A3962 - Allegro MicroSystems, Inc.

3962

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

DISCONTINUED PRODUCT

FOR REFERENCE ONLY

— See A3964SLB

DUAL FULL-BRIDGE PWM MOTOR DRIVER

Always order by complete part number: A3962SLB .

ABSOLUTE MAXIMUM RATINGS

Load Supply Voltage, VBB . . . . . . . . . 30 V

Output Current, IOUT . . . . . . . . . . ±800 mA*

Logic Supply Voltage, VCC . . . . . . . . . 7.0 V

Logic Input Voltage Range,

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

Sense Voltage, VSENSE . . . . . . . . . . . . 1.0 V

Reference Output Current,

IREF OUT . . . . . . . . . . . . . . . . . . . 1.0 mA

Package Power Dissipation,

PD. . . . . . . . . . . . . . . . . . . . See Graph

Operating Temperature Range,

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

Junction Temperature, TJ. . . . . . . +150˚C†

Storage Temperature Range,

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

* 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 tempera

ture of 150˚C.

† Fault conditions that produce excessive junction

temperature will activate the device’s thermal

shutdown circuitry. These conditions can be

tolerated but should be avoided.

Data Sheet

29319.27

Designed for pulse-width modulated (PWM) current control of

bipolar stepper motors, the A3962SLB is capable of continuous output

currents to ±800 mA and operating voltages to 30 V. Internal fixed

off-time PWM current-control circuitry can be used to regulate the

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 transi-

tions. This eliminates the need for two external RC filter networks on

the current-sensing comparator inputs.

For each bridge the PHASE input controls load current polarity by

selecting the appropriate source and sink driver pair. For each bridge

the ENABLE input, when held high, disables the output drivers. Spe-

cial power-up sequencing is not required. Internal circuit protection

includes thermal shutdown with hysteresis, transient-suppression

diodes, and crossover-current protection.

The A3962SLB is supplied in a 20-lead plastic SOIC with copper

heat sink tabs. The power tab is at ground potential and needs no

electrical isolation.

FEATURES

■±800 mA Continuous Output Current Rating

■30 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

■Automotive Capable

3962

PWM 1

PWM 2

GROUND

GROUND GROUND

GROUND

PHASE

REF(OUT)

REF(IN)

