A3982
DMOS Stepper Motor Driver with Translator
Features and Benefits
▪
Low R
DS(on)
outputs
▪
Automatic current decay mode detection/selection
▪
Mixed and Slow current decay modes
▪
Synchronous rectification for low power dissipation
▪
Internal UVLO and thermal shutdown circuitry
▪
Crossover-current protection
Description
The A3982 is a complete stepper motor driver with built-
in translator for easy operation. It is designed to operate
bipolar stepper motors in full- and half-step modes, with an
output drive capacity of up to 35 V and ±2 A. The A3982
includes a fixed off-time current regulator which has the
ability to operate in Slow or Mixed decay modes.
The translator is the key to the easy implementation of the
A3982. Simply inputting one pulse on the STEP input drives
the motor one step. There are no phase sequence tables, high
frequency control lines, or complex interfaces to program.
The A3982 interface is an ideal fit for applications where a
complex microprocessor is unavailable or is overburdened.
The chopping control in the A3982 automatically selects
the current decay mode (Slow or Mixed). When a signal
occurs at the STEP input pin, the A3982 determines if
that step results in a higher or lower current in each of the
motor phases. If the change is to a higher current, then the
decay mode is set to Slow decay. If the change is to a lower
current, then the current decay is set to Mixed (set initially
to a fast decay for a period amounting to 31.25% of the
Package: 24 pin SOICW with internally
fused leads (suffix LB)
Not to scale
Continued on the next page…
Pin-out Diagram
OUT2A
SENSE2
VBB2
OUT2B
ENABLE
PGND
PGND
CP1
CP2
1
2
3
4
5
24 OUT1A
23 SENSE1
22 VBB1
21 OUT1B
20 DIR
Translator
& Control Logic
6
7
8
19 PGND
18 PGND
17 REF
16 STEP
15 VDD
9
VCP 10
VREG 11
MS1 12
Charge
Pump
OSC
Reg
14 ROSC
13 RESET
26184.28C
A3982
DMOS Stepper Motor Driver with Translator
Internal circuit protection includes: thermal shutdown with
hysteresis, undervoltage lockout (UVLO), and crossover-current
protection. Special power-on sequencing is not required.
The A3982 is supplied in a 24-pin wide-body SOIC
(package LB) with internally-fused power ground leads for
enhanced thermal dissipation. It is lead (Pb) free, with 100%
matte tin plated leadframe.
Description (continued)
fixed off-time, then to a slow decay for the remainder of the
off-time). This current decay control scheme results in reduced
audible motor noise, increased step accuracy, and reduced power
dissipation.
Internal synchronous rectification control circuitry is provided to
improve power dissipation during PWM operation.
Selection Guide
Part Number
A3982SLB-T
A3982SLBTR-T
Packing*
31 pieces per tube
1000 pieces per reel
Package
24-pin Wide SOIC with pins 6 and 7, and 18
and 19, fused internally
*Contact Allegro for additional packing options
Absolute Maximum Ratings
Characteristic
Load Supply Voltage
Logic Input Voltage
Sense Voltage
Reference Voltage
Output Current
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
V
BB
V
IN
V
SENSE
V
REF
I
OUT
T
A
T
J
(max)
T
stg
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 150°C.
