2927
DUAL FULL-BRIDGE
PWM MOTOR DRIVER

DISCONTINUED PRODUCT

-- FOR REFERENCE ONL

GND

Dwg. PP-021

PWM 1

PWM 2

LOGIC SUPPLY

OUT

SENSE

REF 1

PHASE

ENABLE

OUT

LOAD SUPPLY

OUT

SENSE

REF 2

PHASE

ENABLE

OUT

The A2927SEB motor driver is designed to drive both windings of a

bipolar stepper motor or bidirectionally control two dc motors. Both
bridges are capable of sustaining 50 V and include internal pulse-width
modulation (PWM) control of the output current to 1.5 A.

For PWM current control, the maximum output current is determined

by the user's selection of a reference voltage and sensing resistor. Two
logic-level inputs select output current limits of 0, 33%, 67%, or 100%
of the maximum level. A PHASE input to each bridge determines load
current direction. Active-low ENABLE inputs control the four drivers in
each bridge.

Internally generated delays prevent cross-over currents when

switching current direction. Special power-up sequencing is not required.
Thermal protection circuitry disables the outputs if the chip temperature
exceeds safe operating limits.

The A2927SEB is supplied in a 44-lead power PLCC for surface-

mount applications. Its batwing construction provides for maximum
package power dissipation in the smallest possible construction.

DUAL FULL-BRIDGE

PWM MOTOR DRIVER

Always order by complete part number: A2927SEB .

FEATURES

1.5 A Output Current

50 V Output Sustaining Voltage

Internal Flyback Diodes

Digital Control of Output Current

Undervoltage Lockout

Internal Thermal Shutdown Circuitry

Data Sheet

29319.23

2927

PRELIMINARY INFORMATION

(Subject to change without notice)

September 16, 1997

ABSOLUTE MAXIMUM RATINGS

at T

+150

�

Motor Supply Voltage, V

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

Output Current, I

OUT

.........................

�

1.5 A

Logic Supply Voltage, V

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

Logic Input Voltage Range,

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

Output Emitter Voltage, V

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

Package Power Dissipation,

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

Operating Temperature Range,

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

�

C to +85

�

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 peak
current rating or a junction temperature of +150

�

2927
DUAL FULL-BRIDGE
PWM MOTOR DRIVER

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

PWM CURRENT-CONTROL CIRCUITRY

TRUTH TABLE

Enable

Phase

Out

X = Don't care
Z = High impedance

REF

OUTA

OUT

Dwg. EP-007-4

SENSE

ONE

SHOT

SOURCE
DISABLE

�
+

�

CHANNEL 1
PIN NUMBERS
SHOWN.

20 k

40 k

10 k

100

125

150

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

TEMPERATURE IN

�

Dwg. GP-020-1

12.5

2.5

7.5

5.0

R = 6

�

C/W

R = 35

�

C/W

2927
DUAL FULL-BRIDGE
PWM MOTOR DRIVER

ELECTRICAL CHARACTERISTICS at T

= +25

�

C, V

= 50 V, V

= 5.0 V, V

REF

= 5.0 V (unless

otherwise noted).

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Output Drivers (OUT

or OUT

)

Motor Supply Range

OUT

�

1.5 A, L = 15 mH

Output Leakage Current

CEX

OUT

= V

<1.0

5.0

�

OUT

= 0

<-1.0

-5.0

�

Output Saturation Voltage

CE(SAT

)

Sink Driver, I

OUT

= +1.0 A*

0.5

0.7

Sink Driver, I

OUT

= +1.5 A*

0.8

0.9

Source Driver, I

OUT

= -1.0 A*

1.8

1.9

Source Driver, I

OUT

= -1.5 A*

1.9

2.0

Flyback Diode Forward Volt.

= 1.5 A

1.6

2.0

Driver Supply Current

BB(ON)

Both Bridges ON, No Load

6.5

9.0

BB(OFF)

Both Bridges OFF

4.0

Control Logic

Input Voltage

IN(1)

All Inputs

2.4

IN(0)

All Inputs

0.8

Input Current

IN(1)

= 2.4 V

<1.0

�

IN(0)

= 0.8 V

-3.0

-200

�

Reference Voltage Range

REF

Operating

1.5

7.5

Current Limit Threshold

REF

SENSE

= I

= 0.8 V

9.5

10.5

= 2.4 V, I

= 0.8 V

13.5

16.5

= 0.8 V, I

= 2.4 V

25.5

34.5

Thermal Shutdown Temp.

170

�

Total Logic Supply Current

CC(ON)

= I

= V

= 0.8 V, No Load

105

CC(OFF)

= I

= 2.4 V, No Load

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

Typical Data is for design information only.

* Pulse test (<10 ms).

