A3955 查看數據表（PDF） - Allegro MicroSystems

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A3955

Full-Bridge PWM Microstepping Motor Driver

Allegro MicroSystems 

A3955

Full-Bridge PWM Microstepping Motor Driver

Features and Benefits

▪ ±1.5 A continuous output current

▪ 50 V output voltage rating

▪ Internal PWM current control

▪ 3-bit nonlinear DAC

▪ Fast, mixed fast/slow, and slow current-decay modes

▪ Internal transient-suppression diodes

▪ Internal thermal shutdown circuitry

▪ Crossover-current and UVLO protection

Packages:

Package B, 16-pin DIP

with exposed tabs

Package LB, 16-pin SOIC

with internally fused pins

Not to scale

Description

The A3955 is designed to drive one winding of a bipolar

stepper motor in a microstepping mode. The outputs are

rated for continuous output currents to ±1.5 A and operating

voltages to 50 V. Internal pulse width modulated (PWM) current

control combined with an internal three-bit nonlinear digital-

to-analog converter allows the motor current to be controlled

in full-, half-, quarter-, or eighth-step (microstepping) modes.

Nonlinear increments minimize the number of control lines

necessary for microstepping. Microstepping provides increased

step resolution, and reduces torque variations and resonance

problems at low speed.

Internal circuitry determines whether the PWM current-control

circuitry operates in a slow (recirculating) current-decay

mode, fast (regenerative) current-decay mode, or in a mixed

current-decay mode in which the off-time is divided into a

period of fast current decay and with the remainder of the

fixed off-time spent in slow current decay. The combination of

user-selectable current-sensing resistor and reference voltage,

digitally selected output current ratio; and slow, fast, or mixed

current-decay modes provides users with a broad, variable

range of motor control.

Continued on the next page…

Functional Block Diagram

29319.41E

PHASE

7

GROUND

4

5

12

13

UVLO

& TSD

6

10

15

16

VCC

VBB

PFD 1

MIXED-DECAY

COMPARATOR

+

–

BLANKING

VCC

PWM LATCH

R

Q

S

BLANKING

GATE

CURRENT-SENSE

COMPARATOR

+

–

÷3

D/A

+–

RC

3

VTH 2

8 9 14

SENSE

11

DISABLE

RS

CT

RT

Dwg. FP-042

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