A3989
Bipolar Stepper and High Current DC Motor Driver
Features and Benefits
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36 V output rating
2.4 A DC motor driver
1.2 A bipolar stepper driver
Synchronous rectification
Internal undervoltage lockout (UVLO)
Thermal shutdown circuitry
Crossover-current protection
Very thin profile QFN package
Description
The A3989 is designed operate at voltages up to 36 V while driving
one bipolar stepper motor, at currents up to 1.2A, and one DC motor,
at currents up to 2.4 A. The A3989 includes a fixed off-time pulse
width modulation (PWM) regulator for current control. The stepper
motor driver features dual 2-bit nonlinear DACs (digital-to-analog
converters) that enable control in full, half, and quarter steps. The
DC motor is controlled using standard PHASE and ENABLE signals.
Fast or slow current decay is selected via the MODE pin. The PWM
current regulator uses the Allegro
™
patented mixed decay mode for
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.
Protection features include thermal shutdown with hysteresis,
undervoltage lockout (UVLO) and crossover current protection.
Special power up sequencing is not required.
The A3989 is supplied in a leadless 6 mm × 6 mm × 0.9 mm,
36 pin QFN package with exposed power tab for enhanced thermal
performance. The package is lead (Pb) free, with 100% matte tin
leadframe plating.
Package: 36 pin QFN with exposed thermal pad
0.90 mm nominal height (suffix EV)
Approximate scale 1:1
0.1
μF
50 V
CP1
VDD
0.1
μF
50 V
CP2
VCP
VBB
VBB
OUT1A
OUT1B
100
μF
50 V
0.22
μF
50 V
PHASE1
I01
Microcontroller or
Controller Logic
I11
PHASE2
I02
I12
PHASE3
ENABLE
MODE
VREF1
VREF2
VREF3
SENSE1
A3989
OUT2A
OUT2B
SENSE2
OUT3A
OUT3A
OUT3B
OUT3B
SENSE3
GND
GND
SENSE3
Figure 1. Typical application circuit
A3989DS, Rev. 3
A3989
Selection Guide
Part Number
A3989SEV-T
A3989SEVTR-T
Bipolar Stepper and High Current DC Motor Driver
Packing
61 pieces per tube
1500 pieces per reel
Absolute Maximum Ratings
Characteristic
Load Supply Voltage
Logic Supply Voltage
Symbol
V
BB
V
DD
Stepper motor driver, continuous
Output Current
*
I
OUT
Stepper motor driver, pulsed t
w
< 1
μs
Dc motor driver, continuous
Dc motor driver, pulsed t
w
< 1
μs
Logic Input Voltage Range
SENSEx Pin Voltage
VREFx Pin Voltage
Operating Temperature Range
Junction Temperature
Storage Temperature Range
V
IN
V
SENSEx
V
REFx
T
A
T
J
(max)
T
stg
Range S
Pulsed t
w
< 1
μs
Pulsed t
w
< 1
μs
Notes
Rating
-0.5 to 36
38
–0.4 to 7
1.2
2.8
2.4
3.5
–0.3 to 7
0.5
2.5
2.5
–20 to 85
150
–55 to 150
Units
V
V
V
A
A
A
A
V
V
V
V
ºC
ºC
ºC
* 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.
