A3983SLPTR-T(2009) Ver la hoja de datos (PDF) - Allegro MicroSystems
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A3983SLPTR-T Datasheet PDF : 12 Pages
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A3983
DMOS Microstepping Driver with Translator
Application Layout
Layout. The printed circuit board should use a heavy ground-
plane. For optimum electrical and thermal performance, the
A3983 must be soldered directly onto the board. On the under-
side of the A3983 package is an exposed pad, which provides a
path for enhanced thermal dissipation. 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 A3983, 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. The star ground can
be created using the exposed thermal pad under the device, to
serve both as a low impedance ground point and thermal path.
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.
A3983
PCB
Thermal Vias
Solder
Trace (2 oz.)
Signal (1 oz.)
Ground (1 oz.)
Thermal (2 oz.)
C3
C4
GND
C5
ROSC
C1
GND
GND
VDD
C6
GND
U1
OUT2B
GND
OUT2A
R4
R5
OUT1A
GND
GND
VBB
BULK
OUT1B
CAPACITANCE
C2
GND
C3
C4
C5
ROSC
C1
VDD
CP1
A3983
GND
CP2
VCP
ENABLE
OUT2B
VBB2
VREG
MS1
MS2
RESET
ROSC
SLEEP
VDD
STEP
PAD SENSE2
OUT2A R4
OUT1A
SENSE1
R5
VBB1
OUT1B
DIR
REF
GND
C6
C2
VBB
Allegro MicroSystems, Inc.
7
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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