Datasheet 3961 Datasheet (ALLEGRO)

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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

Continued next page…

3961

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

ELECTRICAL CHARACTERISTICS at T

= +25°C, V

A

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

BB

SENSE

V, 30 kW & 1000 pF RC to Ground (unless noted otherwise) (cont.)

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Control Logic (Continued)

Reference Output Current I

REF OUT

Ref. Input Offset Current I
Comparator Input Offset Volt. V
Comparator Input Volt. Range V
PWM RC Fixed Off-time t

OFF RC

PWM Propagation Delay Time t
PWM Minimum On Time t

ON(min)

Propagation Delay Times t

OS

IO

REF

PWM

pd

3 kΩ ≤ RD = R1 + R
V

= 1 V -2.5 0 1.0 µA

REF IN

V

= 0 V -5.0 0 5.0 mV

REF

≤ 15 kΩ 90 — 900 µA

2

Operating -0.3 — 1.0 V
CT = 1000 pF, RT = 30 kΩ 27 30 33 µs
Comparator Trip to Source OFF — 1.2 2.0 µs
CT = 1000 pF ± 5%, RT ≥ 15 kΩ, VCC = 5 V — 2.5 3.6 µs
I

= ±800 mA, 50% to 90%:

OUT

ENABLE ON to Source ON — 3.2 — µs
ENABLE OFF to Source OFF — 1.2 — µs
ENABLE ON to Sink ON — 3.2 — µs

= 0

ENABLE OFF to Sink OFF — 0.7 — µs
PHASE Change to Sink ON — 3.2 — µs
PHASE Change to Source ON — 3.2 — µs
PHASE Change to Sink OFF — 0.7 — µs

PHASE Change to Source OFF — 1.2 — µs
Thermal Shutdown Temp. T
Thermal Shutdown Hysteresis ∆T

J

J

— 165 — ˚C

—15—˚C
UVLO Disable Threshold 2.5 2.7 2.9 V
UVLO Hysterisis 0.7 0.9 1.1 V
Logic Supply Current I

Logic Supply Current ∆I

CC(ON)

I

CC(OFF)

CC(ON)VENABLE1

V

ENABLE1

V

ENABLE1

= V
= V
= V

ENABLE2

ENABLE2

ENABLE2

= 0.8 V — 65 85 mA
= 2.4 V — 11 15
= 0.8 V — 0.18 — mA/˚C

Temperature Coefficient

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

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

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

3961

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

FUNCTIONAL DESCRIPTION

Internal PWM Current Control. The A3961S— contains
a fixed off-time pulse-width modulated (PWM) current­control circuit that can be used to limit the load current to
a desired value. The peak value of the current limiting
(I

) is set by the selection of an external current-sensing

TRIP

resistor (RS) and reference input voltage (V
The internal circuitry compares the voltage across the
external sense resistor to the voltage on the reference
input terminal (V

), resulting in a transconductance

REF IN

function approximated by:

V

≈

REF IN

R

S

I

TRIP

The reference input voltage is typically set with a

resistor divider from V

REF OUT

. The value of V
can be switched from a nominal value of 2.5 V to 1.67 V
by applying a low or high logic signal respectively to the
I

terminal. To ensure proper operation of the

FULL/PD

voltage reference, the resistor divider (RD = R1+R2) should
have an impedance of 3 kΩ to 15 kΩ. Within this range, a
low impedance will minimize the effect of the REF IN input
offset current.

The current-control circuitry limits the load current as

follows: when the load current reaches I

TRIP

tor resets a latch that turns off the selected source driver.
The load inductance causes the current to recirculate
through the sink driver and flyback diode.

For each bridge, the user selects an external resistor
(RT) and capacitor (CT) to determine the time period
(t

= RTCT) during which the source driver remains dis-

OFF

abled (see “RC Fixed Off-time” below). The range of rec­ommended values for CT and RT are 1000 pF to
1500 pF and 15 kΩ to 100 kΩ respectively. For optimal
load current regulation, CT is normally set to 1000 pF (see
“Load Current Regulation” below). At the end of the RC in­terval, the source driver is enabled allowing the load cur­rent to increase again. The PWM cycle repeats, maintain­ing the peak load current at the desired value.

