A3957SLB View Datasheet(PDF) - Allegro MicroSystems
Part Name
Description
MFG CO.
'A3957SLB' PDF : 16 Pages View PDF
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
VBB
NC 24
23
3
4 NC
5
22
NC 21
20
47 µF
D 0A
6
19
LOGIC
7
181
8
17
9 VCC
10
NC 16
15
11
NC 14
12 NC
13
D 1A
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
7
LOGIC
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
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