AGND

connected together externally

Description

The A3979 is a complete microstepping motor driver with

built-in translator, designed as a pin-compatible replacement for

precision. It is designed to operate bipolar stepper motors in

full-, half-, quarter-, and sixteenth-step modes, with an output

drive capacity of up to 35 V and ±2.5 A. The A3979 includes a

fixed off-time current regulator that has the ability to operate in

Slow, Fast, or Mixed decay modes. This current-decay control

scheme results in reduced audible motor noise, increased step

accuracy, and reduced power dissipation.

The translator is the key to the easy implementation of the

A3979. It allows the simple input of one pulse on the STEP

pin to drive the motor one microstep, which can be either a full

step, half, quarter, or sixteenth, depending on the setting of the

MS1 and MS2 logic inputs.There are no phase-sequence tables,

high-frequency control lines, or complex interfaces to program.

The A3979 interface is an ideal fit for applications where a

complex microprocessor is unavailable or is overburdened.

Internal synchronous-rectification control circuitry is provided

to improve power dissipation during PWM operation. Internal

circuit protection includes: thermal shutdown with hysteresis,

UVLO (undervoltage lockout), and crossover-current

protection. Special power-on sequencing is not required.

26184.23C

Features and Benefits

▪ ±2.5 A, 35 V output rating

▪ Automatic current decay mode detection/selection

▪ 3.0 to 5.5 V logic supply voltage range

▪ Slow, Fast or Mixed current decay modes

▪ Home output

▪ Synchronous rectification for low power dissipation

▪ Internal UVLO and thermal shutdown circuitry

▪ Crossover-current protection

Microstepping DMOS Driver with Translator

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Package: 28 lead TSSOP (suffix LP) with

exposed thermal pad

Device Diagram

A3979

7

8

9

10

11

12

13

6

5

20

19

18

17

16

15

21

22

14

1

2

3

4

26

25

28

27

24

23

VCP

PGND

VREG

STEP

OUT2B

RESET

SR

VBB2

PFD

RC1

AGND

REF

RC2

VDD

OUT2A

MS2

MS1

SENSE2

SENSE1

HOME

DIR

OUT1A

ENABLE

OUT1B

CP2

CP1

SLEEP

VBB1

Translator

and

Control

Logic

÷8

Reg

Charge

Pump

PWM

Timer