Data Sheet

29319.25A

3966

DUAL FULL-BRIDGE PWM

MOTOR DRIVER

The A3966SA and A3966SLB are designed to drive both windings of a

two-phase bipolar stepper motor. Each device includes two H-bridges
capable of continuous output currents of

ą650 mA and operating voltages to

30 V. Motor winding current can be controlled by the internal fixed-fre-
quency, pulse-width modulated (PWM), current-control circuitry. The peak
load current limit is set by the user's selection of a reference voltage and
current-sensing resistors. Except for package style and pinout, the two
devices are identical.

The fixed-frequency pulse duration is set by a user-selected external

RC timing network. 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.

To reduce on-chip power dissipation, the H-bridge power outputs have

been optimized for low saturation voltages. The sink drivers feature Allegro's
patented SatlingtonTM output structure. The Satlington outputs combine the
low voltage drop of a saturated transistor and the high peak current capability
of a Darlington.

For each bridge, a PHASE input controls load-current polarity by

selecting the appropriate source and sink driver pair. For each bridge, an
ENABLE input, when held high, disables the output drivers. Special power-
up sequencing is not required. Internal circuit protection includes thermal
shutdown with hysteresis, ground-clamp and flyback diodes, and crossover-
current protection.

The A3966SA is supplied in a 16-pin dual in-line plastic package. The

A3966SLB is supplied in a 16-lead plastic SOIC with copper heat sink tabs.
The power tab is at ground potential and needs no electrical isolation.

A3966SLB

OUT

GROUND

Dwg. PP-066-1

GROUND

OUT

PHASE

OUT

SENSE

ENABLE

LOAD

SUPPLY

REFERENCE

PHASE

ENABLE

SENSE

OUT

LOGIC
SUPPLY

LOGIC

REF

FEATURES

I ą650 mA Continuous Output Current
I 30 V Output Voltage Rating

I Internal Fixed-Frequency PWM Current Control

I SatlingtonTM Sink Drivers
I User-Selectable Blanking Window

I Internal Ground-Clamp & Flyback Diodes

I Internal Thermal-Shutdown Circuitry
I Crossover-Current Protection and UVLO Protection

Always order by complete part number:

Part Number

Package

A3966SA

16-pin DIP

°C/W

A3966SLB

16-lead batwing SOIC

°C/W

ABSOLUTE MAXIMUM RATINGS

Load Supply Voltage, V

...................... 30 V

Output Current, I

OUT

(peak) ...........

750 mA

(continuous) ..............................

650 mA

Logic Supply Voltage, V

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

Input Voltage, V

........ -0.3 V to V

+ 0.3 V

Sense Voltage, V

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

Package Power Dissipation (T

= 25

°C), P

A3966SA ..................................... 2.08 W*
A3966SLB ................................... 1.87 W*

Operating Temperature Range,

..................................... -20

C to +85

Junction Temperature,

.................................................. +150

Storage Temperature Range,

................................... -55

C to +150

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.

* Per SEMI G42-88 Specification, Thermal Test Board
Standardization for Measuring Junction-to-Ambient
Thermal Resistance of Semiconductor Packages

3966
DUAL FULL-BRIDGE
PWM MOTOR DRIVER

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

FUNCTIONAL BLOCK DIAGRAM

OUT

GROUND

Dwg. PP-066-2

OUT

PHASE

OUT

SENSE

ENABLE

LOAD

SUPPLY

REFERENCE

PHASE

ENABLE

SENSE

OUT

LOGIC

SUPPLY

REF

GROUND

LOGIC

A3966SA

TRUTH TABLE

PHASE

ENABLE

OUT

Off

X = Irrelevant

R2S

R1S

REFERENCE

÷4

V CC

LOGIC

SUPPLY

PHASE

LOAD

SUPPLY

OUT

V BB

R T

C T

Dwg. FP-036-6

SENSE

UVLO
& TSD

BLANKING

GATE

PWM LATCH

CURRENT-SENSE

COMPARATOR

ENABLE

OSC

PHASE2

GROUND

SENSE

UVLO
& TSD

BLANKING

GATE

PWM LATCH

CURRENT-SENSE

COMPARATOR

ENABLE 2

CONTROL LOGIC

SOURCE

ENABLE

OUT

CONTROL LOGIC

SOURCE

ENABLE

3966

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

www.allegromicro.com

Load Supply Voltage Range

Operating, I

OUT

ą650 mA, L = 3 mH

Output Leakage Current

CEX

OUT

= 30 V

<1.0

ľA

OUT

= 0 V

<-1.0

-50

ľA

Output Saturation Voltage

CE(SAT)

Source Driver, I

OUT

= -400 mA

1.72.0

Source Driver, I

OUT

= -650 mA

1.8

2.1

Sink Driver, I

OUT

= +400 mA, V

= 0.5 V

0.3

0.5

Sink Driver, I

OUT

= +650 mA, V

= 0.5 V

0.4

1.3

Clamp Diode Forward Voltage

= 400 mA

1.1

1.4

= 650 mA

1.4

1.6

Motor Supply Current

BB(ON)

ENABLE1

= V

ENABLE2

= 0.8 V

3.0

5.0

(No Load)

BB(OFF)

ENABLE1

= V

ENABLE2

= 2.4 V

<1.0

200

ľA

ELECTRICAL CHARACTERISTICS at T

= +25

C, V

= 30 V, V

= 4.75 V to 5.5 V, V

REF

= 2 V,

= 0 V, 56 k

& 680 pF RC to Ground (unless noted otherwise)

