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A3987

Allegro MicroSystems
Part Number A3987
Manufacturer Allegro MicroSystems
Description DMOS Microstepping Driver
Published Apr 2, 2007
Detailed Description A3987 DMOS Microstepping Driver with Translator FEATURES AND BENEFITS ▪ Low RDS(on) outputs ▪ Short-to-ground protectio...
Datasheet PDF File A3987 PDF File

A3987
A3987

Overview
A3987 DMOS Microstepping Driver with Translator FEATURES AND BENEFITS ▪ Low RDS(on) outputs ▪ 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 PACKAGE: 24-pin TSSOP with exposed thermal pad (suffix LP) Not to scale 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 motor to take one microstep.
There are no phase sequence tables, 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.
Continued on the next page… 3987DS, Rev.
9 MCO-0000740 Typical Application Diagram Microcontroller or Controller Logic 10 µF 5 kΩ 0.
22 µF VREG VDD 0.
1 µF X7R CP1 CP2 VCP ROSC A3987 STEP DIR SLEEP/RESET ENABLE MS1 MS2 REF VBB1 VBB2 OUT1A OUT1B SENSE1 OUT2A OUT2B SENSE2 0.
1 µF X7R...


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