Thermal Characteristics (may require derating at maximum conditions)
Characteristic
Package Thermal Resistance
Symbol
R
θJA
Test Conditions
EV package, 4 layer PCB based on JEDEC standard
Min. Units
27
ºC/W
Power Dissipation versus Ambient Temperature
5500
5000
4500
4000
Power Dissipation, P
D
(mW)
3500
3000
2500
2000
1500
1000
500
0
25
50
75
100
125
Temperature (°C)
150
175
EV Package
4-layer PCB
(R
JA
= 27 ºC/W)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A3989
Bipolar Stepper and High Current DC Motor Driver
Functional Block Diagram
0.1
μF
50 V
100
μF
50 V
0.22
μF
50 V
0.1
μF
50 V
To
V
BB2
VCP
VBB
VBB
CP1
CP2
VDD
DMOS
Full Bridge 1
VBB1
OSC
CHARGE PUMP
V
CP
OUT1A
PHASE1
I01
I11
PHASE2
I02
I12
OUT1B
Control Logic
Stepper Motor
GATE
DRIVE
SENSE1
R
S1
DMOS
Full Bridge 2
VBB1
Sense1
VREF1
3
-
+
PWM Latch
BLANKING
OUT2A
VREF2
3
Sense 2
+
PWM Latch
BLANKING
OUT2B
V
CP
-
PHASE3
ENABLE
MODE
Control Logic
DC Motor
Sense 2
Sense 3
SENSE2
R
S2
GATE
DRIVE
OUT3A
OUT3A
-
Sense 3
VREF3
3
+
PWM Latch
BLANKING
DMOS
Full Bridge 3
OUT3B
OUT3B
SENSE3
SENSE3
R
S3
GND
GND
NC
NC
NC
NC
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A3989
Characteristics
Load Supply Voltage Range
Logic Supply Voltage Range
VDD Supply Current
Bipolar Stepper and High Current DC Motor Driver
Typ.
2
–
–
7
350
350
700
700
–
–
–
ELECTRICAL CHARACTERISTICS
1
, valid at T
A
= 25 °C, V
BB
= 36 V, unless otherwise noted
Symbol
V
BB
V
DD
I
DD
R
DS(on)DC
R
DS(on)st
Source driver, I
OUT
= –1.2 A, TJ = 25°C
Sink driver, I
OUT
= 1.2 A, TJ = 25°C
Source driver, I
OUT
= –1.2 A, TJ = 25°C
Sink driver, I
OUT
= 1.2 A, TJ = 25°C
I
OUT
= 1.2 A
I
DSS
I
BB
V
IN(1)
V
IN(0)
I
IN
V
hys
PWM change to source on
Propagation Delay Times
t
pd
PWM change to source off
PWM change to sink on
PWM change to sink off
Crossover Delay
Blank Time (DC motor driver)
Blank Time (stepper motor driver)
VREFx Pin Input Voltage Range
VREFx Pin Reference Input Current
Current Trip-Level Error
3
Protection Circuits
VBB UVLO Threshold
VBB Hysteresis
VDD UVLO Threshold
VDD Hysteresis
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
1
For
2
Typical
Test Conditions
Operating
Operating
Min.
8.0
3.0
–
–
–
–
–
–
–20
–
Max.
36
5.5
10
450
450
800
800
1.3
20
8
Units
V
V
mA
mΩ
mΩ
mΩ
mΩ
V
μA
mA
Output On Resistance (DC motor driver)
Output On Resistance (stepper motor
driver)
V
f
, Outputs
Output Leakage
VBB Supply Current
Control Logic
Logic Input Voltage
Logic Input Current
Input Hysteresis
Outputs, V
OUT
= 0 to V
BB
I
OUT
= 0 mA, outputs on, PWM = 50 kHz,
DC = 50%
0.7×V
DD
–
V
IN
= 0 to 5 V
–20
150
350
35
350
35
300
2.5
0.7
Operating
V
REF
= 1.5
V
REF
= 1.5, phase current = 100%
V
REF
= 1.5, phase current = 67%
V
REF
= 1.5, phase current = 33%
0.0
–
–5
–5
–15
7.3
400
V
DD
rising
2.65
75
155
–
–
–
<1.0
300
550
–
550
–
425
3.2
1
–
–
–
–
–
7.6
500
2.8
105
165
15
–
0.3×V
DD
20
500
1000
300
1000
250
1000
4
1.3
1.5
±1
5
5
15
7.9
600
2.95
125
175
–
V
V
μA
mV
ns
ns
ns
ns
ns
μs
μs
V
μA
%
%
%
V
mV
V
mV
°C
°C
t
COD
t
BLANKdc
t
BLANKst
V
REFx
I
REF
V
ERR
V
UV(VBB)
V
UV(VBB)hys
V
UV(VDD)
V
UV(VDD)hys
T
JTSD
T
JTSDhys
V
BB
rising
input and output current specifications, negative current is defined as coming out of (sourcing) the specified device pin.
data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for indi-
vidual units, within the specified maximum and minimum limits.
3
V
ERR
= [(V
REF
/3) – V
SENSE
] / (V
REF
/3).
