A3968
Dual Full-Bridge PWM Motor Driver
Features and Benefits
▪
±650 mA continuous output current
▪
30 V output voltage rating
▪
Internal fixed-frequency PWM current control
▪
Satlington® sink drivers
▪
Brake mode
▪
User-selectable blanking window
▪
Internal ground-clamp and flyback diodes
▪
Internal thermal-shutdown circuitry
▪
Crossover-current protection and UVLO protection
Description
The A3968 bidirectionally controls two DC motors. The device
includes two full-bridges capable of continuous output currents
of ±650 mA and operating voltages to 30 V. Motor winding
current can be controlled by the internal fixed-frequency,
pulse-width modulated (PWM), current-control circuitry. The
peak load current limit is set by user selection of a reference
voltage and current-sensing resistors.
The fixed-frequency pulse duration is set by a user-selected
external RC timing network. 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.
To reduce on-chip power dissipation, the full-bridge power
outputs have been optimized for low saturation voltages. The
sink drivers feature the Allegro
™
patented Satlington
®
output
structure. The Satlington outputs combine the low voltage drop
of a saturated transistor and the high peak current capability
of a Darlington.
For each bridge, the INPUT
A
and INPUT
B
terminals determine
the load-current polarity by enabling the appropriate source and
sink driver pair. When a logic low is applied to both INPUTs
Package: 16 pin SOIC (suffix LB)
Not to scale
Continued on the next page…
Typical Application
MOTOR
1
1
INPUT
1A
INPUT
1B
V
2
3
4
0.5
Ω
5
+5 V
6
39 kΩ
BB
MOTOR
2
16
15
14
LOGIC
LOGIC
13
0.5
Ω
12
11
V
7
8
10 kΩ
BB
INPUT
2A
INPUT
2B
+24 V
V
CC
10
9
56 kΩ
+5 V
680 pF
V
REF
RC
47
μF
+
Dwg. EP-047-6
29319.29G
A3968
Description (continued)
Dual Full-Bridge PWM Motor Driver with Brake
of a bridge, the braking function is enabled. In brake mode, both
source drivers are turned off and both sink drivers are turned on,
thereby dynamically braking the motor. When a logic high is applied
to both INPUTs of a bridge, all output drivers are disabled.
Special power-up sequencing is not required. Internal circuit
protection includes thermal shutdown with hysteresis, ground-clamp
and flyback diodes, and crossover-current protection.
The A3968 is supplied in a 16-lead plastic SOIC with two pins
internally fused to the die pad for enhanced thermal dissipation. These
pins are at ground potential and need no electrical isolation. The
device is lead (Pb) free, with 100% matte tin leadframe plating.
Selection Guide
Part Number
A3968SLBTR–T
Packing
1000 pieces / reel
Ambient Temperature Range
(°C)
–20 to 85
Absolute Maximum Ratings
Characteristic
Load Supply Voltage
Logic Supply Voltage
Input Voltage
Sense Voltage
Symbol
V
BB
V
CC
V
IN
V
S
Peak
Output Current*
I
OUT
Continuous
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 T
J
(max)
Notes
Rating
30
7.0
–0.3 to V
CC
+ 0.3
1.0
±750
±650
Units
V
V
V
V
mA
mA
Package Power Dissipation
P
D
T
A
= 25°C; per SEMI G42-88 Specification, Thermal Test
Board Standardization for Measuring Junction-to-Ambient
Thermal Resistance of Semiconductor Packages.
