A3909
Dual Full Bridge Motor Driver
FEATURES AND BENEFITS
DESCRIPTION
• Low RDS(on) outputs
• Drives two DC motors or single stepper motor
• Low power standby (Sleep) mode with zero current drain
• Thermal shutdown protection
• Parallel operation option for 1.8 A, single DC motor
• Overcurrent protection:
▫ Output to supply short
▫ Output to GND short
▫ Output load short
The A3909 is a dual full bridge motor driver, designed for
12 V medium power applications. The outputs are rated for
operation through a power supply range of 4 to 18 V, and
capable of up to 1 A per phase.
Paralleling the outputs is possible for higher amperage single
DC motor applications.
The four inputs (IN1 to IN4) can control DC motors in forward,
reverse, brake, and coast modes, or a bipolar stepper motor in
full- and half-step modes.
The A3909 is supplied in a 10-pin MSOP package with exposed
thermal pad (suffix LY) and a 10-pin SSOP (suffix LN) for
wave solder applications. Both packages are lead (Pb) free
with 100% matte-tin leadframe plating.
PACKAGES:
10-pin MSOP
with exposed thermal pad
(LY package)
10-pin SSOP
(LN package)
Not to scale
Functional Block Diagram
VBB
IN1
Control
Logic
TSD
UVLO
OCP
Disable
Load Supply
VBB
OUT1
OUT1
OUT2
OUT2
GND
GND
Load Supply
VBB
IN2
VBB
IN3
Control
Logic
TSD
UVLO
OCP
Disable
OUT3
OUT3
OUT4
OUT4
VBB
IN4
GND
PAD
LY package
A3909-DS, Rev. 3
MCO-0000529
Configuration
for driving
2 DC motors
Configuration
for parallel operation
at 1.8 A
January 20, 2021
A3909
Dual Full Bridge Motor Driver
SELECTION GUIDE
Part Number
Package
Packing
A3909GLNx-T*
10-pin SSOP
3000 pieces per 13-in. reel
A3909GLYTR-T
10-pin MSOP with
exposed thermal pad
4000 pieces per 13-in. reel
*Contact Allegro Sales for availability of this package option.
ABSOLUTE MAXIMUM RATINGS
Rating
Unit
Supply Voltage
Characteristic
Symbol
VBB
Notes
18
V
Logic Input Voltage Range
VIN
–0.3 to 6
V
Output Current
IOUT
1
A
Output Voltage
VOUT
–0.3 to VBB + 1
V
Operating Ambient Temperature
TA
–40 to 105
°C
Maximum Junction Temperature
TJ(max)
150
°C
Tstg
–55 to 150
°C
Storage Temperature
G temperature range
Thermal Characteristics may require derating at maximum conditions, see application information
Characteristic
Package Thermal Resistance
Symbol
RθJA
Value
Unit
LN package (estimated), on 1-layer PCB with copper limited
to pin area
Test Conditions*
130
°C/W
LY package, on 2-layer PCB with 2.260 in.2 of copper area
each side
48
°C/W
*Additional thermal information available on the Allegro website.
Terminal List Table
Number
Name
1
IN1
Logic input
2
IN2
Logic input
3
VBB
Input supply
4
IN3
Logic input
7 OUT3
5
IN4
Logic input
6 OUT4
6
OUT4
Motor terminal
7
OUT3
Motor terminal
8
GND
Ground
9
OUT2
Motor terminal
10
OUT1
Motor terminal
–
PAD
Pinout Diagram
10 OUT1
IN1 1
IN2 2
VBB 3
IN3 4
IN4 5
PAD
(LY
package)
9 OUT2
8 GND
LN and LY packages
Function
(LY package) Exposed thermal pad
2
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
A3909
Dual Full Bridge Motor Driver
ELECTRICAL CHARACTERISTICS*: Valid at TA = 25°C, unless otherwise specified
Characteristic
Symbol
VBB Voltage Range
VBB
VBB Supply Current
IBB
Total Driver On-Resistance (Sink +
Source)
RDS(on)tot
Test Conditions
Min.
Typ.
Max.
Unit
4
–
18
V
–
4
8
mA
Standby Mode
–
VIN(1)(min), H = voltage high, source driver on, L = voltage low, sink driver on
4
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
A3909
Dual Full Bridge Motor Driver
FUNCTIONAL DESCRIPTION
Device Operation
The 3909 is designed to operate two DC motors or a single
stepper motor. The outputs are PMOS source drivers combined
with low RDS(on) DMOS sink drivers.
turned on. If the current exceeds 1.8 A for longer than 2 µs, then
a fault condition is asserted. The sink driver utilizes a drain-tosource voltage monitor. If the voltage exceeds 2 V for longer than
2 µs, the fault condition is asserted.
Protection circuitry includes internal thermal shutdown, protection against shorted loads, and against outputs shorted to GND
or supply. Undervoltage lockout prevents damage by keeping the
outputs off until the driver has enough voltage to operate normally.
When a fault occurs, the IC immediately disables both sides of
the full bridge where the fault occurred. The full bridge input
commands will be ignored for a 2 ms period before being allowed
to retry. Each channel has independent overcurrent protection.
