Data Sheet

ManualsBrandsPololu ManualsStepper Motor ControllersA4988 Stepper Motor Driver Carrier with Voltage Regulators

Features and Benefits

 Low R

DS(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,

, and

Package:

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.

DMOS Microstepping Driver with Translator

and Overcurrent Protection

Continued on the next page…

A4988

Microcontroller or

Controller Logic

VREF

GND GND

RESET

ENABLE

SLEEP

DIR

MS2

MS3

MS1

STEP

VBB1

CP1 VCPVREG

VDD

ROSC

5 k

0.22 F

0.1 F0.1 F

100 F

CP2

VBB2

OUT1A

OUT1B

SENSE1

OUT2A

OUT2B

SENSE2

A4988

Approximate size

28-contact QFN

with exposed thermal pad

5 mm × 5 mm × 0.90 mm

(ET package)

Typical Application Diagram

4988-DS, Rev. 1

Summary of content (19 pages)

PAGE 1
A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection Features and Benefits 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.
PAGE 2
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 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.
PAGE 3
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 Functional Block Diagram 0.1 MF 0.22 MF VREG VDD Current Regulator ROSC CP1 CP2 Charge Pump OSC VCP 0.1 MF DMOS Full Bridge REF DAC VBB1 OUT1A OUT1B PWM Latch Blanking Mixed Decay STEP OCP SENSE1 Gate Drive DIR RESET MS1 Translator Control Logic MS2 PWM Latch Blanking Mixed Decay ENABLE SLEEP DAC VBB2 RS1 OUT2A OCP MS3 DMOS Full Bridge OUT2B SENSE2 RS2 VREF Allegro MicroSystems, Inc.
PAGE 4
A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection ELECTRICAL CHARACTERISTICS1 at TA = 25°C, VBB = 35 V (unless otherwise noted) Characteristics Output Drivers Load Supply Voltage Range Logic Supply Voltage Range Output On Resistance Min. Typ.2 Max. Units 8 3.0 – – – – – – – – – – 320 320 – – – – – – 35 5.5 430 430 1.2 1.2 4 2 8 5 V V mΩ mΩ V V mA mA mA mA VIN(1) VDD0.7 – – V VIN(0) – – V –20 <1.0 VDD0.3 20 –20 <1.0 20 μA – – – 5 0.
PAGE 5
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 THERMAL CHARACTERISTICS Characteristic Symbol Package Thermal Resistance RθJA Test Conditions* Value Units Four-layer PCB, based on JEDEC standard 32 ºC/W *Additional thermal information available on Allegro Web site. Power Dissipation versus Ambient Temperature 4.00 Power Dissipation, PD (W) 3.50 3.00 2.50 R QJ 2.00 A = 32 ºC /W 1.50 1.00 0.
PAGE 6
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 tA tB STEP tC tD MS1, MS2, MS3, RESET, or DIR Time Duration Symbol Typ. Unit STEP minimum, HIGH pulse width tA 1 μs STEP minimum, LOW pulse width tB 1 μs Setup time, input change to STEP tC 200 ns Hold time, input change to STEP tD 200 ns Figure 1. Logic Interface Timing Diagram Table 1.
PAGE 7
A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection Functional Description Device Operation. The A4988 is a complete microstepping motor driver with a built-in translator for easy operation with minimal control lines. It is designed to operate bipolar stepper motors in full-, half-, quarter-, eighth, and sixteenth-step modes.
PAGE 8
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 Slow Decay Mixed Decay Slow Decay Mixed Decay Slow Decay Mixed Decay Slow Decay Mixed Decay Missed Step Voltage on ROSC terminal 2 V/div. Step input 10 V/div. t → , 1 s/div. Figure 2. Missed steps in low-speed microstepping Mixed Decay ILOAD 500 mA/div. Step input 10 V/div. No Missed Steps t → , 1 s/div. Figure 3.
PAGE 9
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 tion of current flow in each winding. The size of the increment is determined by the combined state of the MSx inputs. Direction Input (DIR). This determines the direction of rotation of the motor. Changes to this input do not take effect until the next STEP rising edge. Internal PWM Current Control.
PAGE 10
