A3955 Ver la hoja de datos (PDF) - Allegro MicroSystems
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A3955 Datasheet PDF : 13 Pages
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A3955
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 A3955 is 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).
VBB
BRIDGE A
BRIDGE B
V PFD
1
V REF
2
3
4
5
+5 V
6
PHASE A
7
D2A
8
LOGIC
16
47 μF
15
D 0A
14
13
12
1111
10
9
D 1A
D 1B
9
10
11
12
13
D0B
14
15
47 μF
VBB
16
8
D2B
7
PHASE B
6
+5 V
5
LOGIC
4
3
2
V REF
1
V PFD
Dwg. EP-047-3
Figure 4 — Typical Application
MIXED DECAY SLOW DECAY MIXED DECAY SLOW DECAY
Dwg. WK-004-3
Figure 5 — Microstepping/Sinusoidal Drive Current
Allegro MicroSystems, Inc.
10
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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