Data Sheet

29319.1B

FULL-BRIDGE PWM MOTOR DRIVER

Designed for bidirectional pulse-width modulated current control of

inductive loads, the A3952S is capable of continuous output currents
to

2 A and operating voltages to 50 V. Internal fixed off-time PWM

current-control circuitry can be used to regulate the maximum load
current to a desired value. The peak load current limit is set by the
user's selection of an input reference voltage and external sensing
resistor. The fixed OFF-time pulse duration is set by a user-selected
external RC timing network. Internal circuit protection includes thermal
shutdown with hysteresis, transient suppression diodes, and crossover-
current protection. Special power-up sequencing is not required.

With the ENABLE input held low, the PHASE input controls load

current polarity by selecting the appropriate source and sink driver pair.
The MODE input determines whether the PWM current-control circuitry
operates in a slow current-decay mode (only the selected sink driver
switching) or in a fast current-decay mode (selected source and sink
switching). A user-selectable blanking window prevents false triggering
of the PWM current control circuitry. With the ENABLE input held high,
all output drivers are disabled. A sleep mode is provided to reduce
power consumption when inactive.

When a logic low is applied to the BRAKE input, the braking

function is enabled. This overrides ENABLE and PHASE to turn OFF
both source drivers and turn ON both sink drivers. The brake function
can be safely used to dynamically brake brush dc motors.

The A3952S is supplied in a choice of three power packages. In

all package styles, the batwing is at ground potential and needs no
isolation. These devices are also available for operation from -40

C to

+125

C. To order, change the suffix from 'S' to 'K'.

FEATURES

2 A Continuous Output Current Rating

50 V Output Voltage Rating

Internal PWM Current Control

Fast and Slow Current-Decay Modes

Sleep (Low Current Consumption) Mode

Internal Transient Suppression Diodes

Under-Voltage Lockout

Internal Thermal Shutdown Circuitry

Crossover-Current Protection

Always order by complete part number:

Part Number

Package

A3952SB

16-Pin DIP

C/W

6.0

C/W

A3952SEB

28-Lead PLCC

C/W

6.0

C/W

A3952SLB

16-Lead SOIC

C/W

6.0

C/W

A3952SB

Note that the A3952SB (DIP) and the A3952SLB
(SOIC) are electrically identical and share a
common terminal number assignment.

ABSOLUTE MAXIMUM RATINGS

Load Supply Voltage, V

.................. 50 V

Output Current, I

OUT

s) ..................................

3.5 A

(Continuous) ...............................

2.0 A

Logic Supply Voltage, V

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

Logic Input Voltage Range,

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

+ 0.3 V

Sense Voltage, V

SENSE

...................... 1.5 V

Reference Voltage, V

REF

.................... 15 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 limited by duty cycle,
ambient temperature, heat sinking and/or forced
cooling. Under any set of conditions, do not
exceed the specified current rating or a junction
temperature of +150

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

3952

MODE

GROUND

LOGIC

SUPPLY

PHASE

GROUND

SENSE

LOAD
SUPPLY

Dwg. PP-056

BRAKE

REF

LOAD
SUPPLY

OUTB

OUTA

LOGIC

ENABLE

3952
FULL-BRIDGE
PWM MOTOR DRIVER

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

FUNCTIONAL BLOCK DIAGRAM

TRUTH TABLE

BRAKE

ENABLE PHASE

MODE

OUT

DESCRIPTION

Sleep Mode

Standby, Note 1

Forward,
Fast-Decay Mode

Forward,
Slow-Decay Mode

Reverse,
Fast-Decay Mode

Reverse,
Slow-Decay Mode

Brake,
Fast-Decay Mode

Brake, No Current
Control, Note 2

X = Irrelevant

Z = High Impedance (source and sink both OFF)

NOTES:

1. Includes active pull-offs for power outputs.
2. Includes internal default V

sense

level for over-current protection.

