urrent Buck Regulators
Integrated Constant-Current Buck Regulators
National Semiconductor offers a broad portfolio of easy to design, energy-efficient buck regulators
ideal for driving LEDs in a wide variety of applications. With integrated switching MOSFETs and
online design tools as well as extensive protection features and dimming capability, Nationals buck
LED drivers maximize ease of design without sacrificing functionality. Nationals LED drivers also
feature low feedback voltages and very high efficiencies to enable energy-efficient lighting solutions.
Online design tools ease
IC selection, enable design
simulation, and offer orderable
evaluation kits with custom BOMs
Low external component counts
Fast PWM dimming inputs
Low ( 200 mV) feedback voltages
Thermal, open-circuit, and
short-circuit protection
Benefits
Design tools and integrated switches
increase ease of design and time to market
Low external component counts minimize
BOM cost and total solution size
Low feedback voltages, high efficiencies,
and excellent package technologies
maximize heat dissipation
Wide input voltage ranges and high current
capabilities increase design flexibility
Supports all ceramic output capacitors
and capacitor-less outputs for smallest
solution size
Applications
General illumination
Automotive lighting
Industrial lighting
Architectural lighting
Signage
Features
L E D D R I V E R S : I C s
5 5
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LM3405/05A schematic
The LM3405/05A are 1A constant-current buck regulators designed
to provide simple, high-efficiency solutions for driving high-power LEDs.
These devices feature a low 205 mV feedback voltage to reduce heat
dissipation, and can support up to five 1W or 3W LEDs in series
Visit lighting.arrow.com/designtools to access free design tools, including Nationals LED reference designs and LED WEBENCH online tools.
LM3402/02HV evaluation board with
female 6-pin SIP connector and two
standard 94 mil turret connectors for
easy connection to LED array
*Diagnostic capabilities: TSD: Thermal shutdown, OVM: Output voltage monitoring, UVLO: Under voltage lock out, LOD: LED open detection
Product Specifications
Part Number
Type
Dimming
Type
Number
of LEDs/
String
Number
of Strings Configuration
Input
Voltage
(VDC)
Output
Voltage
(VDC)
Output
Current
(mA)
Peak
Efficiency
(%)
Diagnostic Capabilities*
Interface
Markets
LM3402
Buck
PWM
1-10
1
Series
6-42
40
500
90
Over-current protection/TSD/LOD
PWM
LM3402HV
PWM
1-20
1
Series
6-75
70
500
90
Over-current protection/TSD/LOD
PWM
LM3404
PWM
1-10
1
Series
6-42
40
1,000
90
Over-current protection/TSD/LOD
PWM
LM3404HV
PWM
1-20
1
Series
6-75
70
1,000
90
Over-current protection/TSD/LOD
PWM
LM3405
PWM
1-4
1
Series
3-15
14
1,000
90
Over-current protection/TSD/LOD/OVM/UVLO
PWM
LM3405A
PWM
1-5
1
Series
3-22
20
1,000
90
Over-current protection/TSD/LOD/OVM/UVLO
PWM
LM3406
PWM
1-10
1
Series
6-42
40
1,500
90
TSD, UVLO, broken open check LM3406HV
PWM
1-20
1
Series
6-75
70
1,500
90
TSD, UVLO, broken open check LM3407
PWM
1-7
1
Series
4.5-30
27
350
96
Over-current protection/ TSD/LOD/UVLO
PWM
M
MA
AR
RK
KE
ET
TS
S L
LE
EG
GE
EN
ND
D
COMMERCIAL LIGHTING
FLASHLIGHTS
TRANSPORTATION
BACKLIGHTING
SIGNAGE
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LM3406 schematic
The LM3406/06HV are monolithic switching regulators capable of
delivering up to 1.5A constant currents to high-power LEDs. True average
current control, broken and open LED protection, low-power shutdown,
and thermal shutdown features allow for design robustness and flexibility 5 6
L E D D R I V E R S : I C s
Constant-Current Boost Regulators
Nationals portfolio of constant-current boost regulators features inductive and switched-capacitor
solutions for applications such as backlighting, flash, and portable lighting. For higher currents,
National has a variety of high-efficiency inductive-boost LED drivers. Nationals switched-capacitor
LED drivers offer small, inductor-less, low-noise solutions for both parallel and series LED
configurations. Features such as multiple dimming interfaces and current matching can also
be found in inductive and switched capacitor drivers.