Range S
Notes
Rating
35
–0.3 to 7
0.5
4
±2
–20 to 85
150
–55 to 150
Units
V
V
V
V
A
ºC
ºC
ºC
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A3982
DMOS Stepper Motor Driver with Translator
Functional Block Diagram
0.1
μF
0.22
μF
VREG
ROSC
CP1
CP2
VDD
Current
Regulator
OSC
Charge
Pump
VCP
REF
DMOS Full Bridge
0.1
μF
VBB1
DAC
OUT1A
OUT1B
PWM Latch
Blanking
Mixed Decay
SENSE1
Gate
Drive
R
S1
VBB2
STEP
DIR
RESET
MS1
Translator
Control
Logic
DMOS Full Bridge
OUT2A
OUT2B
ENABLE
PWM Latch
Blanking
Mixed Decay
SENSE2
R
S2
DAC
V
REF
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A3982
DMOS Stepper Motor Driver with Translator
ELECTRICAL CHARACTERISTICS
1
at T
A
= 25°C, V
BB
= 35 V (unless otherwise noted)
Characteristics
Output Drivers
Load Supply Voltage Range
Logic Supply Voltage Range
Output On Resistance
Body Diode Forward Voltage
Motor Supply Current
Logic Supply Current
Control Logic
Logic Input Voltage
Logic Input Current
Input Hysteresis
Blank Time
Fixed Off-Time
Reference Input Voltage Range
Reference Input Current
Current Trip-Level Error
3
Crossover Dead Time
Protection
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
UVLO Enable Threshold
UVLO Hysteresis
V
IN(1)
V
IN(0)
I
IN(1)
I
IN(0)
V
HYS(IN)
t
BLANK
t
OFF
V
REF
I
REF
err
I
Symbol
V
BB
V
DD
R
DSON
V
F
I
BB
I
DD
Test Conditions
Operating
Operating
Source Driver, I
OUT
= –1.5 A
Sink Driver, I
OUT
= 1.5 A
Source Diode, I
F
= –1.5 A
Sink Diode, I
F
= 1.5 A
f
PWM
< 50 kHz
Operating, outputs disabled
f
PWM
< 50 kHz
Outputs off
Min.
8
3.0
–
–
–
–
–
–
–
–
V
DD
0.7
Typ.
2
–
–
0.370
0.330
–
–
–
–
–
–
–
–
<1.0
<1.0
300
1
30
30
–
0
–
–
475
165
15
2.7
0.10
Max.
35
5.5
0.460
0.380
1.2
1.2
4
2
8
5
–
V
DD
0.3
20
20
500
1.3
40
37
4
3
±5
±5
800
–
–
3
–
Units
V
V
Ω
Ω
V
V
mA
mA
mA
mA
V
V
μA
μA
mV
μs
μs
μs
V
μA
%
%
ns
°C
°C
V
V
V
IN
= V
DD
0.7
–
–20
–20
150
0.7
20
23
0
–3
–
–
100
–
–
2.35
0.05
V
IN
= V
DD
0.3
OSC > 3 V
R
OSC
= 25 kΩ
V
REF
= 2 V,
%I
TripMAX
= 70.71%
V
REF
= 2 V,
%I
TripMAX
= 100.00%
t
DT
T
J
T
JHYS
UV
LO
UV
HYS
V
DD
rising
1
Negative current is defined as coming out of (sourcing from) the specified device pin.
2
Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for
3
err
individual units, within the specified maximum and minimum limits.
I
= (I
Trip
– I
Prog
)
⁄
I
Prog
, where I
Prog
= %I
TripMAX
I
TripMAX
.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A3982
DMOS Stepper Motor Driver with Translator
THERMAL CHARACTERISTICS
Characteristic
Symbol
Test Conditions*
One-layer PCB, one-sided with copper limited to solder pads
Package Thermal Resistance
R
θJA
One-layer PCB, two-sided with copper limited to solder pads and
3.57 in.
2
of copper area on each side, connected to PGND pins
Four-layer PCB, based on JEDEC standard
*Additional thermal information available on Allegro Web site.
Value Units
77
45
35
ºC/W
ºC/W
ºC/W
Power Dissipation versus Ambient Temperature
4.00
3.50
Power Dissipation, P
D
(W)
3.00
2.50
2.00
1.50
1.00
0.50
0
R
θ
J
A
=
35
45
R
ºC
θ
J
/W
/W
A
=
ºC
R
θ
JA
=7
7 ºC
/W
20
40
60
80
100
120
Temperature, T
A
(°C)
140
160
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
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