A3955
Description (continued)
Full-Bridge PWM Microstepping Motor Driver
Internal circuit protection includes thermal shutdown with hysteresis,
transient-suppression diodes, and crossover-current protection.
Special power-up sequencing is not required.
The A3955 is supplied in a choice of two power packages; a 16-pin
dual-in-line plastic package with copper heat-sink tabs (suffix ‘B’),
Selection Guide
Part Number
A3955SB-T
A3955SLB-T
A3955SLBTR-T
and a 16-lead plastic SOIC with internally fused pins (suffix ‘LB’).
For both package styles, the thermally enhanced pins are at ground
potential and need no electrical isolation. Both packages are lead
(Pb) free, with leadframe plating 100% matte tin.
Packing
16-pin DIP with exposed thermal tabs
16-pin SOICW with internally fused pins
16-pin SOICW with internally fused pins
Package
25 per tube
47 per tube
1000 per reel
Absolute Maximum Ratings
Characteristic
Load Supply Voltage
Logic Supply Voltage
Logic/Reference Input Voltage Range
Sense Voltage
Output Current, Continuous
Package Power Dissipation
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
V
BB
V
CC
V
IN
V
S
I
OUT
P
D
T
A
T
J
(max)
T
stg
Range S
Fault conditions that produce excessive junction temperature
will activate the device’s thermal shutdown circuitry. These
conditions can be tolerated but should be avoided.
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 tempera-
ture of 150°C.
Notes
Rating
50
7.0
–0.3 to V
CC
+ 0.3
1.0
±1.5
See graph
–20 to 85
150
–55 to 150
Units
V
V
V
V
mA
W
ºC
ºC
ºC
Thermal Characteristics
Characteristic
Package Thermal Resistance, Junction
to Ambient
Package Thermal Resistance, Junction
to Tab
Symbol
R
θJA
Test Conditions*
2
B Package, single-layer PCB, 1 in. 2-oz. exposed copper
2
LB Package, 2-layer PCB, 0.3 in. 2-oz. exposed copper each
side
Value
43
67
6
Units
ºC/W
ºC/W
ºC/W
R
θJT
*Additional thermal information available on Allegro website.
ALLOWABLE PACKAGE POWER DISSIPATION (W)
4
R
θJT
= 6.0°C/W
3
SUFFIX 'B', R
θJA
= 43°C/W
2
1
SUFFIX 'LB', R
θJA
= 67°C/W
0
25
50
75
100
TEMPERATURE IN °C
125
150
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
