DMOS Microstepping Driver with Translator and Overcurrent ...

[Pages:20]A4988

DMOS Microstepping Driver with Translator and Overcurrent Protection

Features and Benefits

Low Rds(on) outputs Automatic current decay mode detection/selection Mixed and slow current decay modes Synchronous rectification for low power dissipation Internal UVLO Crossover-current protection 3.3 and 5 V compatible logic supply Thermal shutdown circuitry Short-to-ground protection Shorted load protection Five selectable step modes: full, 1/2, 1/4, 1/8, and 1/16

Package:

28-contact QFN with exposed thermal pad

5 mm ? 5 mm ? 0.90 mm (ET package)

Not to scale

Description

The A4988 is a complete microstepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors in full-, half-, quarter-, eighth-, and sixteenth-step modes, with an output drive capacity of up to 35 V and ?2 A. The A4988 includes a fixed off-time current regulator which has the ability to operate in slow or mixed decay modes.

The translator is the key to the easy implementation of the A4988. Simply inputting one pulse on the STEP input drives the motor one microstep. There are no phase sequence tables, high-frequency control lines, or complex interfaces to program. The A4988 interface is an ideal fit for applications where a complex microprocessor is unavailable or is overburdened.

During stepping operation, the chopping control in the A4988 automatically selects the current decay mode: slow or mixed. In mixed decay mode, the device is set initially to a fast decay for a proportion of the fixed off-time, then to a slow decay for the remainder of the off-time. Mixed decay current control results in reduced audible motor noise, increased step accuracy, and reduced power dissipation.

Continued on the next page...

Microcontroller or Controller Logic

Typical Application Diagram

VDD 0.22 ?F

0.1 ?F

0.1 ?F

0.22 ?F

5 k

VREG ROSC CP1 VDD

CP2

VCP VBB1 VBB2

SLEEP

STEP MS1 MS2 MS3 DIR ENABLE RESET VREF

A4988

OUT1A

OUT1B SENSE1

GND

OUT2A OUT2B SENSE2 GND

4988-DS, Rev. 6

100 ?F

A4988

DMOS Microstepping Driver with Translator and Overcurrent Protection

Description (continued)

Internal synchronous rectification control circuitry is provided to improve power dissipation during PWM operation. Internal circuit protection includes: thermal shutdown with hysteresis, undervoltage lockout (UVLO), and crossover-current protection. Special power-on sequencing is not required.

TheA4988 is supplied in a surface-mount QFN package (ET), 5 mm ? 5 mm, with a nominal overall package height of 0.90 mm and an exposed pad for enhanced thermal dissipation. It is lead (Pb) free (suffix?T), with 100% matte-tin-plated leadframes.

Selection Guide

Part Number

Package

A4988SETTR-T

28-contact QFN with exposed thermal pad

Packing 1500 pieces per 7-in. reel

Absolute Maximum Ratings

Characteristic Load Supply Voltage Output Current Logic Input Voltage Logic Supply Voltage Motor Outputs Voltage Sense Voltage Reference Voltage Operating Ambient Temperature Maximum Junction Storage Temperature

Symbol VBB IOUT VIN VDD

VSENSE VREF TA

TJ(max) Tstg

Range S

Notes

Rating 35 ?2

?0.3 to 5.5 ?0.3 to 5.5 ?2.0 to 37 ?0.5 to 0.5

5.5 ?20 to 85

150 ?55 to 150

Units V A V V V V V ?C ?C ?C

Allegro MicroSystems, LLC

2

115 Northeast Cutoff

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

1.508.853.5000;

A4988

DMOS Microstepping Driver with Translator and Overcurrent Protection

Functional Block Diagram

VREG

0.22 ?F

ROSC

0.1 ?F

CP1

CP2

VDD

Current Regulator

OSC

Charge Pump

VCP

REF

DAC

STEP DIR

RESET MS1 MS2 MS3

ENABLE SLEEP

Translator DAC

PWM Latch Blanking

Mixed Decay

Control Logic

PWM Latch Blanking

Mixed Decay

DMOS Full Bridge

OCP

Gate Drive

DMOS Full Bridge

OCP

VBB1 OUT1A OUT1B SENSE1 VBB2 OUT2A OUT2B SENSE2

VREF

0.1 ?F RS1 RS2

Allegro MicroSystems, LLC

3

115 Northeast Cutoff

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

1.508.853.5000;

A4988

DMOS Microstepping Driver with Translator and Overcurrent Protection

ELECTRICAL CHARACTERISTICS1 at TA = 25?C, VBB = 35 V (unless otherwise noted)

Characteristics

Symbol

Test Conditions

Output Drivers

Load Supply Voltage Range

VBB

Operating During Sleep Mode

Logic Supply Voltage Range Output On-Resistance Body Diode Forward Voltage

Motor Supply Current

VDD Rds(on)

VF

IBB

Operating

Source driver, IOUT = ?1.5 A Sink driver, IOUT = 1.5 A Source diode, IF = ?1.5 A Sink diode, IF = 1.5 A fPWM < 50 kHz Operating, outputs disabled

Sleep Mode

Min.

8 0 3 ? ? ? ? ? ? ?

Typ.2

? ? ? 320 320 ? ? ? ? ?

Max.

35 35 5.5 430 430 1.2 1.2 4 2 10

Units

V V V m m V V mA mA ?A

Logic Supply Current

Control Logic Logic Input Voltage

Logic Input Current

Microstep Select

Logic Input Hysteresis Blank Time Fixed Off-Time Reference Input Voltage Range Reference Input Current

Current Trip-Level Error3

Crossover Dead Time Protection Overcurrent Protection Threshold4 Thermal Shutdown Temperature Thermal Shutdown Hysteresis VDD Undervoltage Lockout VDD Undervoltage Hysteresis

IDD

VIN(1) VIN(0) IIN(1) IIN(0) RMS1 RMS2 RMS3 VHYS(IN) tBLANK

tOFF VREF IREF

errI

tDT

IOCPST TTSD TTSDHYS VDDUVLO VDDUVLOHYS

fPWM < 50 kHz Outputs off Sleep Mode

VIN = VDD ? 0.7 VIN = VDD ? 0.3 MS1 pin MS2 pin MS3 pin As a % of VDD OSC = VDD or GND ROSC = 25 k

VREF = 2 V, %ITripMAX = 38.27% VREF = 2 V, %ITripMAX = 70.71% VREF = 2 V, %ITripMAX = 100.00%

VDD rising

?

?

8

mA

?

?

5

mA

?

?

10

?A

VDD ? 0.7

?

?

V

?

? VDD ? 0.3 V

?20

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download