DISCONTINUED PRODUCT

-- FOR REFERENCE ONL

The UDN2961B and UDN2961W are 3.4 A half bridges designed

specifically for driving solenoid printheads, stepper motors, and dc
motors. The UDN2961B/W consists of a power source driver output,
a power sink driver output, a flyback recovery diode, internal current
sensing circuitry, and a user-selectable fixed off-time chopper circuit.

The output drivers are capable of sustaining 45 V with continuous

currents of

3.4 A and peak transient currents of

4 A permitted. The

outputs have been optimized for a low output saturation voltage
(typically 2.6 V total source plus sink drops at 3.4 A).

For output current control, load current is sensed internally and

limited by chopping the output driver(s) in a user-selectable fixed off-
time PWM mode. The maximum output current is determined by the
user's selection of a reference voltage. The MODE pin determines
whether the current control circuitry will chop in a slow current-decay
mode (only the source driver switching) or in a fast current-decay
mode (source and sink switching). A user-selectable blanking window
prevents false triggering of the current control circuitry during
chopping.

The UDN2961B is supplied in a 16-pin dual in-line plastic batwing

package with a copper lead-frame and heat sinkable tabs for improved
power dissipation capabilities. For higher power dissipation require-
ments, the UDN2961W is supplied in a 12-pin single in-line power tab
package.

FEATURES

3.4 A, 45 V Source and Sink Drivers

Internal Current Sensing

User-Selectable Fixed Off-Time PWM Current Control

Internal Flyback Diode

Low Output Saturation Voltage

Chip Enable

Fast or Slow Current-Decay Modes

Programmable Blanking Window

Internal Thermal Shutdown Circuitry

UDN2961B

HIGH-CURRENT HALF-BRIDGE

PRINTHEAD/MOTOR DRIVER--WITH INTERNAL

CURRENT SENSING AND CONTROL

ABSOLUTE MAXIMUM RATINGS

Supply Voltage, V

. . . . . . . . . . . . . . 45 V

Output Current, I

OUT

(continuous) .

3.4 A

s, 10% duty cycle) . .

4.0 A

Logic Supply Voltage, V

. . . . . . . . . 7.0 V

Input Voltage Range,

. . . . . . . . . . . . . . . -0.3 V to +7.0 V

Package Power Dissipation,

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

Operating Temperature Range,

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

C to +85

Junction Temperature, T

. . . . . . . +150

Storage Temperature Range,

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

C to +150

Output current rating may be restricted to a value
determined by system concerns and factors.
These include: system duty cycle and timing,
ambient temperature, and use of any heatsinking
and/or forced cooling. For reliable operation, the
specified maximum junction temperature should
not be exceeded.

* Fault conditions that produce excessive junction
temperature will activate device thermal shutdown
circuitry. These conditions can be tolerated, but
should be avoided.

Always order by complete part number:

Part Number Package

UDN2961B

16-Pin DIP

UDN2961W

12-Pin Power-Tab SIP

SOURCE OUT

EMITTER

SINK OUT

GROUND

ENABLE

MODE

GROUND

REF

INPUT

CURRENT-

CONTROL

LOGIC

LOAD SUPPLY

LOGIC SUPPLY

Dwg. PP-035

Data Sheet

29318.16*

2961

2961
HIGH-CURRENT
HALF-BRIDGE
PRINTHEAD/MOTOR DRIVER

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

FUNCTIONAL BLOCK DIAGRAM

100

125

150

TEMPERATURE IN

°
°
°
°

Dwg. GP-032A

SUFFIX 'B', R = 43

C/W

SUFFIX 'W', R = 38

C/W

SUFFIX 'W',

R = 2.0

C/W

SUFFIX 'B',

R = 6.0

C/W

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

UDN2961W

2940

TSD

LOW
TRIP

SOURCE OUT

EMITTER

SINK OUT

ENABLE

INPUT

MODE

GROUND

FLIP-

FLOP

REF

CIRCUIT

REF

+5 V

SENSE

ONE

SHOT

Dwg. FP-019A

EMITTER

INPUT

ENABLE

MODE

SOURCE OUT

GROUND

SINK OUT

CURRENT-

CONTROL

LOGIC

LOGIC SUPPLY

LOAD SUPPLY

REF

Dwg. PP-036

2961

HIGH-CURRENT

HALF-BRIDGE

PRINTHEAD/MOTOR DRIVER

www.allegromicro.com

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Output Drivers

Output Leakage Current

CEX

= 0.8 V, V

SOURCE

= 0 V

<-1.0

-100

= 0.8 V, V

SINK

= 45 V

<1.0

100

Output Saturation Voltage

CE(SAT)

Source Driver, I

OUT

= -3.4 A

1.6

2.2

Source Driver, I

OUT

= -3.0 A

1.5

Sink Driver, I

OUT

= 3.4 A

1.0

1.4

Sink Driver, I

OUT

= 3.0 A

0.9

Output Sustaining Voltage

CE(sus)

OUT

3.4 A, L = 3 mH

Recovery Diode Leakage Current

= 45 V

<1.0

100

Recovery Diode Forward Voltage

= 3.4 A

2.0

Motor Supply Current

BB(on)

= 2.0 V, V

= 0.8 V, No Load

BB(off)

= 0.8 V

2.5

Output Rise Time

Source Driver, I

OUT

= -3.4 A

600

Sink Driver, I

OUT

= 3.4 A

600

Output Fall Time

Source Driver, I

OUT

= -3.4 A

600

Sink Driver, I

OUT

= 3.4 A

600

Control Logic

Logic Input Voltage

IN(1)

2.0

IN(0)

0.8

Logic Input Current

IN(1)

= 5.0 V

IN(0)

= 0 V

-1.0

Reference Input Current

REF

= 5.0 V

Transconductance

TRIP

REF

= 1.0 V

0.9

1.0

1.1

A/V

REF

= 3.2 V

0.9

1.0

1.1

A/V

Logic Supply Current

= 2.0 V, V

= 0.8 V, No Load

160

= 0.8 V

Turn On Delay

pd(on)

Source Driver

600

Sink Driver

600

Turn Off Delay

pd(off)

Source Driver

2.0

Sink Driver

2.0

Thermal Shutdown Temperature

165

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

ELECTRICAL CHARACTERISTICS at T

= +25

C, V

= 45 V,

= 4.75 V to 5.25 V, R

= 2940

(unless otherwise noted).

