Data Sheet
29319.44
The A3957SA and A3957SLB 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 combined with an internal
four-bit nonlinear digital-to-analog converter allows the motor current to be
controlled in full-, half-, quarter-, eighth-, or sixteenth-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 hysteresis,
transient-suppression diodes, and crossover current protection. Special
power-up sequencing is not required.
The A3957S-- is supplied in a choice of two power packages; a 16-pin
dual-in-line plastic package (suffix `A'), and a 24-lead plastic SOIC with
copper heat-sink tabs (suffix `LB'). The power tab is at ground potential and
needs no electrical isolation.
FEATURES
s
1.5 A Continuous Output Current
s 50 V Output Voltage Rating
s Internal PWM Current Control
s 4-Bit Non-Linear DAC for 16-Bit Microstepping
s SatlingtonTM Sink Drivers
s Fast, Mixed Fast/Slow, and Slow Current-Decay Modes
s Internal Transient-Suppression Diodes
s Internal Thermal-Shutdown Circuitry
s Crossover-Current and UVLO Protection
FULL-BRIDGE PWM
MICROSTEPPING MOTOR DRIVER
3957
Always order by complete part number:
Part Number
Package
R
JA
R
JC
R
JT
A3957SA
16-pin DIP
60
C/W
38
C/W
--
A3957SLB
24-lead batwing SOIC
56
C/W
--
6
C/W
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 (T
A
= 25
C), P
D
A3957SA . . . . . . . . . . . . . . . . 2.08 W
A3957SLB . . . . . . . . . . . . . . . 2.23 W
Operating Temperature Range,
T
A
. . . . . . . . . . . . . . . -20C to +85C
Junction Temperature, T
J
. . . . . . . . +150C
Storage Temperature Range,
T
S
. . . . . . . . . . . . . . . -55C to +150C
* 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.
Per SEMI G42-88 Specification, Thermal Test
Board Standardization for Measuring Junction-
to-Ambient Thermal Resistance of Semiconductor
Packages..
GROUND
GROUND
LOGIC
SUPPLY
PHASE
GROUND
GROUND
RC
SENSE
D
Dwg. PP-056-4
REF
LOAD
SUPPLY
V
CC
OUTB
OUTA
V
BB
LOGIC
PFD
1
D 0
D 2
1
2
3
22
23
24
6
7
18
19
4
5
21
20
8
9
10
15
16
17
11
12
14
13
NO
CONNECT
NO
CONNECT
NO
CONNECT
D 3
NO
CONNECT
NO
CONNECT
NO
CONNECT
NO
CONNECT
NC
NC
NC
NC
NC
NC
NC
A3957SLB
3957
FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
13
REF
D
3
11
20
D/A
2
1
0
PFD
2
+
V
BB
RC
R S
Dwg. FP-042-1
SENSE
17
18
19
V
CC
BLANKING
V
CC
LOGIC
SUPPLY
9
PHASE
10
UVLO
& TSD
GROUND
Q
R
S
PWM LATCH
+
VTH
R T
C T
5
6
LOAD
SUPPLY
23
7
MIXED-DECAY
COMPARATOR
+
OUT
A
OUT
B
15
22
3
DISABLE
CURRENT-SENSE
COMPARATOR
BLANKING
GATE
D
D
D
8
3
FUNCTIONAL BLOCK DIAGRAM (A3957SLB shown)
W
Copyright 1998 Allegro MicroSystems, Inc.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
LOGIC
SUPPLY
PHASE
GROUND
RC
SENSE
D 3
Dwg. PP-056-3
REF
LOAD
SUPPLY
V
CC
OUTB
OUTA
V
BB
PFD
D 1
D 0
GROUND
D 2
NO
CONNECT
NC
LOGIC
A3957SA
For the `A' package, pins 1 and 8 must
be externally connected together.
3957
FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
ELECTRICAL CHARACTERISTICS at T
A
= 25C, V
BB
= 5 V to 50 V, V
CC
= 4.5 V to 5.5 V (unless
otherwise noted.)
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Power Outputs
Load Supply Voltage Range
V
BB
Operating, I
OUT
=
1.5 A, L = 3 mH
V
CC
--
50
V
Output Leakage Current
I
CEX
V
OUT
= V
BB
--
<1.0
50
A
V
OUT
= 0 V
--
<-1.0
-50
A
Output Saturation Voltage
V
CE(SAT)
V
S
= 1.0 V:
(Forward or Reverse Mode)
Source Driver, I
OUT
= -0.85 A
--
1.1
1.2
V
Source Driver, I
OUT
= -1.5 A
--
1.4
1.5
V
Sink Driver, I
OUT
= 0.85 A
--
0.5
0.7
V
Sink Driver, I
OUT
= 1.5 A
--
1.2
1.5
V
Sense Current Offset
I
SO
I
S
- I
OUT
, I
OUT
= 850 mA,
20
30
40
mA
V
S
= 0 V, V
CC
= 5 V
Clamp Diode Forward Volt.
V
F
I
F
= 0.85 A
--
1.2
1.4
V
(Sink or Source)
I
F
= 1.5 A
--
1.5
1.7
V
Motor Supply Current
I
BB(ON)
--
2.0
4.0
mA
(No Load)
I
BB(OFF)
D
0
= D
1
= D
2
= D
3
= 0.8 V
--
1.0
50
A
Control Circuitry
Logic Supply Voltage Range
V
CC
Operating
4.5
5.0
5.5
V
Reference Voltage Range
V
REF
Operating
0.5
--
2.5
V
UVLO Enable Threshold
V
CC
= 0
5 V
3.35
3.70
4.05
V
UVLO Hysteresis
0.25
0.40
0.55
V
Logic Supply Current
I
CC(ON)
--
42
50
mA
I
CC(OFF)
D
0
= D
1
= D
2
= D
3
= 0.8 V
--
14
17
mA
Logic Input Voltage
V
IN(1)
2.0
--
--
V
V
IN(0)
--
--
0.8
V
Logic Input Current
I
IN(1)
V
IN
= 2.0 V
--
<1.0
20
A
I
IN(0)
V
IN
= 0.8 V
--
<-2.0
-200
A
Continued next page...
PDF 
ZIP
