3955
FULL-BRIDGE PWM
MICROSTEPPING MOTOR DRIVER
PFD
REF
RC
GROUND
GROUND
LOGIC
SUPPLY
PHASE
D2
1
2
3
4
LOGIC
5
6
7
8
V
CC
12
11
10
9
GROUND
SENSE
OUTA
D1
V
BB
16
15
14
13
LOAD
SUPPLY
OUTB
D0
GROUND
Data Sheet
29319.41
The A3955SB and A3955SLB are designed for driving one winding
of a bipolar stepper motor in a microstepping mode. The outputs are
rated for continuous output currents to
±1.5
A and operating voltages
to 50 V. Internal pulse-width modulated (PWM) current control com-
bined with an internal three-bit nonlinear digital-to-analog converter
allows the motor current to be controlled in full-, half-, quarter-, or
eighth-step (microstepping) modes. Nonlinear increments minimize
the number of control lines necessary for microstepping.
Microstepping provides for increased step resolution, and reduces
torque variations and resonance problems at low speed.
Internal circuitry determines whether the PWM current-control
circuitry operates in a slow (recirculating) current-decay mode, fast
(regenerative) current-decay mode, or in a mixed current-decay mode
in which the off time is divided into a period of fast current decay with
the remainder of the fixed off time spent in slow current decay. The
combination of user-selectable current-sensing resistor and reference
voltage, digitally selected output current ratio; and slow, fast, or mixed
current-decay modes provides users with a broad, variable range of
motor control.
Internal circuit protection includes thermal shutdown with hyster-
esis, transient-suppression diodes, and crossover current protection.
Special power-up sequencing is not required.
The A3955S— is supplied in a choice of two power packages; a
16-pin dual-in-line plastic package with copper heat-sink tabs (suffix
‘B’), and a 16-lead plastic SOIC with copper heat-sink tabs (suffix ‘LB’).
For both package styles, the power tab is at ground potential and
needs no electrical isolation.
Dwg. PP-056-2
Note the A3955SB (DIP) and the A3955SLB
(SOIC) are electrically identical and share a
common terminal number assignment.
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage, V
BB
. . . . . . . . . .
50 V
Output Current, I
OUT
(Continuous) . . . . . . . . . . . . . .
±
1.5 A*
Logic Supply Voltage, V
CC
. . . . . . . . .
7.0 V
Logic/Reference Input Voltage Range,
V
IN
. . . . . . . . . . .
-0.3 V to V
CC
+ 0.3 V
Sense Voltage, V
S
. . . . . . . . . . . . . . . .
1.0 V
Package Power Dissipation,
P
D
. . . . . . . . . . . . . . . . . . . .
See Graph
Operating Temperature Range,
T
A
. . . . . . . . . . . . . . . . .
-20˚C to +85˚C
Junction Temperature, T
J
. . . . . . .
+150˚C†
Storage Temperature Range,
T
S
. . . . . . . . . . . . . . . .
-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 temperature
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.
FEATURES
s
s
s
s
s
s
s
s
±1.5
A Continuous Output Current
50 V Output Voltage Rating
Internal PWM Current Control
3-Bit Non-Linear DAC
Fast, Mixed Fast/Slow, and Slow Current-Decay Modes
Internal Transient-Suppression Diodes
Internal Thermal-Shutdown Circuitry
Crossover-Current and UVLO Protection
Always order by complete part number:
Part Number
A3955SB
A3955SLB
Package
16-Pin DIP
16-Lead SOIC
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