PHASE

OUT

SENSE

OUT

SENSE

OUT

LOAD

SUPPLY LOGIC

SUPPLY

Dwg. PP-047-1

ENABLE

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

3962

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

FUNCTIONAL BLOCK DIAGRAM AND TYPICAL

BIPOLAR STEPPER MOTOR APPLICATION

TRUTH TABLE

ENABLE PHASE OUTAOUTB

H X Off Off

LHHL

LLLH

X = Irrelevant

50 75 100 125 150

2.5

1.5

1.0

0.5

TEMPERATURE in °C

2.0

R = 6°C/W

θJT

R = 60°C/W

θJA

ALLOWABLE PACKAGE POWER DISSIPATION in WATTS

Dwg. GP-019-1

MOTOR SUPPLY

OUT

ENABLE 1

PHASE 1 CONTROL LOGIC

AND LEVEL SHIFT

OUT

BB BB

CC CC

OUT

ENABLE 2

PHASE 2

OUT

RC SENSE

T1 T1 S1

GND REF

RRRRC

S2 T2

OUT IN

REF SENSE

BLANKING

TIME AND

SOURCE

DRIVER T

CONTROL

OFF

UVLO

AND

TSD

CONTROL LOGIC

AND LEVEL SHIFT

BLANKING

TIME AND

SOURCE

DRIVER T

CONTROL

OFF

VOLTAGE

REFERENCE

LOGIC SUPPLY

3962

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

Load Supply Voltage Range VBB Operating, I OUT = ±800 mA, L = 3 mH 5.0 — 30 V

Output Sustaining Voltage VCE(sus) IOUT = ±800 mA, L = 3 mH — — 30 +VFV

Output Leakage Current ICEX VOUT = VBB — <1.0 50 µA

VOUT = 0 V — <1.0 -50 µA

Output Saturation Voltage VCE(SAT) Source Driver, IOUT = -500 mA — 1.0 1.2 V

Source Driver, IOUT = -750 mA — 1.1 1.5 V

Source Driver, IOUT = -800 mA — — 1.7 V

Sink Driver, IOUT = +500 mA — 0.3 0.6 V

Sink Driver, IOUT = +750 mA — 0.5 1.2 V

Sink Driver, IOUT = +800 mA — — 1.5 V

Clamp Diode Forward Voltage VFIF = 500 mA — 1.1 1.4 V

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

IF = 800 mA — — 1.7 V

Motor Supply Current IBB(ON) VENABLE = 0.8 V — 5.0 7.0 mA

(No Load) IBB(OFF) VENABLE = 2.4 V — 5.0 7.0 mA

ELECTRICAL CHARACTERISTICS at TA = +25°C, VBB = 30 V, VCC = 4.75 V to 5.25 V, VSENSE = 0

V, 30 kΩ & 1000 pF RC to Ground (unless noted otherwise)

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Output Drivers

Continued next page…

Logic Supply Voltage Range VCC Operating 4.75 — 5.25 V

Logic Input Voltage VIN(1) 2.4 — — V

VIN(0) — — 0.8 V

Logic Input Current IIN(1) VIN = 2.4 V — <1.0 20 µA

IIN(0) VIN = 0.8 V — <-2.0 -200 µA

Control Logic

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

3962

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

Reference Output Voltage VREF OUT VCC = 5.0 V, IREF OUT = 90 to 900 µA 2.45 2.50 2.55 V

Reference Output Current IREF OUT 3 kΩ ≤ RD = R1 + R2 ≤ 15 kΩ150 — 900 µA

Ref. Input Offset Current IOS VREF IN = 1 V -2.5 0 1.0 µA

Comparator Input Offset Volt. VIO VREF = 0 V -6.0 0 6.0 mV

Comparator Input Volt. Range VREF Operating -0.3 — 1.0 V

PWM RC Fixed Off-time tOFF RC CT = 1000 pF, RT = 30 kΩ27 30 33 µs

PWM Propagation Delay Time tPWM Comparator Trip to Source OFF — 1.2 2.0 µs

PWM Minimum On Time tON (min) CT = 1000 pF ± 5%, RT ≥ 15 kΩ, VCC = 5 V — 2.5 3.6 µs

Propagation Delay Times tpd IOUT = ±800 mA, 50% to 90%:

ENABLE ON to Source ON — 3.2 — µs

ENABLE OFF to Source OFF — 1.2 — µs

ENABLE ON to Sink ON — 3.2 — µs

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. TJ— 165 — °C

Thermal Shutdown Hysteresis ∆TJ—15—°C

UVLO Disable Threshold 2.5 2.7 2.9 V

UVLO Hysteresis 0.7 0.9 1.1 V

Logic Supply Current ICC(ON) VENABLE1 = VENABLE2 = 0.8 V — 60 85 mA

ICC(OFF) VENABLE1 = VENABLE2 = 2.4 V — 11 17 mA

Logic Supply Current ∆ICC(ON) VENABLE 1 = VENABLE 2 = 0.8 V — 0.18 — mA/°C

Temperature Coefficient

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

ELECTRICAL CHARACTERISTICS at TA = +25°C, VBB = 30 V, VCC = 4.75 V to 5.25 V, VSENSE = 0

V, 30 kΩ & 1000 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.