RC BLANKING. In addition to determining the fixed off­time of the PWM control circuit, the CT component sets the
comparator blanking time. This function blanks the output
of the comparator when the outputs are switched by the

).

REF IN

REF OUT

, the compara-

[(VBB - V

I

≈

AVG

internal current-control circuitry (or by the PHASE or
ENABLE inputs). The comparator output is blanked to
prevent false over-current detections due to reverse­recovery currents of the clamp diodes, and/or switching
transients related to distributed capacitance in the load.

During internal PWM operation, at the end of the t

OFF

time, the comparator’s output is blanked and CT begins to
be charged from approximately 1.1 volts by an internal
current source of approximately 1 mA. The comparator
output remains blanked until the voltage on CT reaches
approximately 3.0 volts.

When a transition of the PHASE input occurs, C

T

is discharged to near ground during the crossover delay
time (The crossover delay time is present to prevent
simultaneous conduction of the source and sink drivers).
After the crossover delay, CT is charged by an internal cur­rent source of approximately 1 mA. The comparator out­put remains blanked until the voltage on CT reaches
approximately 3.0 volts.

When the device is disabled, via the ENABLE input,
CT is discharged to near ground. When the device is
re-enabled, CT is charged by an internal current source
of approximately 1 mA. The comparator output remains
blanked until the voltage on CT reaches approximately

3.0 volts.

The minimum recommended value for CT is
1000 pF. This value ensures that the blanking time is suffi-

cient to avoid false trips of the comparator under normal
operating conditions. For optimal regulation of the load
current, the above value for CT is recommended and the
value of RT can be sized to determine t

. For more infor-

OFF

mation regarding load current regulation, see below.
Load Current Regulation. Because the device operates

in a slow decay mode (2-quadrant PWM mode), there is a
limit to the lowest level that the PWM current control cir­cuitry can regulate load current. The limitation is due to the
minimum PWM duty cycle, which is a function of the user­selected value of t
t

max that occurs each time the PWM latch is reset.

ON(min)

and the minimum on-time pulse

OFF

If the motor is not rotating, as in the case of a stepper mo­tor in hold/detent mode, a brush dc motor when stalled or
at startup, the worst case value of current regulation can
be approximated by:

SAT(SOURCE+SINK)

1.05 (t

) t

ON(min)

max] – (1.05 (V

ON(min)

max + t

OFF

) R

LOAD

SAT(SINK)

+ VF) t

OFF

)

3961

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

where t
load, VBB is the motor supply voltage and t

= RTCT, R

OFF

is the series resistance of the

LOAD

ON(min)

max is
specified in the electrical characteristics table. When the
motor is rotating, the back EMF generated will influence
the above relationship. For brush dc motor applications,
the current regulation is improved. For stepper motor
applications when the motor is rotating, the effect is
dependent on the polarity and magnitude of the motor’s
back EMF.

The following procedure can be used to evaluate the
worst-case internal PWM load current regulation in the
system:

Set V

to 0 volts. With the load connected and

REF

the PWM current control operating in slow decay mode,
use an oscilloscope to measure the time the output is
low (sink ON) for the output that is chopping. This is the
typical minimum on time (t

typ) for the device. The

ON(min)

CT then should be increased until the measured value of
t

ON(min)

is equal to t

max as specified in the electrical

ON(min)

characteristics table. When the new value of CT has been
set, the value of RT should be decreased so the value for
t

= RTCT (with the artificially increased value of CT)

OFF

is equal to the nominal design value. The worst-case load­current regulation then can be measured in the system
under operating conditions.

PWM of the Phase and Enable Inputs. The PHASE and
ENABLE inputs can be pulse width modulated to regulate
load current. Typical propagation delays from the PHASE
and ENABLE inputs to transitions of the power outputs are
specified in the electrical characteristics table. If the inter­nal PWM current control is used, the comparator blanking
function is active during phase and enable transitions. This
eliminates false tripping of the over-current comparator
caused by switching transients (see “RC Blanking” above).

Enable PWM. Toggling the ENABLE input turns ON and
OFF the selected source and sink drivers. The corre­sponding pair of flyback and ground clamp diodes conduct
after the drivers are disabled, resulting in fast current de­cay. When the device is enabled the internal current-con­trol circuitry will be active and can be used to limit the load
current in a slow decay mode.

