Data Sheet
29319.41
Note the A3955SB (DIP) and the A3955SLB
(SOIC) are electrically identical and share a
common terminal number assignment.
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage, V
BB
. . . . . . . . . . 50 V
Output Current, I
OUT
(Continuous) . . . . . . . . . . . . . .
1.5 A*
Logic Supply Voltage, V
CC
. . . . . . . . . 7.0 V
Logic/Reference Input Voltage Range,
V
IN
. . . . . . . . . . . -0.3 V to V
CC
+ 0.3 V
Sense Voltage, V
S
. . . . . . . . . . . . . . . . 1.0 V
Package Power Dissipation,
P
D
. . . . . . . . . . . . . . . . . . . . See Graph
Operating Temperature Range,
T
A
. . . . . . . . . . . . . . . . . -20C to +85C
Junction Temperature, T
J
. . . . . . . +150C
Storage Temperature Range,
T
S
. . . . . . . . . . . . . . . . -55C to +150C
* 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 temperature
of 150C.
Fault conditions that produce excessive junction
temperature will activate the device's thermal
shutdown circuitry. These conditions can be
tolerated but should be avoided.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
GROUND
GROUND
LOGIC
SUPPLY
PHASE
GROUND
GROUND
RC
SENSE
D
Dwg. PP-056-2
REF
LOAD
SUPPLY
V
CC
OUTB
OUTA
V
BB
LOGIC
PFD
1
D 0
D 2
The A3955SB and A3955SLB are designed for driving one winding
of a bipolar stepper motor in a microstepping mode. The outputs are
rated for continuous output currents to
1.5 A and operating voltages
to 50 V. Internal pulse-width modulated (PWM) current control com-
bined with an internal three-bit nonlinear digital-to-analog converter
allows the motor current to be controlled in full-, half-, quarter-, or
eighth-step (microstepping) modes. Nonlinear increments minimize
the number of control lines necessary for microstepping.
Microstepping provides for increased step resolution, and reduces
torque variations and resonance problems at low speed.
Internal circuitry determines whether the PWM current-control
circuitry operates in a slow (recirculating) current-decay mode, fast
(regenerative) current-decay mode, or in a mixed current-decay mode
in which the off time is divided into a period of fast current decay with
the remainder of the fixed off time spent in slow current decay. The
combination of user-selectable current-sensing resistor and reference
voltage, digitally selected output current ratio; and slow, fast, or mixed
current-decay modes provides users with a broad, variable range of
motor control.
Internal circuit protection includes thermal shutdown with hyster-
esis, transient-suppression diodes, and crossover current protection.
Special power-up sequencing is not required.
The A3955S-- is supplied in a choice of two power packages; a
16-pin dual-in-line plastic package with copper heat-sink tabs (suffix
`B'), and a 16-lead plastic SOIC with copper heat-sink tabs (suffix `LB').
For both package styles, the power tab is at ground potential and
needs no electrical isolation.
FEATURES
s
1.5 A Continuous Output Current
s
50 V Output Voltage Rating
s
Internal PWM Current Control
s
3-Bit Non-Linear DAC
s
Fast, Mixed Fast/Slow, and Slow Current-Decay Modes
s
Internal Transient-Suppression Diodes
s
Internal Thermal-Shutdown Circuitry
s
Crossover-Current and UVLO Protection
FULL-BRIDGE PWM
MICROSTEPPING MOTOR DRIVER
Part Number
Package
A3955SB
16-Pin DIP
A3955SLB
16-Lead SOIC
Always order by complete part number:
3955
3955
FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at T
A
= 25C, V
BB
= 5 V to 50 V, V
CC
= 4.5 V to 5.5 V
(unless otherwise noted.)
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Load Supply Voltage Range
V
BB
Operating, I
OUT
=
1.5 A, L = 3 mH
V
CC
--
50
V
Output Leakage Current
I
CEX
V
OUT
= V
BB
--
<1.0
50
A
V
OUT
= 0 V
--
<-1.0
-50
A
Output Saturation Voltage
V
CE(SAT)
V
S
= 1.0 V:
(Forward or Reverse Mode)
Source Driver, I
OUT
= -0.85 A
--
1.0
1.2
V
Source Driver, I
OUT
= -1.5 A
--
1.3
1.5
V
Sink Driver, I
OUT
= 0.85 A
--
0.5
0.6
V
Sink Driver, I
OUT
= 1.5 A
--
1.3
1.5
V
Sense Current Offset
I
SO
I
S
- I
OUT
, I
OUT
= 850 mA,
20
33
40
mA
V
S
= 0 V, V
CC
= 5 V
Clamp Diode Forward Voltage
V
F
I
F
= 0.85 A
--
1.2
1.4
V
(Sink or Source)
I
F
= 1.5 A
--
1.4
1.7
V
Motor Supply Current
I
BB(ON)
--
2.0
4.0
mA
(No Load)
I
BB(OFF)
D
0
= D
1
= D
2
= 0.8 V
--
1.0
50
A
Continued next page...
