A3989SEVTR-T Allegro Microsystems Inc, A3989SEVTR-T Datasheet - Page 10

• Manufacturer Part Number: A3989SEVTR-T
• Description: IC, MOTOR DRIVER, STEPPER, 1.2A, QFN-36
• Manufacturer: Allegro Microsystems Inc

Specifications of A3989SEVTR-T

• Motor Type: Stepper
• No. Of Outputs: 3
• Output Current: 1.2A
• Output Voltage: 36V
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: QFN
• No. Of Pins: 36
• Applications: DC Motor Driver, Stepper Motor Driver
• Number Of Outputs: 2
• Voltage - Load: 8 V ~ 36 V
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 36-VFQFN Exposed Pad
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 620-1183-2

A3989
Motor Configurations
dc or dual stepper motors, Allegro offers the A3988 and A3995.
Both devices are offered in a 36 pin QFN package. Please refer to
the Allegro website for further information and datasheets for the
devices.
Layout
plane. For optimum electrical and thermal performance, the
A3989 must be soldered directly onto the board. On the under-
side of the A3989 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.
Grounding
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 exposed thermal
pad and the groundplane directly under the A3989, 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 recommended PCB layout shown
OUT1B
OUT2B
OUT2A
OUT1A
The printed circuit board should use a heavy ground-
CIN1
Figure 5. Printed circuit board layout with typical application circuit, shown at right. The copper area directly under the
A3989 (U1) is soldered to the exposed thermal pad on the underside of the device. The thermal vias serve also as electrical
vias, connecting it to the ground plane on the other side of the PCB , so the two copper areas together form the star ground.
In order to minimize the effects of ground bounce
GND
RS1
RS2
VDD
CCP
U1
For applications that require either dual
VBB
Bipolar Stepper and High Current DC Motor Driver
CVDD1
CVDD2
CVCP
GND
RS3
Applications Information
GND
CIN3
CIN2
OUT3B
OUT3A
in the diagram below, illustrates how to create a star ground
under the device, to serve both as 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 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
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.
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.
CIN1
RS1
RS2
1
The sense resistors, RSx, should have a very
NC
OUT1A
SENSE1
OUT1B
VBB
OUT2B
SENSE2
OUT2A
NC
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
CCP
A3989
PAD
CVDD1
CVDD2
V
CVCP
BB
SENSE3
SENSE3
OUT3B
OUT3B
OUT3A
OUT3A
MODE
VBB
NC
CIN3
RS3
CIN2
10