A3986
Dual Full-Bridge MOSFET Driver
with Microstepping Translator
Not for New Design
These parts are in production but have been determined to be
NOT FOR NEW DESIGN. This classification indicates that sale of
this device is currently restricted to existing customer applications.
The device should not be purchased for new design applications
because obsolescence in the near future is probable. Samples are no
longer available.
Date of status change: January 30, 2012
Recommended Substitutions:
For existing customer transition, and for new customers or new appli-
cations, refer to the
A4989.
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, LLC reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The
information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no respon-
sibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
A3986
Dual Full-Bridge MOSFET Driver
with Microstepping Translator
Features and Benefits
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2-wire step and direction interface
Dual full-bridge gate drive for N-channel MOSFETs
Operation over 12 to 50 V supply voltage range
Synchronous rectification
Cross-conduction protection
Adjustable mixed decay
Integrated sinusoidal DAC current reference
Fixed off-time PWM current control
Description
The A3986 is a dual full-bridge gate driver with integrated
microstepping translator suitable for driving a wide range of
higher power industrial bipolar 2-phase stepper motors (typically
30 to 500 W). Motor power is provided by external N-channel
power MOSFETs at supply voltages from 12 to 50 V.
This device contains two sinusoidal DACs that generate the
reference voltage for two separate fixed-off-time PWM current
controllers. These provide current regulation for external power
MOSFET full-bridges.
Motor stepping is controlled by a two-wire step and direction
interface, providing complete microstepping control at full-,
half-, quarter-, and sixteenth-step resolutions. The fixed-off
time regulator has the ability to operate in slow-, mixed-, or
fast-decay modes, which results in reduced audible motor noise,
increased step accuracy, and reduced power dissipation.
The translator is the key to the easy implementation of this
IC. Simply inputting one pulse on the STEP input drives the
motor one step (full, half, quarter, or sixteenth depending on
the microstep select input). There are no phase-sequence tables,
high frequency control lines, or complex interfaces to program.
This reduces the need for a complex microcontroller.
Package: 38 pin TSSOP (suffix LD)
Approximate size
Continued on the next page…
Typical Application Diagram
3986-DS, Rev. 3
A3986
Dual Full-Bridge MOSFET Driver
with Microstepping Translator
In addition to crossover current control, internal circuit protection
provides thermal shutdown with hysteresis and undervoltage lockout.
Special power-up sequencing is not required.
This component is supplied in an 38-pin TSSOP (package LD). The
package is lead (Pb) free, with 100% matte tin leadframe plating.
Description (continued)
The above-supply voltage required for the high-side N-channel
MOSFETs is provided by a bootstrap capacitor. Efficiency is
enhanced by using synchronous rectification and the power FETs
are protected from shoot-through by integrated crossover control
and programmable dead time.