Power Outputs
50
75
100
125
150
5
1
0
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
TEMPERATURE IN
C
4
3
2
25
Dwg. GP-049-2A
R = 6.0
C/W
JT
SUFFIX 'B', R = 43
C/W
JA
SUFFIX 'LB', R = 63
C/W
JA
Table 3 -- DAC Truth Table
DAC DATA
Current
D
2
D
1
D
0
Ratio, %
V
REF
/V
S
H
H
H
100
3.00
H
H
L
92.4
3.25
H
L
H
83.1
3.61
H
L
L
70.7
4.24
L
H
H
55.5
5.41
L
H
L
38.2
7.85
L
L
H
19.5
15.38
L
L
L
All Outputs Disabled
where V
S
= I
TRIP
R
S
. See Applications section.
3955
FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
* The total error for the V
REF
/V
S
function is the sum of the D/A error and the current-sense comparator input offset voltage.
Logic Supply Voltage Range
V
CC
Operating
4.5
5.0
5.5
V
Reference Voltage Range
V
REF
Operating
0.5
--
2.5
V
UVLO Enable Threshold
V
CC
= 0
5 V
3.35
3.70
4.05
V
UVLO Hysteresis
0.30
0.45
0.60
V
Logic Supply Current
I
CC(ON)
--
42
50
mA
I
CC(OFF)
D
0
= D
1
= D
2
= 0.8 V
--
12
16
mA
Logic Input Voltage
V
IN(1)
2.0
--
--
V
V
IN(0)
--
--
0.8
V
Logic Input Current
I
IN(1)
V
IN
= 2.0 V
--
<1.0
20
A
I
IN(0)
V
IN
= 0.8 V
--
<-2.0
-200
A
Mixed-Decay Comparator
V
PFD
Slow Current-Decay Mode
3.5
--
--
V
Trip Points
Mixed Current-Decay Mode
1.1
--
3.1
V
Fast Current-Decay Mode
--
--
0.8
V
Mixed-Decay Comparator
V
IO(PFD)
--
0
20
mV
Input Offset Voltage
Mixed-Decay Comparator
V
IO(PFD)
5.0
25
55
mV
Hysteresis
Reference Input Current
I
REF
V
REF
= 0 V to 2.5 V
--
--
5.0
A
Reference Divider Ratio
V
REF
/V
S
at trip, D
0
= D
1
= D
2
= 2 V
--
3.0
--
--
Digital-to-Analog Converter
--
1.0 V < V
REF
2.5 V
--
--
3.0
%
Accuracy*
0.5 V < V
REF
1.0 V
--
--
4.0
%
Current-Sense Comparator
V
IO(S)
V
REF
= 0 V
--
--
5.0
mV
Input Offset Voltage*
Step Reference
SRCR
D
0
= D
1
= D
2
= 0.8 V
--
0
--
%
Current Ratio
D
0
= 2 V, D
1
= D
2
= 0.8 V
--
19.5
--
%
D
0
= 0.8 V, D
1
= 2 V, D
2
= 0.8 V
--
38.2
--
%
D
0
= D
1
= 2 V, D
2
= 0.8 V
--
55.5
--
%
D
0
= D
1
= 0.8 V, D
2
= 2 V
--
70.7
--
%
D
0
= 2 V, D
1
= 0.8 V, D
2
= 2 V
--
83.1
--
%
D
0
= 0.8 V, D
1
= D
2
= 2 V
--
92.4
--
%
D
0
= D
1
= D
2
= 2 V
--
100
--
%
ELECTRICAL CHARACTERISTICS at T
A
= 25C, V
BB
= 5 V to 50 V, V
CC
= 4.5 V to 5.5 V
(unless otherwise noted. )
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Control Circuitry
Continued next page...
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