ALLEGRO A3972 User Manual

A3972

Dual DMOS Full-Bridge Microstepping PWM Motor Driver

Features and Benefits

▪ ±1.5 A, 50 V Continuous Output Rating ▪ Low R ▪ Optimized Microstepping via 6-Bit Linear DACs ▪ Programmable Mixed, Fast, and Slow Current-Decay

Modes

▪ 4 MHz Internal Oscillator for Digital Timing ▪ Serial-Interface Controls Chip Functions ▪ Synchronous Rectification for Low Power Dissipation ▪ Internal UVLO and Thermal Shutdown Circuitry ▪ Crossover-Current Protection ▪ Precision 2 V Reference ▪ Inputs Compatible with 3.3 or 5 V Control Signals ▪ Sleep and Idle Modes

DMOS Output Drivers

DS(on)

Package: 24-pin DIP with 4 fused leads (suffix B)

Not to scale

Description

Designed for pulse-width modulated (PWM) current control

of bipolar microstepping stepper motors, the A3972 is capable

of continuous output currents to ±1.5 A and operating voltages

to 50 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 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

during the current 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

hysteresis, transient-suppression diodes, and crossover-current

protection. Special power-up sequencing is not required.

The A3972SB is supplied in a 24-pin plastic DIP with two

batwing power tabs (suffix ‘B’). The power tabs are at ground

potential and need no electrical isolation. The device is lead

(Pb) free with 100% matte tin leadframe plating.

of the DMOS output driver

DS(on)

29319.33, Rev. D

Pin-out Diagram

Dual DMOS Full-Bridge

A3972

Microstepping PWM Motor Driver

Selection Guide

Part Number Packing

A3972SB-T 15 pieces/tube

Absolute Maximum Ratings

Characteristic Symbol Notes Rating Units

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

Operating Ambient Temperature T

Junction Temperature T

Storage Temperature T

*Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the speciﬁ ed current rating or a junction temperature of 150°C.

OUT

REF

stg

Range S –20 to 85 ºC

50 V

±1.5 A

7.0 V

–0.3 to VDD + 0.3 V

500 mV

3.1 W

150 ºC

–55 to 150 ºC

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

A3972

Dual DMOS Full-Bridge

Microstepping PWM Motor Driver

FUNCTIONAL BLOCK DIAGRAM

LOGIC

SUPPLY

CLOCK

DATA

STROBE

SLEEP

MUX

OSC

OSCILATOR

OSC SELECT/

DIVIDER

SERIAL

PORT

2 V

UVLO AND

FAULT

DETECT

6-BIT LINEAR DAC

2 V

REGULATOR

BANDGAP

PROGRAMMABLE

PWM TIMER

FIXED-OFF BLANK MIXED DECAY

CONTROL

LOGIC

PHASE 1/2 SYNC. RECT. MODE SYNC. RECT. DISABLE MODE 1/2

PROGRAMMABLE

PWM TIMER

FIXED-OFF BLANK MIXED DECAY

SENSE

GATE

DRIVE

0.22 μF

REG

0.22 μF

CP1CP2

CHARGE PUMP

DMOS H-BRIDGE

OUT

BB1

OUT

SENSE

BB2

OUT

0.1 μF

0.22 μF

LOAD

SUPPLY

REF

Dwg. FP-050-1

BUFFER

6-BIT LINEAR DAC

GROUND

SENSE

Allegro MicroSystems, Inc. 115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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