Selection Guide
Part Number
A3986SLDTR-T
Packing
Tape and reel, 4000 pieces per reel
Absolute Maximum Ratings
Characteristic
Supply Voltage
Logic Supply Voltage
Logic Inputs and Outputs
SENSEx pins
Sxx pins
LSSx pins
GHxx pins
GLxx pins
Cxx pins
Operating Ambient Temperature
Junction Temperature
Storage Temperature
T
A
T
J
(max)
T
stg
Range S
Symbol
V
BB
V
DD
Notes
Rating
–0.3 to 50
–0.3 to 7
–0.3 to 7
–1 to 1
–2 to 55
–2 to 5
Sxx to Sxx+15
–2 to 16
–0.3 to Sxx+15
–20 to 85
150
–55 to 150
Units
V
V
V
V
V
V
V
V
V
ºC
ºC
ºC
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A3986
Dual Full-Bridge MOSFET Driver
with Microstepping Translator
Functional Block Diagram
+5 V
VDD
VBB
V
MOTOR
VREG
Bandgap
Regulator
CREG
V
REG
Phase 1A
Bridge1
CBOOT1A
REF
V
REF
High-Side
Drive
V
REG
DAC
STEP
PWM Latch
Blanking
Mixed Decay
Low-Side
Drive
GL1A
LSS1
SENSE1
Phase 1B
Low-Side
Drive
Phase 1
MS2
Phase 1
Control Logic
High-Side
Drive
GH1B
CBOOT1B
C1B
GL1B
S1B
RSENSE1
P
P
C1A
GH1A
S1A
RGH1A
RGH1B
RGL1A
RGL1B
DIR
MS1
Translator
PFD1
Phase 2A
V
MOTOR
Bridge2
C2A
CBOOT2A
PFD2
Phase 2
Control Logic
ENABLE
Phase 2
High-Side
Drive
V
REG
Low-Side
Drive
GH2A
S2A
RGH2A
RGH2B
GL2A
LSS2
SENSE2
RGL2A
RGL2B
RESET
PWM Latch
Blanking
Mixed Decay
Phase 2B
Low-Side
Drive
GL2B
S2B
GH2B
CBOOT2B
C2B
RSENSE2
P
SR
DAC
OSC
ROSC
Protection
UVLO
TSD
V
REF
High-Side
Drive
GND
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A3986
Dual Full-Bridge MOSFET Driver
with Microstepping Translator
ELECTRICAL CHARACTERISTICS at T
A
= 25°C, V
DD
= 5 V, V
BB
= 12 to 50V, unless noted otherwise
Characteristics
Supply and Reference
Load Supply Voltage Range
Load Supply Current
Load Supply Idle Current
Logic Supply Voltage Range
Logic Supply Current
Logic Supply Idle Current
Regulator Output
Bootstrap Diode Forward Voltage
Gate Output Drive
Turn-On Rise Time
Turn-Off Fall Time
Turn-On Propagation Delay
Turn-Off Propagation Delay
Crossover Dead Time
Pull-Up On Resistance
Pull-Down On Resistance
Short-Circuit Current – Source
1
Short-Circuit Current – Sink
GHx Output Voltage
GLx Output Voltage
Logic Inputs
Input Low Voltage
Input High Voltage
Input Hysteresis
Input Current
1
RESET Pulse Width
2
Symbol
V
BB
I
BB
I
BBQ
V
DD
I
DD
I
DDQ
V
REG
V
fBOOT
t
r
t
f
t
p(on)
t
p(off)
t
DEAD
R
OSC
= 10 kΩ, C
LOAD
= 1000 pF
ENABLE = High, outputs disabled
RESET = 0
Test Conditions
Min.
12
–
–
–
3.0
–
–
11.25
0.6
80
40
–
–
0.6
30
14
–140
160
V
C
– 0.2
V
REG
–
0.2
–
0.7 V
DD
150
–1
0.2
Typ.
–
–
–
–
–
–
–
–
0.8
120
60
180
180
–
40
19
–110
200
–
–
–
–
300
–
–
Max.
50
10
6
100
5.5
10
300
13
1
160
80
–
–
1.2
55
24
–80
250
–
–
0.3 V
DD
–
–
1
1
Units
V
mA
mA
μA
V
mA
μA
V
V
ns
ns
ns
ns
μs
Ω
Ω
mA
mA
V
V
V
V
mV
μA
μs
RESET = 0
I
REGInt
= 30 mA
I
fBOOT
= 10 mA
C
LOAD
= 1000 pF, 20% to 80%
C
LOAD
= 1000 pF, 80% to 20%
ENABLE low to gate drive on
ENABLE high to gate drive off
R
OSC
= 10 kΩ,
I
GH
= –25 mA
I
GL
= 25 mA
R
DS(on)UP
R
DS(on)DN
I
SC(source)
I
SC(sink)
V
GHx
CBOOTx fully charged
V
GLx
V
IL
V
IH
V
IHys
I
IN
t
wR
Continued on the next page...
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
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