A low power standby (Sleep) mode is activated when all inputs
are low for longer than 1 ms. Sleep mode disables all of the circuitry making the IC ideal for battery operated applications.
Overcurrent Protection (OCP)
The A3909 is protected against accidental shorts or motor outputs
to ground and supply, as well as a shorted load condition. For
the source drivers, the current is monitored after the MOSFET is
During OCP events, the absolute ratings may be exceeded for a
short period of time before the outputs are disabled.
Thermal Shutdown
If the die temperature increases to TJTSD , then all outputs are disabled until the internal temperature falls below a hysteresis level,
TTSDHYS, of 20°C. Internal UVLO is detected on VBB to prevent
output drivers from turning on when below the UVLO threshold.
DC Motor Timing Diagram
tSTANDBY
IN1
IN2
OUT1
OUT2
Current (12)
2
3
4
1) Low power standby (Sleep) mode (IBB = 0)
2) On, reverse – 100% duty cycle
3) On, forward – 100% duty cycle
4) Slow decay PWM
5
6
7
5) Fast decay PWM
6) Coast
7) Low power standby (Sleep) mode
after tSTANBY (IBB = 0)
5
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
A3909
Dual Full Bridge Motor Driver
Stepper Motor Timing Diagram
tSTANDBY
IN1
IN2
OUT1
OUT2
Current (12)
2
3
4
5
6
7
IN1
IN2
IN3
IN4
Current (12)
Current (34)
1
2
3
4
1
2
3
3
1
I (1/3)
3
4
Full Step
5
6
7
8
1
I (2/4)
I (2/4)
2
4
2
4
5
1
8
6
I (1/3)
7
Half Step
6
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
A3909
Dual Full Bridge Motor Driver
APPLICATION INFORMATION
1
System
Controller
2
Load
Supply
3
4
5
IN1
IN2
A3909
PAD
(LY package)
10
OUT1
9
OUT2
VBB
GND
IN3
OUT3
IN4
OUT4
8
DC Motor
7
6
Configuration for parallel operation with 1.8 A output current capability
LN package board
LY package board via layout for thermal dissipation
VBB
IN1
IN4
6.5 V
50 kΩ
GND
VBB
IN2
IN3
21 V
50 kΩ
OUT1
OUT2
OUT3
OUT4
VBB
21V
Input Output Pin Structures
7
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
A3909
Dual Full Bridge Motor Driver
Package LN, 10-Pin SSOP
4.90 ±0.20
0° to 8°
0.65
10
0.21 ±0.04
3.90 ±0.10
1.00
10
2.25
6.00 ±0.20
4.95
A
1.05 (REF)
1
1.27
0.40
2
2
1
Branded Face
C
PCB Layout Reference View
1.55 ±0.20
0.45
0.30
1.00
BSC
0.25
0.10
For Reference Only; not for tooling use
(reference Allegro MCO-0000061)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A Terminal #1 mark area
B Branding scale and appearance at supplier discretion
C Reference land pattern layout. All pads a minimum of 0.20 mm from all
adjacent pads; adjust as necessary to meet application process
requirements and PCB layout tolerances; when mounting on a multilayer
PCB, thermal vias near the pin lands can improve thermal dissipation
(reference EIA/JEDEC Standard JESD51-7)
NNNNNNN
YYWW
LLLL
1
B Standard Branding Reference View
N = Device part number
= Supplier emblem
Y = Last two digits of year of manufacture
W = Week of manufacture
L = Lot number
8
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
A3909
Dual Full Bridge Motor Driver
Package LY, 10-Pin MSOP
With Exposed Thermal Pad
3.00 ±0.10
0° to 6°
10
0.15 ±0.05
3.00 ±0.10
0.30
0.50
10
1.65
4.88 ±0.20
1.73
4.60
A
0.53 ±0.10
1
2
1
0.25
1.98
1
1
Seating Plane
Gauge Plane
2
2
1.98 MIN
C
B
For Reference Only; not for tooling use (reference Allegro MCO-0000050)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
1.73
A Terminal #1 mark area
B Exposed thermal pad (bottom surface)
10
0.86 ±0.05
C Reference land pattern layout (reference IPC7351 SOP50P490X110-11M)
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances; when
mounting on a multilayer PCB, thermal vias at the exposed thermal pad land
can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5)
SEATING
PLANE
0.27
0.18
0.50
REF
0.05
0.15
9
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
A3909
Dual Full Bridge Motor Driver
Revision History
Number
Date
–
November 15, 2018
Description
Corrected Output Current units in Absolute Maximum Ratings table (page 2)
1
December 6, 2019
Minor editorial updates
2
January 20, 2021
Updated Package Outline Drawing reference numbers (pages 8-9).
Copyright 2021, Allegro MicroSystems.
Allegro MicroSystems reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit
improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the
information being relied upon is current.
Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems assumes no responsibility for its use; nor
for any infringement of patents or other rights of third parties which may result from its use.
Copies of this document are considered uncontrolled documents.
For the latest version of this document, visit our website:
www.allegromicro.com
10
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