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Output Drivers

Logic Supply Voltage Range

Operating

4.75

5.50

Logic Input Voltage

IN(1)

2.4

IN(0)

0.8

Logic Input Current

IN(1)

= 2.4 V

<1.0

ľA

IN(0)

= 0.8 V

<-20

-200

ľA

Reference Input Volt. Range

REF

Operating

0.1

2.0

Reference Input Current

REF

-2.5

1.0

ľA

Reference Divider Ratio

REF

TRIP

3.8

4.0

4.2

Current-Sense Comparator

REF

= 0 V

-6.0

6.0

Input Offset Voltage

Current-Sense Comparator

Operating

-0.3

1.0

Input Voltage Range

Sense-Current Offset

OUT

, 50 mA

OUT

650 mA

Control Logic

NOTES:1. Typical Data is for design information only.

2. Negative current is defined as coming out of (sourcing) the specified device terminal.

3966
DUAL FULL-BRIDGE
PWM MOTOR DRIVER

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

PWM RC Frequency

osc

= 680 pF, R

= 56 k

22.9

25.4

27.9

kHz

PWM Propagation Delay Time

PWM

Comparator Trip to Source OFF

1.0

1.4

ľs

Cycle Reset to Source ON

0.8

1.2

ľs

Cross-Over Dead Time

codt

1 k

Load to 25 V

0.2

1.8

3.0

ľs

Propagation Delay Times

OUT

ą650 mA, 50% to 90%:

ENABLE ON to Source ON

100

ENABLE OFF to Source OFF

500

ENABLE ON to Sink ON

200

ENABLE OFF to Sink OFF

200

PHASE Change to Sink ON

2200

PHASE Change to Sink OFF

200

PHASE Change to Source ON

2200

PHASE Change to Source OFF

200

Thermal Shutdown Temp.

165

°C

Thermal Shutdown Hysteresis

°C

UVLO Enable Threshold

T(UVLO)+

Increasing V

4.1

4.6

UVLO Hysteresis

T(UVLO)hys

0.1

0.6

Logic Supply Current

CC(ON)

ENABLE 1

= V

ENABLE 2

= 0.8 V

CC(OFF)

ENABLE 1

= V

ENABLE 2

= 2.4 V

9.0

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

ELECTRICAL CHARACTERISTICS at T

= +25

C, V

= 30 V, V

= 4.75 V to 5.5 V, V

REF

= 2 V,

= 0 V, 56 k

& 680 pF RC to Ground (unless noted otherwise) (cont.)

Control Logic (continued)

NOTES:1. Typical Data is for design information only.

2. Negative current is defined as coming out of (sourcing) the specified device terminal.

3966

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

www.allegromicro.com

Internal PWM Current Control. The A3966SA and
A3966SLB dual H-bridges are designed to drive both
windings of a bipolar stepper motor. Load current can be
controlled in each motor winding by an internal fixed-
frequency PWM control circuit. The current-control
circuitry works as follows: when the outputs of the H-
bridge are turned on, current increases in the motor wind-
ing. The load current is sensed by the current-control
comparator via an external sense resistor (R

). Load

current continues to increase until it reaches the predeter-
mined value, set by the selection of external current-
sensing resistors and reference input voltage (V

REF

)

according to the equation:

TRIP

= I

OUT

+ I

= V

REF

/(4 R

)

where I

is the sense-current error (typically 18 mA) due

to the base-drive current of the sink driver transistor.

At the trip point, the comparator resets the source-

enable latch, turning off the source driver of that H-bridge.
The source turn off of one H-bridge is independent of the
other H-bridge. Load inductance causes the current to
recirculate through the sink driver and ground-clamp
diode. The current decreases until the internal clock
oscillator sets the source-enable latches of both H-bridges,
turning on the source drivers of both bridges. Load current
increases again, and the cycle is repeated.

FUNCTIONAL DESCRIPTION

The frequency of the internal clock oscillator is set by

the external timing components R

. The frequency can

be approximately calculated as:

osc

= 1/(R

+ t

blank

)

where t

blank

is defined below.

The range of recommended values for R

and C

are

20 k

to 100 k and 470 pF to 1000 pF respectively.

Nominal values of 56 k

and 680 pF result in a clock

frequency of 25 kHz.

Current-Sense Comparator Blanking. When the
source driver is turned on, a current spike occurs due to
the reverse-recovery currents of the clamp diodes and
switching transients related to distributed capacitance in
the load. To prevent this current spike from erroneously
resetting the source enable latch, the current-control
comparator output is blanked for a short period of time
when the source driver is turned on. The blanking time is
set by the timing component C

according to the equa-

tion:

blank

= 1900 C

(

ľs).

A nominal C

value of 680 pF will give a blanking

time of 1.3

ľs.

The current-control comparator is also blanked when

the H-bridge outputs are switched by the PHASE or
ENABLE inputs. This internally generated blank time is
approximately 1

ľs.

Dwg. WM-003-2

PHASE

OUT

TRIP

blank

INTERNAL

OSCILLATOR

BRIDGE

SOURCE
OFF

BRIDGE

R C

T T

ALL

OFF

Dwg. EP-006-16

R S

BRIDGE ON

SOURCE OFF

ALL OFF

Part Number 3966