Phase PWM. Toggling the PHASE terminal selects which
sink/source pair is enabled, producing a load current that
varies with the duty cycle and remains continuous at all
times. This can have added benefits in bidirectional brush
dc servo motor applications as the transfer function be-

tween the duty cycle on the PHASE input and the average
voltage applied to the motor is more linear than in the case
of ENABLE PWM control (which produces a discontinuous
current at low current levels).

Miscellaneous Information. An internally generated dead
time prevents crossover currents that can occur when
switching phase.

Thermal protection circuitry turns OFF all drivers
should the junction temperature reach 165°C (typical).
This is intended only to protect the device from failures
due to excessive junction temperatures and should not
imply that output short circuits are permitted. The hyster­esis of the thermal shutdown circuit is approximately 15°C.

APPLICATION NOTES

Current Sensing. The actual peak load current (I
will be above the calculated value of I

due to delays in

TRIP

the turn off of the drivers. The amount of overshoot can be
approximated by:

(VBB – [(I

TRIP RLOAD

) + V

BEMF

]) t

PWM

IOS ≈

L

LOAD

where VBB is the motor supply voltage, V
back-EMF voltage of the load, R

LOAD

and L

BEMF

LOAD

is the

are the
resistance and inductance of the load respectively, and
t

is specified in the electrical characteristics table.

PWM

To minimize current sensing inaccuracies caused by
ground trace IR drops, each current-sensing resistor
should have a separate return to the ground terminal of the
device. For low-value sense resistors, the IR drops in the
PCB can be significant and should be taken into account.
The use of sockets should be avoided as their contact
resistance can cause variations in the effective value of
RS.

Generally, larger values of RS reduce the aforemen­tioned effects but can result in excessive heating and
power loss in the sense resistor. The selected value of R
should not cause the absolute maximum voltage rating of

1.0 V, for the SENSE terminal, to be exceeded. The
recommended value of RS is in the range of:

0.5

RS ≈

I

TRIP

± 50%

max

PEAK

)

S

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

3961

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

If desired, the reference input voltage can be filtered
by placing a capacitor from REFIN to ground. The ground
return for this capacitor as well as R2 should be indepen­dent from the high-current power-ground trace to avoid
changes in REFIN due to IR drops.

Thermal Considerations. For reliable operation it is
recommended that the maximum junction temperature be
kept below 110 to 125°C. The junction temperature can
be measured best by attaching a thermocouple to the
power tab/batwing of the device and measuring the tab
temperature, T
approximated by using the formula:

. The junction temperature can then be

TAB

TJ ≈ T

TAB

+ (I

LOAD

2 VF R

θJT

)

where VF can be chosen from the electrical specification
table for the given level of I

. The value for R

LOAD

θJT

is
given in the package thermal resistance table for the
appropriate package.

The power dissipation of the batwing packages can
be improved by 20 to 30% by adding a section of printed
circuit board copper (typically 6 to 18 square centimeters)
connected to the batwing terminals of the device.

The thermal performance in applications that run at
high load currents and/or high duty cycles can be im­proved by adding external diodes from each output to
ground in parallel with the internal diodes. Fast recovery
(≤ 200 ns) diodes should be used to minimize switching
losses.

The load supply terminal, VBB, should be decoupled
with an electrolytic capacitor (≥ 47 µF is recommended)
placed as close to the device as is physically practical.
To minimize the effect of system ground IR drops on the
logic and reference input signals the system ground should
have a low-resistance return to the motor supply voltage.

See also “Current Sensing” and “Thermal Consider­ations” above.

Fixed Off-Time Selection. With increasing values of t

OFF

switching losses will decrease, low-level load current
regulation will improve, EMI will be reduced, the PWM
frequency will decrease, and ripple current will increase.
The value of t

can be chosen for optimization of these

OFF

parameters. For applications where audible noise is a
concern, typical values of t

are chosen to be in the

OFF

range of 15 to 35 µs.

