A3957SLB Allegro, A3957SLB Datasheet - Page 12

• Manufacturer Part Number: A3957SLB
• Description: Full Bridge PWM Motor Driver 5V 24-Pin SOIC W
• Manufacturer: Allegro
• Type: Full Bridge PWM Motor Driverr

Specifications of A3957SLB

• Package: 24SOIC W
• Operating Supply Voltage: 5 V
• Maximum Operating Current: 4 mA
• Operating Temperature: -20 to 85 °C

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
3957
FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER
PHASE
V
V
+5 V
D 3A
D 2A
PFD
REF
A
10
11
12
8
9
2
3
4
5
6
7
1
V
NC
NC
NC
CC
Figure 5 — Microstepping/Sinusoidal Drive Current
MIXED DECAY
BRIDGE A
LOGIC
V
BB
Figure 4 — Typical Application
NC
NC
NC
NC
16
15
14
13
22
21
20
19
18
17
24
23
11
SLOW DECAY
V
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
BB
47 F
D 0A
D 1A
MIXED DECAY
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 t
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).
D 1B
D 0B
V
47 F
BB
18
19
21
22
23
24
17
20
13
14
15
16
NC
NC
NC
NC
SLOW DECAY
BRIDGE B
V
BB
LOGIC
OFF
. When the load current is
V
NC
NC
NC
CC
12
11
10
7
6
5
4
2
1
9
8
3
Dwg. WK-004-5
Dwg. EP-047-5
D 2B
PHASE
+5 V
D 3B
V
V
REF
PFD
B