2W1-2 Phase Excitation/Micro-step Support
A3955SB/SLB
Allegro MicroSystems product
2-Phase Stepper Motor Bipolar Driver ICs
sFeatures
q
Maximum output ratings: 50V,
±1.5A
q
Internal 3-bit non-linear DAC for 8-division
microstepping enables 2W1-2,W1-2, 1-2,
2-phase excitation drive without external
sine wave generator
q
Internal PWM current control in Mixed De-
cay mode (can also be used in Fast Decay
and Slow Decay mode), which improves
motor current response and stability with-
out deterioration of motor iron loss
q
External RC filter for sense terminal not
required thanks to internal blanking circuitry
q
Internal thermal shutdown, crossover-cur-
rent protection and transient-suppression
diodes
q
Special power-up and power-down se-
quencing for motor supply and logic sup-
ply not required
q
Employs copper batwing lead frame with
low thermal resistance
sAbsolute
Maximum Ratings
Parameter
Load supply voltage
Output current (continuous)
Logic supply voltage
Logic/reference input
voltage range
Sense voltage
Package power dissipation
Operating temperature
Junction temperature
Storage temperature
Symbol
V
BB
I
O
V
CC
V
IN
V
S
P
D (Note1)
T
a
T
j
(Note2)
Ratings
A3955SB
50
±1.5
7.0
−0.3
to V
CC
+0.3
1.0
2.90
−20
to +85
+150
−55
to +150
1.86
A3955SLB
Units
V
A
V
V
V
W
°C
°C
°C
T
stg
qOutput
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.
Note 1: When ambient temperature is 25°C or over, derate using
−23.26mW/°C(SB)
or
−14.93mW/°C(SLB).
Note 2: Fault conditions where junction temperature (T
j
) exceeds 150°C will activate the device’s thermal
shutdown circuitry. These conditions can be tolerated but should be avoided.
sTerminal
Connection Diagram
A3955SB/SLB
sDerating
Allowable package power dissipation P
D
[W]
(TOP VIEW)
3.0
2.5
2
1.5
1
0.5
0
−20
A3
95
PFD
REF
RC
GROUND
GROUND
LOGIC
SUPPLY
PHASE
D
2
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
LOAD
SUPPLY
OUT
B
D
0
GROUND
GROUND
SENSE
OUT
A
D
1
5S
B
43
°
C
A3
/W
95
5S
L
B
67
°
C
/W
0
20
40
60
80
100
Ambient temperature Ta (°C)
88
A3955SB/SLB
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