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3957 Schematic ( PDF Datasheet ) - Allegro MicroSystems

Teilenummer 3957
Beschreibung FULL-BRIDGE PWM MICROSTEPPING MOTOR DRIVER
Hersteller Allegro MicroSystems
Logo Allegro MicroSystems Logo 




Gesamt 16 Seiten
3957 Datasheet, Funktion
3957
A3957SLB
NO 1 NC
CONNECT
PFD 2
VBB
REF 3
NO 4 NC
CONNECT
RC 5
GROUND 6
GROUND 7
LOGIC
D3 8
LOGIC
SUPPLY
9 VCC
PHASE 10
D 2 11
NO
CONNECT
12 NC
NC 24
23
NO
CONNECT
LOAD
SUPPLY
22 OUTB
NC 21
NO
CONNECT
20 D 0
19 GROUND
18 GROUND
17 SENSE
NC 16
NO
CONNECT
15 OUTA
NC 14
NO
CONNECT
13 D 1
Dwg. PP-056-4
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage, VBB . . . . . . . . . 50 V
Output Current, IOUT
(Continuous) . . . . . . . . . . . . . ±1.5 A*
Logic Supply Voltage, VCC . . . . . . . 7.0 V
Logic/Reference Input Voltage Range,
VIN . . . . . . . . . . -0.3 V to VCC + 0.3 V
Sense Voltage, VS . . . . . . . . . . . . . . . 1.0 V
Package Power Dissipation (TA = 25°C), PD
A3957SA . . . . . . . . . . . . . . . . 2.08 W
A3957SLB . . . . . . . . . . . . . . . 2.23 W
Operating Temperature Range,
TA . . . . . . . . . . . . . . . -20˚C to +85˚C
Junction Temperature, TJ . . . . . . . . +150˚C
Storage Temperature Range,
TS . . . . . . . . . . . . . . . -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.
† Per SEMI G42-88 Specification, Thermal Test
Board Standardization for Measuring Junction-
to-Ambient Thermal Resistance of Semiconductor
Packages..
FULL-BRIDGE PWM
MICROSTEPPING MOTOR DRIVER
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 Satlington™ 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
Always order by complete part number:
Part Number Package
A3957SA
16-pin DIP
A3957SLB
24-lead batwing SOIC
RθJA
60°C/W
56°C/W
RθJC
38°C/W
RθJT
6°C/W






3957 Datasheet, Funktion
3957
FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at TA = 25˚C, VBB = 5 V to 50 V, VCC = 4.5 V to 5.5 V (unless
otherwise noted.)
Characteristic
Symbol Test Conditions
Min.
Limits
Typ. Max.
Units
AC Timing
PWM RC Fixed Off-time
PWM Turn-Off Time
PWM Turn-On Time
PWM Minimum On Time
Crossover Dead Time
tOFF RC
tPWM(OFF)
tPWM(ON)
tON(min)
tCODT
CT = 470 pF, RT = 43 k
Current-Sense Comparator Trip
to Source OFF, IOUT = 100 mA
Current-Sense Comparator Trip
to Source OFF, IOUT = 1.5 A
IRC Charge ON to Source ON,
IOUT = 100 mA
IRC Charge ON to Source ON,
IOUT = 1.5 A
VCC = 5.0 V, RT 43 k, CT = 470 pF
IOUT = 100 mA
1 kLoad to 25 V
18.2
1.0
0.3
20.2
1.0
1.4
0.4
0.55
1.6
1.5
22.3
1.5
2.5
0.7
0.85
2.2
3.0
µs
µs
µs
µs
µs
µs
µs
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

6 Page









3957 pdf, datenblatt
3957
FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER
Thermal Considerations. Thermal-protection circuitry turns
off all output transistors when the junction temperature reaches
approximately +165°C. This is intended only to protect the
device from failures due to excessive junction temperatures and
should not imply that output short circuits are permitted. The
output transistors are re-enabled when the junction temperature
cools to approximately +150°C.
Stepper Motor Applications. The A3957SB or A3957SLB are
used to optimize performance in microstepping/sinusoidal
stepper-motor drive applications (see figures 4 and 5). When
the load current is increasing, the slow current-decay mode is
used to limit the switching losses in the driver and iron losses in
the motor. This also improves the maximum rate at which the
load current can increase (as compared to fast decay) due to the
slow rate of decay during tOFF. When the load current is
decreasing, the mixed current-decay mode is used to regulate
the load current to the desired level. This prevents tailing of the
current profile caused by the back-EMF voltage of the stepper
motor (see figure 3A).
V PFD
V REF
D3A
+5 V
PHASE A
D2A
BRIDGE A
1 NC
2
VBB
NC 24
VBB
23
3
4 NC
5
22
NC 21
20
47 µF
D 0A
6
LOGIC
7
19
181
8 17
9 VCC
10
NC 16
15
11 NC 14
12 NC
13 D1A
D 1B
D0B
47 µF
VBB
BRIDGE B
13
14 NC
15
16 NC
17
18
19
20
21 NC
22
23
24 NC
NC 12
11
10
VCC 9
8
LOGIC
7
6
5
NC 4
3
VBB 2
NC 1
Figure 4 — Typical Application
D2B
PHASE B
+5 V
D3B
V REF
V PFD
Dwg. EP-047-5
MIXED DECAY SLOW DECAY MIXED DECAY SLOW DECAY
Figure 5 — Microstepping/Sinusoidal Drive Current
Dwg. WK-004-5
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

12 Page





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