LOGIC

SUPPLY

LOAD

SUPPLY

PHASE

EMITTERS

UVLO

& TSD

R S

Dwg. FP-036A

MODE

REF

OUT

ENABLE

SENSE

BRAKE

INPUT LOGIC

GROUND

1.5 V

PWM LATCH

BLANKING

SLEEP &
STANDBY MODES

VTH

'EB' ONLY

'B' & 'LB'
PACKAGES

R T

C T

100

125

150

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

TEMPERATURE IN

°
°
°
°

R = 6

C/W

Dwg. GP-004-2B

SUFFIX 'EB', R = 36

C/W

SUFFIX 'B', R = 43

C/W

SUFFIX 'LB', R = 90

C/W

3952

FULL-BRIDGE

PWM MOTOR DRIVER

www.allegromicro.com

A3952SEB

ELECTRICAL CHARACTERISTICS at T

= +25

C, V

= 50 V, V

= 5.0 V, V

BRAKE

= 2.0 V,

SENSE

= 0 V, RC = 20 k

/1000 pF to Ground (unless noted otherwise).

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Output Drivers

Load Supply Voltage Range

Operating, I

OUT

2.0 A, L = 3 mH

Output Leakage Current

CEX

OUT

= V

<1.0

OUT

= 0 V

<-1.0

-50

Output Saturation Voltage

CE(SAT)

Source Driver, I

OUT

= -0.5 A

0.9

1.2

Source Driver, I

OUT

= -1.0 A

1.0

1.4

Source Driver, I

OUT

= -2.0 A

1.2

1.8

Sink Driver, I

OUT

= +0.5 A

0.9

1.2

Sink Driver, I

OUT

= +1.0 A

1.0

1.4

Sink Driver, I

OUT

= +2.0 A

1.3

1.8

Clamp Diode Forward Voltage

= 0.5 A

1.0

1.4

(Source or Sink)

= 1.0 A

1.1

1.6

= 2.0 A

1.4

2.0

Load Supply Current

BB(ON)

ENABLE

= 0.8 V

2.9

6.0

(No Load)

BB(OFF)

ENABLE

= 2.0 V, V

MODE

= 0.8 V

3.1

6.5

BRAKE

= 0.8 V

3.1

6.5

BB(SLEEP)

ENABLE

= V

MODE

= 2.0 V

<1.0

GROUND

Dwg. PP-057

CONNECTION

EMITTERS

LOAD

SUPPLY

REF

LOGIC

BRAKE

LOGIC

SUPPLY

PHASE

ENABLE

MODE

SENSE

LOAD

SUPPLY

OUT

Continued next page ...

3952
FULL-BRIDGE
PWM MOTOR DRIVER

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

Control Logic

Logic Supply Voltage Range

Operating

4.5

5.0

5.5

Logic Input Voltage

IN(1)

2.0

IN(0)

0.8

Logic Input Current

IN(1)

= 2.0 V

<1.0

IN(0)

= 0.8 V

<-2.0

-200

Reference Voltage Range

REF

Operating

Reference Input Current

REF

= 2.0 V

Reference Voltage Divider Ratio

REF

= 15 V

9.5

10.0

10.5

Comparator Input Offset Voltage

REF

= 0 V

1.0

PWM RC Fixed OFF Time

off

= 1000 pF, R

= 20 k

PWM Minimum ON Time

on(min)

= 820 pF, R

12 k

1.7

3.0

= 1200 pF, R

12 k

2.5

3.8

Propagation Delay Time

OUT

2.0 A, 50% E

to 90% E

OUT

Transition:

ENABLE ON to Source ON

2.9

ENABLE OFF to Source OFF

0.7

ENABLE ON to Sink ON

2.4

ENABLE OFF to Sink OFF

0.7

PHASE Change to Source ON

2.9

PHASE Change to Source OFF

0.7

PHASE Change to Sink ON

2.4

PHASE Change to Sink OFF

0.7

pd(pwm)

Comparator Trip to Sink OFF

0.8

1.5

Thermal Shutdown Temperature

165

Thermal Shutdown Hysteresis

UVLO Disable Threshold

CC(UVLO)

