ALLEGRO 3961 DATA SHEET

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3961

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

DUAL FULL-BRIDGE PWM MOTOR DRIVER

24

OUT

23

22
21
20

19
18

17

16
15
14
13

2B

E

2

SENSE
OUT

2A

V

BB2

GROUND
GROUND

I

FULL/PD

V

CC

RC

2

PHASE

ENABLE

OUT

SENSE

OUT

V

GROUND
GROUND

V

OUT

REF

V

REF

RC

PHASE

ENABLE

BB1

1

1B

2

E

1

3

1

4

1A

5
6
7
8

9

IN

10

1

11

1

12

1

Data Sheet

29319.26

3961

Designed for pulse-width modulated (PWM) current control of
bipolar stepper motors, the A3961S— is capable of continuous output
currents to ±800 mA and operating voltages to 45 V. Internal fixed
off-time PWM current-control circuitry can be used to regulate the

2

2

2

maximum load current to a desired value. An internal precision voltage
reference is provided to improve motor peak current control accuracy.
The peak load current limit is set by the user’s selection of an external
resistor divider and current-sensing resistors.

The fixed off-time pulse duration is set by user-selected external
RC timing networks. The capacitor in the RC timing network also
determines a user-selectable blanking window that prevents false
triggering of the PWM current control circuitry during switching transi­tions. This eliminates the need for two external RC filter networks on
the current-sensing comparator inputs.

Note the A3961SB (DIP) and the A3961SLB
(SOIC) are electrically identical and share a
common terminal number assignment.

selecting the appropriate source and sink driver pair. For each bridge
the ENABLE input, when held high, disables the output drivers. Special
power-up sequencing is not required. Internal circuit protection includes

For each bridge the PHASE input controls load current polarity by

ABSOLUTE MAXIMUM RATINGS

Load Supply Voltage, VBB. . . . . . . . . . 45 V

Output Current, I
Logic Supply Voltage, V
Logic Input Voltage Range,

V

. . . . . . . . . . . -0.3 V to VCC + 0.3 V

IN

Sense Voltage, V
Reference Output Current,

I

REF OUT

. . . . . . . . . . . . . . . . . . . 1.0 mA

Package Power Dissipation,

P

. . . . . . . . . . . . . . . . . . . . See Graph

D

Operating Temperature Range,

T

. . . . . . . . . . . . . . . . . -20˚C to +85˚C

A

Junction Temperature, T
Storage Temperature Range,

DISCONTINUED PRODUCT

T

. . . . . . . . . . . . . . . . -55˚C to +150˚C

S

* 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.

† Fault conditions that produce excessive

junction temperature will activate device
thermal shutdown circuitry. These conditions
can be tolerated but should be avoided.

. . . . . . . . . . ±800 mA*

OUT

. . . . . . . . . 7.0 V

CC

. . . . . . . . . . . . 1.0 V

SENSE

. . . . . . . +150˚C†

J

FOR REFERENCE ONLY

—

thermal shutdown with hysteresis, transient-suppression diodes, and
crossover-current protection.

The A3961S— is supplied in a choice of two power packages:
24-pin dual-in-line plastic package with copper heat-sink tabs and
24-lead plastic SOIC with copper heat-sink tabs. In both packages the
power tab is at ground potential and needs no electrical isolation.

FEATURES

■ ±800 mA Continuous Output Current Rating

■ 45 V Output Voltage Rating

■ Internal PWM Current Control, Saturated Sink Drivers

■ Internally Generated Precision 2.5 V Reference

■ Internal Transient-Suppression Diodes

■ Internal Thermal-Shutdown Circuitry

■ Crossover-Current Protection, UVLO Protection

Always order by complete part number:

PART NUMBER PACKAGE R

θJA

A3961SB 24-Pin DIP 40°C/W 6°C/W

A3961SLB 24-Lead SOIC 55°C/W 6°C/W

R

θJT

3961

MOTOR SUPPLY

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

5

R = 6.0°C/W

θJT

4

3

SUFFIX 'B', R = 40°C/W

2

θJA

TRUTH TABLE

ENABLE PHASE OUT

H X Off Off
LHHL
LLLH

OUT

A

B

1

SUFFIX 'LB', R = 55°C/W

0

25

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

θJA

50 75 100 125 150

TEMPERATURE IN °C

FUNCTIONAL BLOCK DIAGRAM AND TYPICAL

BIPOLAR STEPPER MOTOR APPLICATION

LOGIC SUPPLY

V

BB1

OUT

OUT

MOTOR SUPPLY 1

1A

1B

C

BB

C

cc

Dwg. GP-049A

V

cc

X = Irrelevant

GND

V

BB2

2

C

BB2

OUT

2A

OUT

2B

ENABLE 1

PHASE 1

RC

1

R

T1

CONTROL LOGIC
AND LEVEL SHIFT

BLANKING
TIME AND

SOURCE

DRIVER T

OFF

CONTROL

SENSE

C

T1

ENABLE 2

CONTROL LOGIC
AND LEVEL SHIFT

UVLO

AND

+

_

TSD

VOLTAGE

REFERENCE

BLANKING

+

_

TIME AND

SOURCE

DRIVER T

OFF

PHASE 2

RC

2

CONTROL

I

E

R

1

S1

FULL/PD

1

E

2

REF

OUT

R

1

REF

R

E

IN

2

SENSE

2

R

S2

2

C

T2

R

T2

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
Copyright ©1995, 1996, Allegro MicroSystems, Inc.

3961

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

ELECTRICAL CHARACTERISTICS at T
V, 30 k

Ω & 1000 pF RC to Ground (unless noted otherwise)

= +25°C, V

A

= 45 V, VCC = 4.75 V to 5.25 V, V

BB

SENSE

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Output Drivers

Load Supply Voltage Range V
Output Leakage Current I

Output Saturation Voltage V

Clamp Diode Forward Voltage V

BB

CEX

CE(SAT)

F

(Sink or Source) IF = 750 mA — 1.3 1.6 V

Operating, I
V

= V

OUT

V

= 0 V — <-1.0 -50 µA

OUT

Source Driver, I
Source Driver, I
Source Driver, I
Sink Driver, I
Sink Driver, I
Sink Driver, I

= ±800 mA, L = 3 mH 5.0 — 45 V

OUT

BB

= -500 mA — 1.0 1.2 V

OUT

= -750 mA — 1.1 1.3 V

OUT

= -800 mA — — 1.4 V

OUT

= +500 mA — 0.3 0.6 V

OUT

= +750 mA — 0.5 0.9 V

OUT

= +800 mA — — 1.0 V

OUT

— <1.0 50 µA

IF = 500 mA — 1.1 1.4 V

= 0

Motor Supply Current I
(No Load) I

Control Logic

Logic Supply Voltage Range V
Logic Input Voltage V

Logic Input Current I

Reference Output Voltage V

BB(ON)

BB(OFF)

CC

IN(1)

V

IN(0)

IN(1)

I

IN(0)

REF OUT

IF = 800 mA — — 1.7 V
V
V

= 0.8 V — 5.0 7.0 mA

ENABLE

= 2.4 V — 5.0 7.0 mA

ENABLE

Operating 4.75 — 5.25 V

2.4 — — V
— — 0.8 V

V

= 2.4 V — <1.0 20 µA

IN

V

= 0.8 V — <-2.0 -200 µA

IN

V

= 5.0 V, I

CC

I

FULL/PD

I

FULL/PD

= LOW 2.45 2.50 2.55 V
= HIGH 1.49 1.67 1.84 V

= 90 to 900 µA:

REF OUT

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