3962

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

FUNCTIONAL DESCRIPTION

Internal PWM Current Control. The A3962SLB 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 peak value of the current limiting

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

resistor (RS) and reference input voltage (VREF IN). The

internal circuitry compares the voltage across the external

sense resistor to the voltage on the reference input

terminal (VREF IN) resulting in a transconductance function

approximated by:

The reference input voltage is typically set with a

resistor divider from VREF OUT. To ensure proper operation

of the 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 ITRIP, the

comparator resets a latch that turns off the selected source

driver. The load inductance causes the current to recircu-

late 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

(tOFF = RTCT) during which the source driver remains

disabled (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 off-time

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

internal current-control circuitry (or by the PHASE or

ENABLE inputs). The comparator output is blanked to

prevent false over-current detections due to reverse-

recovery 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 tOFF

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, CT

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

sufficient 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 tOFF. For more

information 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

user-selected value of tOFF and the minimum on-time pulse

tON(min)max that occurs each time the PWM latch is reset.

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:

VREF IN

ITRIP ≈

[(VBB - VSAT(SOURCE+SINK)) tON(min)max] – (1.05 (VSAT(SINK) + VF) tOFF)

1.05 (tON(min)max + tOFF) RLOAD

I AVG ≈

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

3962

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

dc servo motor applications as the transfer function

between 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 hyster-

esis of the thermal shutdown circuit is approximately 15°C.

APPLICATION NOTES

Current Sensing. The actual peak load current (IPEAK) will

be above the calculated value of ITRIP due to delays in the

turn off of the drivers. The amount of overshoot can be

approximated by:

where VBB is the motor supply voltage, VBEMF is the back-

EMF voltage of the load, RLOAD and LLOAD are the resis-

tance and inductance of the load respectively, and t PWM is

specified in the electrical characteristics table.

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 aforemen-

tioned effects but can result in excessive heating and

power loss in the sense resistor. The selected value of RS

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:

where tOFF = RTCT, RLOAD is the series resistance of the

load, VBB is the motor supply voltage and t 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 VREF to 0 volts. With the load connected and 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 (tON(min)typ) for the device. The

CT then should be increased until the measured value of

tON(min) is equal to tON(min)max as specified in the electrical

characteristics table. When the new value of CT has been

set, the value of RT should be decreased so the value for

tOFF = RTCT (with the artificially increased value of CT)

is equal to the nominal design value. The worst-case load-

current 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 corre-

sponding 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

(VBB – [(ITRIP • RLOAD) + VBEMF]) tPWM

LLOAD

IOS ≈

0.5

ITRIPmax ± 50%

RS ≈

3962

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 indepen-

dent from the high-current power-ground trace to avoid

changes in REFIN due to I•R 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, TTAB . The junction temperature can then be

approximated by using the formula:

TJ ≈ TTAB + (ILOAD 2 VF RθJT)

where VF can be chosen from the electrical specification

table for the given level of ILOAD. The value for RθJT 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 I•R 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 Consider-

ations” above.

Fixed Off-Time Selection. With increasing values of tOFF,

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 tOFF can be chosen for optimization of these

parameters. For applications where audible noise is a

concern, typical values of tOFF are chosen to be in the

range of 15 to 35 ms.

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

3962

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

Dimensions in Inches

(for reference only)

Dimensions in Millimeters

(controlling dimensions)

0°

8°

1 2 3

0.020

0.013

0.0040

MIN.

0.0125

0.0091

0.050

0.016

wg. MA-008-21A in

0.050

BSC

20 11

NOTE 1

NOTE 3

0.2992

0.2914 0.419

0.394

0.5118

0.4961

0.0926

0.1043

0°

8°

0.51

0.33

0.10

MIN.

Dwg. MA-008-21A mm

1.27

BSC

11 0.32

0.23

1.27

0.40

NOTE 1

NOTE 3

7.60

7.40 10.65

10.00

13.00

12.60

2.65

2.35

NOTES: 1. Webbed lead frame. Leads 5, 6, 15, and 16 are internally one piece.

2. Lead spacing tolerance is non-cumulative.

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

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.