2961
HIGH-CURRENT
HALF-BRIDGE
PRINTHEAD/MOTOR DRIVER

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

SENSE

REF

CIRCUIT

Dwg. EP-037

DRIVE CURRENT

RECIRCULATION (SLOW-DECAY MODE)

RECIRCULATION (FAST-DECAY MODE)

APPLICATIONS INFORMATION

The UDN2961B/W is a high current

half-bridge designed to drive a number of
inductive loads such as printer solenoids,
stepper motors, and dc motors. Load current
is sensed internally and is controlled by
pulse-width modulating (PWM) the output
driver(s) in a fixed off-time, variable-
frequency format. The peak current level is
set by the user's selection of a reference
voltage. A slow current-decay mode
(chopping only the source driver) or a fast
current-decay mode (chopping both the
source and sink drivers) can be selected via
the MODE pin.

PWM CURRENT CONTROL

A logic low on the MODE pin sets the

current-control circuitry into the slow-decay
mode. The RS flip-flop is set initially, and
both the source driver and the sink driver are
turned ON when the INPUT pin is at a logic
low. As current in the load increases, it is
sensed by the internal sense resistor until the
sense voltage equals the trip voltage of the
comparator. At this time, the flip-flop is reset
and the source driver is turned OFF. Over the
range of V

REF

= 0.8 V to 3.4 V, the output

current trip point transfer function is a direct
linear function of the reference voltage:

TRIP

= V

REF

To ensure an accurate chop current level

(

10%), an external 2940

1% resistor

) is used. The actual load current peak

will be slightly higher than the trip point
(especially for low-inductance loads) because
of the internal logic and switching delays
(typically 1.5

s). After the source driver turns

OFF, the load current decays, circulating
through an external ground clamp diode, the
load, and the sink transistor. The source
driver's OFF time (and therefore the magni-
tude of the current decrease) is determined
by the one-shot's external RC timing compo-
nents:

OFF

= RC

within the range of 20 k

to 100 k

and 100 pF to 1000 pF. When the

one-shot times out, the flip-flop is set again, the source driver is re-
enabled, and the load current again is allowed to rise to the set peak
value and trip the comparator. This cycle repeats itself, maintaining the
average load current at the desired level.

ENABLE

INPUT

MODE

LOAD

CURRENT

RC/2

TRIP

Dwg. WP-015

2961

HIGH-CURRENT

HALF-BRIDGE

PRINTHEAD/MOTOR DRIVER

www.allegromicro.com

A logic high on the MODE pin sets the

current-control circuitry into the fast-decay
mode. When the peak current threshold is
detected, the flip-flop is reset and both the
source driver and the sink driver turn OFF.
Load current decays quickly through the
external ground clamp diode, the load, and
the internal flyback diode. In the fast-
decay mode, the OFF time period is one-
half the time that is set by the external RC
network for the slow-decay mode:

OFF

The amount of ripple current, when

chopping in the fast-decay mode, is
considerably higher than when chopping in
the slow-decay mode.

The frequency of the PWM current

control is determined by the time required
for the load current to reach the set peak
threshold (a function of the load character-
istics and V

) plus the OFF time of the

switching driver(s) (set by the external RC
components).

To prevent false resetting of the flip-

flop, due to switching transients and noise,
a blanking time for the comparator can be
set by the user where t

3600 x C in the

slow-decay mode or t

2400 x C in the

fast-decay mode. For C between 100 pF
and 1000 pF, t

is in

POWER CONSIDERATIONS

The UDN2961B/W outputs are opti-

mized for low power dissipation. The sink
driver has a maximum saturation voltage
drop of only 1.4 V at 3.4 A, while the
source driver has a 2.2 V drop at -3.4 A.
Device power dissipation is minimized in
the slow-decay mode, as the chopping
driver (the source driver) is ON for less
than 50% of the chop period. When the
source driver is OFF during a chop cycle,
power is dissipated on chip only by the sink
driver; the rest of the power is dissipated
through the external ground clamp diode.
In the fast-decay mode, the ON time of the
chopping drivers (both the source driver

and the sink driver) may be greater than 50%, and the power dissipa-
tion will be greater.

GENERAL

A logic low on the ENABLE pin prevents the source driver and the

sink driver from turning ON, regardless of the state of the INPUT pin or
the supply voltages. With the ENABLE pin high, a logic low on the
INPUT pin turns ON the output drivers.

To protect against inductive load voltage transients, an external

ground clamp diode is required. A fast-recovery diode is recom-
mended to reduce power dissipation in the UDN2961B/W. The blank-
ing time prevents false triggering of the current sense comparator,
which can be caused by the recovery current spike of the ground
clamp diode when the chopping source driver turns ON.

CURRENT-

CONTROL

LOGIC

CURRENT-

CONTROL

LOGIC

2940

REF

INPUT

ENABLE

MODE

Dwg. EP-038A

+5 V

INPUT

2940

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