DC Control Logic
PHASE
ENABLE
MODE
OUTA
OUTB
Function
1
1
1
H
L
Forward (slow decay SR)
1
1
0
H
L
Forward (fast decay SR)
0
1
1
L
H
Reverse (slow decay SR)
0
1
0
L
H
Reverse (fast decay SR)
X
0
1
L
L
Brake (slow decay SR)
1
0
0
L
H
Fast decay SR*
0
0
0
H
L
Fast decay SR*
* To prevent reversal of current during fast decay SR – the outputs will go to the high impedance state as the current gets near zero.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A3989
Bipolar Stepper and High Current DC Motor Driver
Functional Description
Device Operation
The A3989 is designed to operate one
DC motor and one bipolar stepper motor. The currents in each of
the full bridges, all N-channel DMOS, are regulated with fixed
off-time pulse width modulated (PWM) control circuitry. The
peak current in each full bridge is set by the value of an external
current sense resistor, R
Sx
, and a reference voltage, V
REFx
.
If the logic inputs are pulled up to VDD, it is good practice to use
a high value pullup resistor in order to limit current to the logic
inputs should an overvoltage event occur. Logic inputs include:
PHASEx, I0x, I1x, ENABLE, and MODE.
Blanking
This function blanks the output of the current sense
comparator when the outputs are switched by the internal current
control circuitry. The comparator output is blanked to prevent
false detections of overcurrent conditions, due to reverse recovery
currents of the clamp diodes, or to switching transients related to
the capacitance of the load. Dc motors require more blank time
than stepper motors. The stepper driver blank time, t
BLANKst
,
is approximately 1
s.
The DC driver blank time, t
BLANKdc
, is
approximately 3
s.
Control Logic
Stepper motor communication is implemented
via industry standard I1, I0, and PHASE interface. This commu-
nication logic allows for full, half, and quarter step modes. Each
bridge also has an independent V
REF
input so higher resolution step
modes can be programmed by dynamically changing the voltage on
the corresponding VREFx pin. The DC motor is controlled using
standard PHASE, ENABLE communication. Fast or slow current
decay during the off-time is selected via the MODE pin.
Internal PWM Current Control
Each full-bridge is
controlled by a fixed off-time PWM current control circuit that
limits the load current to a user-specified value, I
TRIP
. Initially,
a diagonal pair of source and sink DMOS outputs are enabled
and current flows through the motor winding and R
Sx
. When the
voltage across the current sense resistor equals the voltage on the
VREFx pin, the current sense comparator resets the PWM latch,
which turns off the source driver.
The maximum value of current limiting is set by the selection of
R
S
and the voltage at the VREF input with a transconductance
function approximated by:
I
TripMax
= V
REF
/ (3×R
S
)
Charge Pump (CP1 and CP2)
The charge pump is used to
generate a gate supply greater than the V
BB
in order to drive the
source-side DMOS gates. A 0.1
F
ceramic capacitor should be
connected between CP1 and CP2 for pumping purposes. A 0.1
F
ceramic capacitor is required between VCP and VBBx to act as a
reservoir to operate the high-side DMOS devices.
The stepper motor outputs will define each current step as a
percentage of the maximum current, I
TripMax
. The actual current at
Shutdown
In the event of a fault (excessive junction tem-
perature, or low voltage on VCP), the outputs of the device are
each step I
Trip
is approximated by:
disabled until the fault condition is removed. At power-up, the
I
Trip
= (% I
TripMax
/ 100) I
TripMax
undervoltage lockout (UVLO) circuit disables the drivers.
where % I
TripMax
is given in the Step Sequencing table.
Synchronous Rectification
When a PWM-off cycle is
Note: It is critical to ensure that the maximum rating of
500
mV triggered by an internal fixed off-time cycle, load current will
on each SENSEx pin is not exceeded.
recirculate. The A3989 synchronous rectification feature will
turn on the appropriate MOSFETs during the current decay. This
Fixed Off-Time
The internal PWM current control circuitry
effectively shorts the body diode with the low R
DS(on)
driver. This
uses a one shot circuit to control the time the drivers remain off.
The one shot off-time, t
off
, is internally set to 30
μs.
significantly lowers power dissipation. When a zero current level
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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