3.15

3.50

3.85

UVLO Hysteresis

CC(UVLO)

300

400

500

Logic Supply Current

CC(ON)

ENABLE

= 0.8 V, V

BRAKE

= 2.0 V

(No Load)

CC(OFF)

ENABLE

= 2.0 V, V

MODE

= 0.8 V

CC(BRAKE)

BRAKE

= 0.8 V

CC(SLEEP)

ENABLE

= V

MODE

= V

BRAKE

= 2.0 V

3.0

5.0

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

2. Each driver is tested separately.
3. Negative current is defined as coming out of (sourcing) the specified device terminal.

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

3952

FULL-BRIDGE

PWM MOTOR DRIVER

www.allegromicro.com

FUNCTIONAL DESCRIPTION

INTERNAL PWM CURRENT CONTROL DURING
FORWARD AND REVERSE OPERATION

The A3952S contains a fixed OFF-time pulse-width

modulated (PWM) current-control circuit that can be used
to limit the load current to a desired value. The value of
the current limiting (I

TRIP

) is set by the selection of an

external current sensing resistor (R

) and reference input

voltage (V

REF

). The internal circuitry compares the voltage

across the external sense resistor to one tenth the voltage
on the REF input terminal, resulting in a function approxi-
mated by

TRIP

= V

REF

/(10R

In forward or reverse mode the current-control circuitry

limits the load current. When the load current reaches
I

TRIP

, the comparator resets a latch to turn OFF the

selected sink driver (in the slow-decay mode) or selected
sink and source driver pair (in the fast-decay mode). In
slow-decay mode, the selected sink driver is disabled; the
load inductance causes the current to recirculate through
the source driver and flyback diode (see figure 1). In fast-
decay mode, the selected sink and source driver pair are
disabled; the load inductance causes the current to flow
from ground to the load supply via the ground clamp and
flyback diodes.

Figure 1 -- Load-Current Paths

The user selects an external resistor (R

) and capaci-

tor (C

) to determine the time period (t

off

= R

) during

which the drivers remain disabled (see "RC Fixed OFF
Time" below). At the end of the R

interval, the drivers

are re-enabled allowing the load current to increase again.
The PWM cycle repeats, maintaining the load current at
the desired value (see figure 2).

ENABLE

MODE

LOAD

CURRENT

TRIP

Dwg. WP-015-1

Dwg. EP-006-2A

R S

DRIVE CURRENT

RECIRCULATION
(SLOW-DECAY MODE)

RECIRCULATION
(FAST-DECAY MODE)

Figure 2 -- Fast and Slow Current-Decay Waveforms

INTERNAL PWM CURRENT CONTROL DURING
BRAKE MODE OPERATION

The brake circuit turns OFF both source drivers and

turns ON both sink drivers. For dc motor applications, this
has the effect of shorting the motor's back-EMF voltage,
resulting in current flow that brakes the motor dynamically.
However, if the back-EMF voltage is large, and there is no
PWM current limiting, then the load current can increase to
a value that approaches a locked rotor condition. To limit
the current, when the I

TRIP

level is reached, the PWM

circuit disables the conducting sink driver. The energy
stored in the motor's inductance is then discharged into
the load supply causing the motor current to decay.

As in the case of forward/reverse operation, the drivers

are re-enabled after a time given by t

off

= R

(see "RC

Fixed OFF Time" below). Depending on the back-EMF
voltage (proportional to the motor's decreasing speed), the
load current again may increase to I

TRIP

. If so, the PWM

cycle will repeat, limiting the load current to the desired
value.

Brake Operation - MODE Input High

During braking, when the MODE input is high, the

current limit can be approximated by

TRIP

= V

REF

/(10R

CAUTION: Because the kinetic energy stored in the

motor and load inertia is being converted into current,
which charges the V

supply bulk capacitance (power

supply output and decoupling capacitance), care must be
taken to ensure the capacitance is sufficient to absorb the
energy without exceeding the voltage rating of any devices
connected to the motor supply.

Part Number A3952S