Description

The A3987 is a complete microstepping motor driver with

built-in translator for easy operation. It is designed to operate

bipolar stepper motors in full, half, quarter, and sixteenth step

modes, with output drive capability of 50 V and

±1.5 A. The

A3987 includes a fixed off-time current regulator, which has

the ability to operate in slow or mixed decay modes.

The translator is the key to the easy implementation of the

A3987. Simply inputting one pulse on the step input drives the

motortotakeonemicrostep.Therearenophasesequencetables,

high frequency control lines, or complex interfaces to program.

The A3987 interface is an ideal fit for applications where a

complex microprocessor is unavailable or over-burdened.

The A3987 chopping control automatically selects the current

decay mode (slow or mixed). When a STEP signal occurs,

the translator determines if that step results in a higher or

lower current in each of the motor phases. If the change is to

a higher current, then the decay mode is set to slow decay. If

the change is to a lower current, then the decay mode is set to

30.1% fast decay. This current decay control scheme results

in reduced audible motor noise, increased step accuracy, and

reduced power dissipation.

3987DS, Rev.1

Features and Benefits

▪ Short-to-ground protection

▪ Shorted load protection

▪ Automatic current decay mode detection/selection

▪ Mixed and slow current decay modes

▪ Synchronous rectification for low power dissipation

▪ Internal UVLO and thermal shutdown circuitry

▪ Crossover-current protection

DMOS Microstepping Driver with Translator

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Package: 24 pin TSSOP with exposed

thermal pad (suffix LP)

Typical Application Diagram

Approximate scale

Microcontroller or

Controller Logic

ROSC

VDD

VREG

CP1

CP2

VCP

VBB1

VBB2

OUT1A

OUT1B

SENSE1

SENSE2

OUT2A

OUT2B

A3987

0.22 μF

0.1 μF

X7R

100 μF

0.1 μF

X7R

10 μF

5 kΩ

STEP

DIR

ENABLE

MS1

MS2

REF

SLEEP/RESET

A3987