A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection VREG (VREG). This internally-generated voltage is used to operate the sink-side FET outputs. The VREG pin must be decoupled with a 0.22 μF ceramic capacitor to ground. VREG is internally monitored. In the case of a fault condition, the FET outputs of the A4988 are disabled. 5 A / div.
PAGE 11
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 VSTEP 100.00 70.71 See Enlargement A IOUT 0 –70.71 –100.00 Enlargement A toff IPEAK tFD tSD Slow Decay Mixed Decay IOUT Fa st De ca y t Symbol toff IPEAK Characteristic Device fixed off-time Maximum output current tSD Slow decay interval tFD Fast decay interval IOUT Device output current Figure 7. Current Decay Modes Timing Chart Allegro MicroSystems, Inc.
PAGE 12
A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection Application Layout Solder A4988 Trace (2 oz.) Signal (1 oz.) Ground (1 oz.) PCB Thermal (2 oz.
PAGE 13
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 Pin Circuit Diagrams VDD VBB VBB 8V GND GND SENSE GND CP2 GND GND GND GND GND VBB 10 V CP1 40 V PGND VREG VCP VREG DMOS Parasitic GND 8V MS1 MS2 MS3 DIR VREF ROSC SLEEP VBB OUT DMOS Parasitic 8V GND DMOS Parasitic GND GND Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.
PAGE 14
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 STEP STEP 100.00 100.00 70.71 70.71 Mixed* Slow –70.71 –100.00 100.00 Home Microstep Position 0.00 Phase 2 IOUT2A Direction = H (%) –100.00 100.00 70.71 Phase 2 IOUT2B Direction = H (%) 0.00 Slow Slow Mixed Mixed 0.00 –70.71 70.
PAGE 15
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 STEP 100.00 92.39 83.15 70.71 55.56 Mixed* 38.27 19.51 Slow –19.51 –38.27 –55.56 –70.71 –83.15 –92.39 –100.00 100.00 92.39 83.15 70.71 55.56 Phase 2 IOUT2B Direction = H (%) Mixed Slow Mixed Mixed Slow 0.00 Home Microstep Position Phase 1 IOUT1A Direction = H (%) Mixed* 38.27 19.51 0.00 Mixed Slow –19.51 –38.27 –55.56 –70.71 –83.15 –92.39 –100.00 *With ROSC pin tied to GND DIR= H Figure 11.
PAGE 16
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 STEP 100.00 95.69 88.19 83.15 77.30 70.71 63.44 55.56 47.14 Mixed* 38.27 29.03 19.51 Phase 1 IOUT1A Direction = H (%) 9.8 Slow 0.00 Mixed Slow Mixed –9.8 –19.51 –29.03 Home Microstep Position –38.27 –47.14 –55.56 –63.44 –70.71 –77.30 –83.15 –88.19 –95.69 –100.00 100.00 95.69 88.19 83.15 77.30 70.71 63.44 55.56 47.14 Mixed* 38.27 29.03 19.51 Phase 2 IOUT2B Direction = H (%) 9.8 0.00 Slow Mixed Slow Mixed Slow –9.
PAGE 17
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 Table 2. Step Sequencing Settings Home microstep position at Step Angle 45º; DIR = H Full Step # Half Step # 1 1/4 Step # 1 2 2 3 5 6 4 7 8 (%) 100.00 (%) 0.00 2 99.52 9.80 5.6 98.08 19.51 11.3 4 95.69 29.03 16.9 5 92.39 38.27 22.5 6 88.19 47.14 28.1 7 83.15 55.56 33.8 8 77.30 63.44 39.4 9 70.71 70.71 45.0 3 5 10 63.44 77.30 50.6 11 55.56 83.15 56.3 12 47.14 88.19 61.
PAGE 18
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 22 VBB1 23 SENSE1 24 OUT1A 25 NC 26 OUT2A 27 SENSE2 28 VBB2 Pin-out Diagram OUT2B 1 21 OUT1B ENABLE 2 20 NC GND 3 CP1 4 CP2 5 17 REF VCP 6 16 STEP NC 7 15 VDD SLEEP 14 ROSC 13 18 GND RESET 12 MS3 11 9 MS1 MS2 10 8 VREG Terminal List Table 19 DIR PAD Name Number Description CP1 4 Charge pump capacitor terminal CP2 5 Charge pump capacitor terminal VCP 6 Reservoir capacitor terminal VREG
PAGE 19
DMOS Microstepping Driver with Translator and Overcurrent Protection A4988 ET Package, 28-Pin QFN with Exposed Thermal Pad 0.30 5.00 ±0.15 1.15 28 1 2 0.50 28 1 A 5.00 ±0.15 3.15 4.80 3.15 29X D SEATING PLANE 0.08 C C 4.80 C +0.05 0.25 –0.07 PCB Layout Reference View 0.90 ±0.10 0.50 For Reference Only; not for tooling use (reference JEDEC MO-220VHHD-1) Dimensions in millimeters Exact case and lead configuration at supplier discretion within limits shown 0.