a4982 Allegro MicroSystems, Inc., a4982 Datasheet - Page 12

• Manufacturer Part Number: a4982
• Description: Dmos Microstepping Driver With Translator And Overcurrent Protection
• Manufacturer: Allegro MicroSystems, Inc.

A4982
Layout. Typical application circuits and layouts are shown in
figures 8 (LP package) and 9 (ET package).The printed circuit
board should use a heavy groundplane. For optimum electrical
and thermal performance, the A4982 must be soldered directly
onto the board. On the underside of the A4982 package is an
exposed pad, which provides a path for enhanced thermal dissipa-
tion. The thermal pad should be soldered directly to an exposed
surface on the PCB. Thermal vias are used to transfer heat to
other layers of the PCB.
In order to minimize the effects of ground bounce and offset
issues, it is important to have a low impedance single-point
ground, known as a star ground, located very close to the device.
By making the connection between the pad and the ground plane
directly under the A4982, that area becomes an ideal location for
a star ground point. A low impedance ground will prevent ground
bounce during high current operation and ensure that the supply
voltage remains stable at the input terminal.
ROSC
GND
GND
C5
C1
C4
VDD
GND
C3
U1
GND
GND
VBB
Figure 8. LP package typical application and circuit layout
DMOS Microstepping Driver with Translator
C6
C2
CAPACITANCE
Thermal Vias
BULK
Application Layout
PCB
R4
R5
A4982
GND
GND
GND
OUT2B
OUT1B
The two input capacitors should be placed in parallel, and as
close to the device supply pins as possible. The ceramic capaci-
tor (CIN1) should be closer to the pins than the bulk capacitor
(CIN2). This is necessary because the ceramic capacitor will be
responsible for delivering the high frequency current components.
The sense resistors, RSx , should have a very low impedance
path to ground, because they must carry a large current 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. 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.
OUT2A
OUT1A
and Overcurrent Protection
C1
Solder
Trace (2 oz.)
Signal (1 oz.)
Ground (1 oz.)
Thermal (2 oz.)
ROSC
C3
V
C5
DD
C4
CP1
CP2
VCP
VREG
MS1
MS2
RESET
ROSC
SLEEP
VDD
STEP
REF
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
A4982
PAD
ENABLE
SENSE2
SENSE1
OUT2B
OUT1B
OUT2A
OUT1A
VBB2
VBB1
GND
GND
DIR
R4
R5
V
BB
C6
C2
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