A3987
DMOS Microstepping Driver with Translator
Features and Benefits
Description
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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.
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)
Approximate scale
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…
Typical Application Diagram
0.1 μF
X7R
0.22 μF
VREG
CP1
VCP
VDD
10 μF
CP2
0.1 μF
X7R
5 kΩ
Microcontroller or
Controller Logic
ROSC
VBB1
A3987
STEP
DIR
SLEEP/RESET
VBB2
OUT1A
OUT1B
SENSE1
ENABLE
MS1
MS2
REF
OUT2A
OUT2B
SENSE2
3987DS, Rev. 6
100 μF