Limits

(at trip point)

2927
DUAL FULL-BRIDGE
PWM MOTOR DRIVER

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

APPLICATIONS INFORMATION

PWM CURRENT CONTROL:

The UDN2927EB dual bridge is designed

to drive both windings of a bipolar stepper
motor. Output current is sensed and con-
trolled independently in each bridge by an
external sense resistor (R

), internal com-

parator, and monostable multivibrator.

When the bridge is turned ON, current

increases in the motor winding and it is
sensed by the external sense resistor until
the sense voltage (V

SENSE

) reaches the level

set at the comparator's input:

TRIP

= V

REF

/10 R

The comparator then triggers the mon-

ostable which turns OFF the source driver of
the bridge. The actual load current peak will
be slightly higher than the trip point (espe-
cially for low-inductance loads) because of
the internal logic and switching delays. This
delay (t

) is typically 2

�

s. After turn-off, the

motor current will normally decay, circulating
through the external ground clamp diode and
sink transistor. The source driver's OFF time
(and therefore the magnitude of the current
decrease) is determined by the monostable's
external RC timing components, where t

off

within the range of 20 k

to 100 k

and 200 pF to 500 pF.

When the source driver is re-enabled, the

winding current (the sense voltage) is again
allowed to rise to the comparator's threshold.
This cycle repeats itself, maintaining the
average motor winding current at the desired
level.

Special circuitry has been included to

prevent runaway current control when the
fixed OFF time (t

off

) is set too short. This

circuitry prevents the source driver from
being re-enabled until the load current has
decayed to below the I

TRIP

level.

PWM OUTPUT CURRENT WAVEFORM

�

PHASE

OUT

off

TRIP

Dwg. WM-003-1A

LOAD CURRENT PATHS

Dwg. EP-006-14

R S

BRIDGE ON
SOURCE OFF
ALL OFF

2927
DUAL FULL-BRIDGE
PWM MOTOR DRIVER

CURRENT-CONTROL

TRUTH TABLE

Loads with high distributed capacitances may result in

high turn-ON current peaks. This peak (appearing across
R

) will attempt to trip the comparator, resulting in errone-

ous current control or high-frequency oscillations. An
external R

low-pass filter may be needed to delay the

action of the comparator.

LOGIC CONTROL OF OUTPUT CURRENT:

Two logic level inputs (I

and I

) allow digital selection

of the motor winding current at 100%, 67%, 33%, or 0% of
the maximum level per the table. The 0% output current
condition turns OFF all drivers in the bridge and can be
used as an output enable function. These logic level
inputs greatly enhance the implementation of

�

P-con-

trolled drive formats.

During half-step operations, the I

and I

inputs allow

the

�

P to control the motor at a constant torque between

all positions in an eight-step sequence. This is accom-
plished by digitally selecting 100% drive current when only
one phase is ON and 67% drive current when two phases
are ON.

The logic control inputs can also be used to select a

reduced current level (and reduced power dissipation) for
`hold' conditions and/or increased current (and available
torque) for start-up conditions.

GENERAL:

Both bridges have internal flyback diodes (connected

from the outputs to V

) for protection against inductive

transients. External ground-clamp diodes (connected
from the outputs to ground) are required; Schottky
ground-clamp diodes are recommended to minimize on-
chip power dissipation.

To avoid excessive voltage spikes on the LOAD

SUPPLY terminal (V

), a large-value capacitor (

�

should be connected from V

to ground as close as

possible to the device. Under no circumstances should
the voltage at LOAD SUPPLY exceed 50 V. A low-value
(0.1

�

F) ceramic capacitor at this terminal may be used

for high-frequency noise suppression.

The PHASE input to each bridge determines the

direction motor winding current flows. An internally
generated deadtime (approximately 3

�

s) prevents

crossover currents that can occur when switching the
PHASE input.

All four drivers in the bridge output can be turned OFF

2.4 V or I

= I

2.4 V), resulting in a fast current

decay through the internal flyback and external ground-
clamp diodes. The fast current decay is desirable in half-
step and high-speed applications. All logic inputs float
high; the ENABLE input must be tied low if it is not used.

Varying the reference voltage (V

REF

) provides continu-

ous control of the peak load current for micro-stepping
applications, within the specified limits for V

REF

Thermal protection circuitry turns OFF all drivers

when the junction temperature reaches approximately
+170

�

C. It is only intended to protect the device from

failures due to excessive junction temperature and should
not imply that output short circuits are permitted. The
output drivers are reenabled when the junction tempera-
ture cools to approximately +160

�

Output Current

REF

/10 R

= I

TRIP

REF

/15 R

2/3 I

TRIP

REF

/30 R

= 1/3 I

TRIP

Электронный компонент: A2927SEB