3968
ADVANCE INFORMATION
(subject to change without notice)
September 3, 1999
DUAL FULL-BRIDGE PWM
MOTOR DRIVER WITH BRAKE
The A3968SA and A3968SLB are designed to bidirectionally control two
dc motors. Each device includes two H-bridges capable of continuous output
currents of
鹵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 the
user鈥檚 selection of a reference voltage and current-sensing resistors. Except
for package style and pinout, the two devices are identical.
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 H-bridge power outputs have
been optimized for low saturation voltages. The sink drivers feature Allegro鈥檚
patented Satlington鈩?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 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 A3968SA is supplied in a 16-pin dual in-line plastic package. The
A3968SLB is supplied in a 16-lead plastic SOIC with copper heat sink tabs.
The power tab is at ground potential and needs no electrical isolation.
Data Sheet
29319.29
A3968SLB
OUT
1A
INPUT
1A
INPUT
1B
GROUND
SENSE
1
OUT
1B
LOAD
SUPPLY
REFERENCE
1
V
2
3
4
5
6
V
7
8
V
BB
BB
16
15
14
LOGIC
LOGIC
13
12
11
V
CC
RC
10
9
OUT
2A
INPUT
2A
INPUT
2B
GROUND
SENSE
2
OUT
2B
LOGIC
SUPPLY
RC
REF
Dwg. PP-066
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage, V
BB
...................
30 V
Output Current, I
OUT
(peak) ..........
鹵
750 mA
(continuous) ..............................
鹵
650 mA
Logic Supply Voltage, V
CC
.................
7.0 V
Input Voltage, V
in
.....
-0.3 V to V
CC
+ 0.3 V
Sense Voltage, V
S
................................
1.0 V
Package Power Dissipation (T
A
= 25擄C), P
D
A3968SA ...................................
2.08 W*
A3968SLB .................................
1.87 W*
Operating Temperature Range,
T
A
...................................
-20
擄
C to +85
擄
C
Junction Temperature,
T
J
.................................................
+150
擄
C
Storage Temperature Range,
T
S
.................................
-55
擄
C to +150
擄
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 temperature
of 150擄C.
* Per SEMI G42-88 Specification,
Thermal Test
Board Standardization for Measuring Junction-
to-Ambient Thermal Resistance of Semiconductor
Packages.
FEATURES
s
s
s
s
s
s
s
s
s
鹵650
mA Continuous Output Current
30 V Output Voltage Rating
Internal Fixed-Frequency PWM Current Control
Satlington鈩?Sink Drivers
Brake Mode
User-Selectable Blanking Window
Internal Ground-Clamp & Flyback Diodes
Internal Thermal-Shutdown Circuitry
Crossover-Current Protection and UVLO Protection
Always order by complete part number:
Part Number
A3968SA
A3968SLB
Package
16-pin DIP
16-lead batwing SOIC
R
胃JA
60擄C/W
67擄C/W
R
胃JC
38擄C/W
1
2
3
4
5
6
7
8
9
10
11
12
