35 V Continuous Output Rating

I Optimized Microstepping via 6-Bit Linear DACs

I Programmable Mixed, Fast, and Slow Current-Decay Modes

I 4 MHz Internal Oscillator for Digital Timing

I Serial-Interface Controls Chip Functions

I Synchronous Rectification for Low Power Dissipation

I Internal UVLO and Thermal Shutdown Circuitry

I Crossover-Current Protection

I Precision 2 V Reference

I Inputs Compatible with 3.3 V or 5 V Control Signals

I Sleep and Idle Modes

PRELIMINARY INFORMATION

(Subject to change without notice)

December 1, 2000

ABSOLUTE MAXIMUM RATINGS

at T

Load Supply Voltage, V

Output Current, I

Logic Supply Voltage, V

Logic Input Voltage Range,

V

Reference Voltage, V

Sense Voltage (dc), V

Package Power Dissipation, P

D

A3973SB ............................... 3.1 W

A3973SLB ............................ 2.2 W

Operating Temperature Range,

T

Junction Temperature, T

Storage Temperature Range,

T

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 tempera-

ture of 150

°C.

Always order by complete part number, e.g., A3973SB .