ALLEGRO A3979 User Manual

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Microstepping DMOS Driver with Translator

Package LP, 28-pin TSSOP with Exposed Thermal Pad

SENSE1

HOME

DIR

OUT1A

PFD

RC1

AGND

REF

RC2

VDD

OUT2A

MS2

MS1

SENSE2

PWM Timer

AGND and PGND must be

connected together externally.

÷8

Translator

and

Control

Logic

Approximate Scale 1:1

AB SO LUTE MAX I MUM RAT INGS

Load Supply Voltage,V Output Current, I

OUT

Logic Supply Voltage, V Logic Input Voltage Range, V t

> 30 ns........................–0.3 V to VDD + 0.3 V

< 30 ns..............................–1 V to VDD + 1 V

Sense Voltage, V

SENSE

Reference Voltage, V Package Power Dissipation, P Operating Temperature Range Ambient, T

, Range S ...................–20°C to 85°C

Junction Temperature, T Storage Temperature, T

Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the specified current rating or a junction temperature of 150°C.

...................................35 V

...................................... ±2.5 A

...............................7.0 V

.......................................0.5 V

......................................V

REF

.................See page 5

J(MAX)

.................... –55°C to 150°C

VBB1

SLEEP

ENABLE

OUT1B

CP2

CP1

VCP

PGND

VREG

STEP

OUT2B

RESET

VBB2

Charge

Pump

Reg

.....................150°C

A3979

The A3979 is a complete microstepping motor driver with built-in translator, designed as a pin-compatible replacement for the successful A3977, with enhanced microstepping (1/16 step) precision. It is designed to operate bipolar stepper motors in full-, half-, quarter-, and sixteenthstep 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.

The A3979 is supplied in a low-profile (maximum height ≤ 1.20 mm), 28-pin TSSOP with exposed thermal pad. The package is available in a lead (Pb) free version, with 100% matte tin leadframe plating.

FEATURES

 ±2.5 A, 35 V output rating  Low R  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

Use the following complete part number when ordering:

Part Number Pb-free Ambient, TA (°C)

A3979SLP – A3979SLP-T Yes

outputs: 0.28 Ω source, 0.22 Ω sink, typical

DS(On)

–20 to 85

26184.23

DMOS Microstepping Driver with Translator

Functional Block Diagram

A3979

Logic Supply

Reference Supply

STEP

RESET

HOME

SLEEP

ENABLE

PFD

0.1 µF

VDD

REF

RC1

DIR

MS1

MS2

PFD

RC2

UVLO and

Fault

Translator

Charge

Pump

0.22 µF

CP1

VCP

VBB1

OUT1A

OUT1B

SENSE1

VBB2

OUT2A

OUT2B

SENSE2

0.22 µF

>47 µF

Load

Supply

0.22 µF

VREG

Regulator

Bandgap

DAC

PWM Timer:

PWM Latch

Blanking

Mixed Decay

Gate Drive

Control

Logic

PWM Timer:

PWM Latch

Blanking

Mixed Decay

CP2

2 V

DMOS Full Bridge

26184.23

AGND PGND

DAC

Exposed Thermal Pad

(Required)

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

A3979

DMOS Microstepping Driver with Translator

ELECTRICAL CHARACTERISTICS at T

Characteristics Symbol Test Conditions Min.

Output Drivers

Load Supply Voltage Range V

Output Leakage Current

Output On Resistance R

Body Diode Forward Voltage V

Motor Supply Current I

Control Logic

Logic Supply Voltage Range V

Logic Supply Current I

Logic Input Voltage

Logic Input Current

Reference Input Voltage Range V Reference Input Current I

HOME Output Voltage

Mixed Decay Mode Trip Point

Gain (G

) Error

STEP Pulse Width t Blank Time t Fixed Off-Time Crossover Dead Time t

DSS

DS(On)

IN(1)

IN(0)

IN(1)

IN(0)

REF

HOME(1)

HOME(0)

PFDH

PFDL

BLANKRT

OFF

= 25°C, V

= 35 V, VDD = 3.0 to 5.5 V (unless otherwise noted)

Typ.

Max. Units

Operating 8 – 35 V During Sleep mode 0 – 35 V V

= V

OUT

Source driver, I Source driver, I

= 0 V – <1.0 –20 μA

= –2.5 A – 0.28 0.335 Ω

OUT

= 2.5 A – 0.22 0.265 Ω

OUT

– <1.0 20 μA

Source diode, IF = –2.5 A – – 1.4 V Sink diode, IF = 2.5 A – – 1.4 V f

< 50 kHz – – 8.0 mA

PWM

Operating, outputs disabled – – 6.0 mA Sleep mode – – 20 μA

Operating 3.0 5.0 5.5 V f

< 50 kHz – – 12 mA

PWM

Outputs off – – 10 mA Sleep mode – – 20 μA

0.7× V

–– VIN = 0.7 × V V

= 0.3 × V

–20 <1.0 20 μA –20 <1.0 20 μA

Operating 0 – V

––V

0.3

×V

–0±3μA I I

V V V

= –200 μA

HOME(1)

= 200 μA––

HOME(0)

0.7

× V

–

= 2 V, Phase Current = 38.27% – – ±10 %

REF

= 2 V, Phase Current = 70.71% – – ±5.0 %

REF

= 2 V, Phase Current = 100.00% – – ±5.0 %

REF

––V

0.3

× V

0.6

0.21

×V

–V –V

1––μs

= 56 kΩ, CT = 680 pF 700 950 1200 ns RT = 56 kΩ, CT = 680 pF 30 38 46 μs Synchronous rectification enabled 100 475 800 ns

Continued on the next page...

26184.23

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

A3979

DMOS Microstepping Driver with Translator

ELECTRICAL CHARACTERISTICS, continued at T

= 25°C, V

Characteristics Symbol Test Conditions Min.

Thermal Shutdown Temperature T Thermal Shutdown Hysteresis T UVLO Enable Threshold V UVLO Hysteresis V

Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for

individual units, within the specified maximum and minimum limits.

Negative current is defined as coming out of (sourcing from) the specified device pin.

EG = ( [ V

REF

/ 8] – V

SENSE

) / ( V

REF

/ 8 ).

JSD

JSDHYS

UVLO

UVLOHYS

Increasing VDD 2.45 2.7 2.95 V

= 35 V, VDD = 3.0 to 5.5 V (unless otherwise noted)

Typ.

Max. Units

– 165 – °C –15–°C

0.05 0.10 – V

26184.23

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

A3979

DMOS Microstepping Driver with Translator

THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information

Characteristic Symbol Test Conditions* Value Units

Two-layer PCB with 3.8 in.2 of copper area on each side

Package Thermal Resistance R

θJA

connected with thermal vias and to device exposed pad High-K PCB (multilayer with significant copper areas,

based on JEDEC standard)

*Additional thermal information available on Allegro Web site.

32 ºC/W

28 ºC/W

Maximum Power Dissipation, P

5.0

4.5

(W)

Power Dissipation, P

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

High-K PCB

θJA

= 28 ºC/W)

2-Layer PCB with 3.8 in

θJA

= 32 ºC/W)

copper per side

20 40 60 80 100 120 140 160

Temperature (°C)

D(max)

26184.23

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

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