A3988 查看數據表（PDF） - Allegro MicroSystems

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A3988

Quad DMOS Full Bridge PWM Motor Driver

Allegro MicroSystems 

A3988

Quad DMOS Full Bridge PWM Motor Driver

Applications Information

Motor Configurations For applications that require either a

stepper/dc motor driver or dual dc motor driver, Allegro offers the

A3989 and A3995. These devices are offered in the same 36 pin

QFN package as the A3988. The dc motor drivers are capable of

supplying 2.4 A at 36 V. Commutation is done with a standard

phase/enable logic interface. Please refer to the Allegro website

for further information and datasheets about those devices.

DC Motor Control Each of the 4 full bridges has independent

PWM current control circuitry that makes the A3988 capable of

driving up to four dc motors at currents up to 1.2 A. Control of

the dc motors is accomplished by tying the I0, I1 pins together

creating an equivalent ENABLE function with maximum current

defined by the voltage on the corresponding VREF pin. The dc

motors can be driven via a PWM signal on this enable signal, or

on the corresponding PHASE pin. Motor control includes for-

ward, reverse, and coast.

Layout The printed circuit board should use a heavy ground-

plane. For optimum electrical and thermal performance, the

A3988 must be soldered directly onto the board. On the under-

side of the A3988 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 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 exposed thermal

pad and the groundplane directly under the A3988, 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

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.

A3988

PCB

Thermal Vias

Solder

Trace (2 oz.)

Signal (1 oz.)

Ground (1 oz.)

Thermal (2 oz.)

OUT1A

OUT1B

OUT2B

OUT2A

GND

CCP

RS1

U1

VBB

CVCP

GND

CIN3

RS3

CIN1

RS2

VDD

CIN2

RS4

CVDD1

CVDD2

GND

OUT3A

OUT3B

OUT4B

OUT4A

RS1

CIN1

RS2

1

I04

OUT1A

SENSE1

OUT1B

VBB1

OUT2B

SENSE2

OUT2A

PHASE4

EV package layout shown

VBB

CVCP

CIN3

CCP

A3988

PAD

I13

OUT3A

SENSE3

OUT3B

VBB2

OUT4B

SENSE4

OUT4A

I14

RS3

CIN2

RS4

CVDD1

CVDD2

Figure 6. Printed circuit board layout with typical application circuit, shown at right. The copper area directly under the

A3988 (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.

Allegro MicroSystems, Inc.

9

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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