Range E
Range S
1.8
–40 to 85
–20 to 85
150
–55 to 150
W
ºC
ºC
ºC
ºC
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
T
A
T
J
(max)
T
stg
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
A3968
Dual Full-Bridge PWM Motor Driver with Brake
FUNCTIONAL BLOCK DIAGRAM
(One Half of Circuit Shown)
LOGIC
SUPPLY
LOAD
SUPPLY
OUTA
OUTB
INPUTA
V CC
+
V BB
UVLO
& TSD
INPUTB
SOURCE
ENABLE
BLANKING
GATE
CURRENT-SENSE
COMPARATOR
CONTROL LOGIC
SENSE
TO OTHER
BRIDGE
÷4
PWM LATCH
R
Q
S
+
–
TO OTHER
BRIDGE
GROUND
RC
OSC
TO OTHER
BRIDGE
RS
RT
CT
REFERENCE
Dwg. FP-036-4
TRUTH TABLE
INPUT
A
L
L
H
H
INPUT
B
L
H
L
H
OUT
A
L
L
H
Z
OUT
B
L
H
L
Z
Description
Brake mode
“Forward”
“Reverse”
Disable
Z = High impedance
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
A3968
Dual Full-Bridge PWM Motor Driver with Brake
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
BB
= 30 V, V
CC
= 4.75 V to 5.5 V, V
REF
= 2 V,
V
S
= 0 V, 56 k
Ω
& 680 pF RC to Ground (unless noted otherwise)
Limits
Characteristic
Output Drivers
Load Supply Voltage Range
Output Leakage Current
V
BB
I
CEX
Operating, I
OUT
=
±650
mA, L = 3 mH
V
OUT
= 30 V
V
OUT
= 0 V
Output Saturation Voltage
V
CE(SAT)
Source Driver, I
OUT
= -400 mA
Source Driver, I
OUT
= -650 mA
Sink Driver, I
OUT
= +400 mA, V
S
= 0.5 V
Sink Driver, I
OUT
= +650 mA, V
S
= 0.5 V
Clamp Diode Forward Voltage
V
F
I
F
= 400 mA
I
F
= 650 mA
Motor Supply Current
(No Load)
I
BB(ON)
I
BB(OFF)
Both bridges ON (forward or reverse)
All INPUTs = 2.4 V
V
CC
—
—
—
—
—
—
—
—
—
—
—
<1.0
<-1.0
1.7
1.8
0.3
0.7
1.1
1.4
3.0
<1.0
30
50
-50
2.0
2.1
0.5
1.3
1.4
1.6
5.0
200
V
μA
μA
V
V
V
V
V
V
mA
μA
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Control Logic
Logic Supply Voltage Range
Logic Input Voltage
V
CC
V
IN(1)
V
IN(0)
Logic Input Current
I
IN(1)
I
IN(0)
Reference Input Volt. Range
Reference Input Current
Reference Divider Ratio
Current-Sense Comparator
Input Offset Voltage
Current-Sense Comparator
Input Voltage Range
Sense-Current Offset
V
REF
I
REF
V
REF
/V
TRIP
V
IO
V
S
I
SO
V
REF
= 0.1 V
Operating
I
S
– I
OUT
, 50 mA
≤
I
OUT
≤
650 mA
V
IN
= 2.4 V
V
IN
= 0.8 V
Operating
Operating
4.75
2.4
—
—
—
0.1
-2.5
3.8
-6.0
-0.3
12
—
—
—
<1.0
<-20
–
0
4.0
0
—
18
5.50
—
0.8
20
-200
2.0
1.0
4.2
6.0
1.0
24
V
V
V
μA
μA
V
μA
—
mV
V
mA
NOTES:1. Typical Data is for design information only.
2. Negative current is defined as coming out of (sourcing) the specified device terminal.
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
A3968
Dual Full-Bridge PWM Motor Driver with Brake
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
BB
= 30 V, V
CC
= 4.75 V to 5.5 V, V
REF
= 2 V,
V
S
= 0 V, 56 k
Ω
& 680 pF RC to Ground (unless noted otherwise) (cont.)
Limits
Characteristic
Control Logic
(continued)
PWM RC Frequency
PWM Propagation Delay Time
f
osc
t
PWM
C
T
= 680 pF, R
T
= 56 kΩ
Comparator Trip to Source OFF
Cycle Reset to Source ON
Cross-Over Dead Time
Propagation Delay Times
t
codt
t
pd
1 kΩ Load to 25 V
I
OUT
=
±650
mA, 50% to 90%:
Disable OFF to Source ON
Disable ON to Source OFF
Disable OFF to Sink ON
Disable ON to Sink OFF
Brake Enable to Sink ON
Brake Enable to Source OFF
22.9
—
—
0.2
—
—
—
—
—
—
—
—
Increasing V
CC
Both bridges ON (forward or reverse)
All INPUTs = 2.4 V
All INPUTs = 0.8 V
—
0.1
—
—
—
25.4
1.0
0.8
1.8
100
500
200
200
2200
200
165
15
4.1
0.6
—
—
—
27.9
1.4
1.2
3.0
—
—
—
—
—
—
—
—
4.6
—
50
9.0
95
kHz
μs
μs
μs
ns
ns
ns
ns
ns
ns
°C
°C
V
V
mA
mA
mA
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Thermal Shutdown Temp.
Thermal Shutdown Hysteresis
UVLO Enable Threshold
UVLO Hysteresis
Logic Supply Current
T
J
ΔT
J
V
T(UVLO)+
V
T(UVLO)hys
I
CC(ON)
I
CC(OFF)
I
CC(BRAKE)
NOTES:1. Typical Data is for design information only.
2. Negative current is defined as coming out of (sourcing) the specified device terminal.
2.5
T
A
= +25°C
2.0
SOURCE DRIVER
1.5
OUTPUT SATURATION VOLTAGE IN VOLTS
1.0
0.5
SINK DRIVER
0
Typical output saturation voltages showing
Satlington sink-driver operation.
200
300
400
500
600
7 00
OUTPUT CURRENT IN MILLIAMPERES
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
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