A3988_11 Datasheet, PDF (10/14 Pages) Allegro MicroSystems – The A3988 is a quad DMOS full-bridge driver capable of driving up to two stepper motors or four DC motors.

A3988
Quad DMOS Full Bridge PWM Motor Driver
The two input capacitors should be placed in parallel, and as
close to the device supply pins as possible. The ceramic capaci-
tor should be closer to the pins than the bulk capacitor. This is
necessary because the ceramic capacitor will be responsible for
delivering the high frequency current components.
Sense Pins The sense resistors, RSx, should have a very low
impedance path to ground, because they must carry a large cur-
rent while supporting very accurate voltage measurements by
the current sense comparators. Long ground traces will cause
additional voltage drops, adversely affecting the ability of the
comparators to accurately measure the current in the windings.
As shown in the layout below, the SENSEx pins have very short
traces to the RSx resistors and very thick, low impedance traces
directly to the star ground underneath the device. If possible,
there should be no other components on the sense circuits.
Note: When selecting a value for the sense resistors, be sure not to
exceed the maximum voltage on the SENSEx pins of ±500 mV.
Allegro MicroSystems, Inc.
10
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com