,

3961

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

24

0.280

0.240

NOTE 1

A3961SB

Dimensions in Inches

(controlling dimensions)

13

0.014

0.008

0.300

BSC

0.430

MAX

0.210

MAX

7.11

6.10

0.015

MIN

16

0.070

7

0.045

0.022

0.014

24

1

1.77

NOTE 1

67

1.15

0.100

1.280

BSC

1.230

Dimensions in Millimeters

(for reference only)

2.54

32.51

31.24

BSC

12

13

12

0.005

MIN

0.150

0.115

0.13

MIN

0.355

0.204

Dwg. MA-001-25A in

10.92

MAX

7.62

BSC

5.33

MAX

0.39

MIN

0.558

0.356

NOTES: 1. Webbed lead frame. Leads 6, 7, 18, and 19 are internally one piece.

2. Lead thickness is measured at seating plane or below.

3. Lead spacing tolerance is non-cumulative.

4. Exact body and lead configuration at vendor’s option within limits shown.

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

3.81

2.93

Dwg. MA-001-25A mm

3961

°

°

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

24 13

A3961SLB

Dimensions in Inches

(for reference only)

0.0125

0.0091

0.2992

0.2914

0.020

0.013

0.0926

0.1043

7.60

7.40

1 2

3

0.6141

0.5985

0.0040

MIN

.

Dimensions in Millimeters

(controlling dimensions)

24 13

0.050

BSC

NOTE 1
NOTE 3

0.491

0.394

0.050

0.016

0° TO 8

Dwg. MA-008-25 in

0.32

0.23

10.65

10.00

1 2

0.51

0.33

3

15.60

15.20

1.27

BSC

2.65

2.35

0.10

MIN

.

NOTES: 1. Webbed lead frame. Leads 6, 7, 18, and 19 are internally one piece.

2. Lead spacing tolerance is non-cumulative.

3. Exact body and lead configuration at vendor’s option within limits shown.

NOTE 1
NOTE 3

1.27

0.40

0° TO 8

Dwg. MA-008-25A mm

3961

DUAL FULL-BRIDGE
PWM MOTOR DRIVER

BRIDGE & HALF-BRIDGE DRIVERS

SELECTION GUIDE

IN ORDER OF 1) OUTPUT CURRENT AND 2) OUTPUT VOLTAGE

Output Ratings *

Internal Internal Part

mA V Description Diodes Outputs Protection Number †

±650 30 Dual PWM Full Bridge X Bipolar X 3966

30 Dual PWM Full Bridge X Bipolar X 3968

±750 45 Dual PWM Full Bridge X Bipolar X 2916

45 Dual PWM Full Bridge X Bipolar X 2919
45 Dual PWM Full Bridge X Bipolar X 6219

±800 33 Dual PWM Full Bridge X Bipolar X 3964

Features

±900 14 3-Ø Back-EMF Controller/Driver X DMOS X 8902-A
±1000 7.0 3-Ø Back-EMF Controller/Driver X NMOS X 8984
±1300 50 PWM Full Bridge X Bipolar X 3953
±1500 45 Dual PWM Full Bridge X Bipolar X 2917

45 Dual PWM Full Bridge X Bipolar X 2918
50 PWM Microstepping Full Bridge X
50 PWM Microstepping Full Bridge X

±2000 45 3-Ø Brushless Controller/Driver X Darlington X 2936

50 Dual Full Bridge X Darlington X 2998
50 PWM Full-Bridge X Darlington X 3951
50 PWM Full-Bridge X Darlington X 3952

±3000 45 PWM Control X Darlington – 2962
±3400 45 PWM Control X Bipolar X 2961
±4000 14 3-Ø Brushless Controller/Driver X DMOS X 8925

* Current is maximum specified test condition, voltage is maximum rating. See specification for sustaining voltage limits or over­current protection voltage limits.

† Complete part number includes additional characters to indicate operating temperature range and package style.

Darlington/Satlington™
Darlington/Satlington™

X 3955
X 3957

Allegro MicroSystems, Inc. reserves the right to make, from time to
time, such departures from the detail specifications as may be required to
permit improvements in the design of its products.

The information included herein is believed to be accurate and
reliable. However, Allegro MicroSystems, Inc. assumes no responsibility
for its use; nor for any infringements of patents or other rights of third
parties which may result from its use.

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]