PWM, analog, and I
2
C
dimming interfaces
128 logarithmic dimming steps
Built-in current matching
Adjustable and fixed switching
frequency options
Thermal shutdown, flash timeout, open-
circuit, and short-circuit protection
Supports OLED displays
Benefits
Multiple dimming interfaces
increases design flexibility
Current matching ensures parallel
LED arrays have even, balanced
brightness
Various switching frequency options
allow for solution size, efficiency,
and EMI optimization
Micro SMD packages provide very
small footprints and minimize
solution size
Applications
Backlighting
Flash LED
Portable lighting
(handheld devices,
flashlights)
Automotive lighting
Features
LM3431 schematic
The LM3431 is a 3-channel linear current controller combined with
a boost-switching controller ideal for driving LED backlight panels in
space-critical applications. It accepts both analog and digital control
signals and can achieve contrast ratios greater than 1,000:1
*Diagnostic capabilities: TSD: Thermal shutdown, UVLO: Under voltage lock out, LOD: LED open detection
Arrow Electronics Lighting Group
1.888.9LIGHT1
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Product Specifications
Part Number
Type
Dimming
Type
Number
of LEDs/
String
Number
of Strings
Configuration
Input
Voltage
(VDC)
Output
Voltage
(VDC)
Output
Current (mA)
Peak
Efficiency
(%)
Diagnostic Capabilities*
Interface
Markets
LM3410
Boost/SEPIC
PWM
1-6
1
Series
2.7-5.5
24
1,000
88
Over-current protection/TSD/LOD
PWM
LM3430/32
Boost
PWM/analog
1-20
6
Series/parallel
6-40
80
40 per string
92
Over-current protection/
TSD/LOD/UVLO
PWM/analog
LM3431
PWM/analog
1-10
3
Series/parallel
5-36
40
150 per string
88
Over-current protection/
TSD/OVM/LOD
PWM/analog
LM3509
I
2
C
1-5
2
Series/parallel/OLED
2.7-5.5
21
30 per string
92
TSD/soft start
I
2
C
LM2756
I
2
C
1
8
Parallel
2.7-5.5
4.6
180
91
TSD/OVP/soft start
I
2
C
LM2757 1-10
2.7-5.5
4.1/4.5/5
180
92
Over-current protection/
TSD/shutdown w/high
impedence/soft start
Binary
LM3553 1-2
1
Series
2.7-5.5
19
1,200
90
TSD/OVM/Flash pulse safety timer
I
2
C
LM4510 Series/parallel/
OLED
2.7-5.5
18
280
85
TSD/output short-circuit
protection/feedback fault
protection/input UVLO/soft
start/true shutdown isolation
Binary
LM2755
I
2
C
1
3
Parallel
3-5.5
5
90
90
TSD/soft start
I
2
C
LM3528
Exponential
6
2
Series/parallel
2.7-5.5
20
30
1.27M
LM5022
Boost/SEPIC/
flyback
PWM
1-20
1
Series
6-60
80
1,000
95
Over-current protection/
TSD/LOD/UVLO
PWM
M
MA
AR
RK
KE
ET
TS
S L
LE
EG
GE
EN
ND
D
COMMERCIAL LIGHTING
FLASHLIGHTS
TRANSPORTATION
BACKLIGHTING
SIGNAGE
The LM3528 is a high-efficiency boost
converter for white LEDs and/or OLED
displays with dual-current sinks and I
2
C-
compatible brightness control. This LED
driver is ideal for small- to medium-sized
displays in battery-powered applications
LM3410 schematic
The LM3410 is a high-frequency, very small, constant-current boost
LED driver. A low external component count makes this driver easy
to design and minimizes the total solution size and cost. The LM3410
has an input voltage range down to 2.7V to support single Li-Ion cells Arrow Electronics Lighting Group
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High-Current LED Drivers
National offers buck and boost regulators that can drive up to and greater than 6A, ideal for
applications such as backlighting and projection. For example, the LM3433 supports over 6A
of current and allows the LED anodes to be tied directly to the chassis ground for optimal heat
dissipation. Also, Nationals LM3401 buck regulator is capable of achieving 100 percent duty
cycle in order to support a maximum number of LEDs.
PWM and analog dimming interfaces
Capable of achieving up to 100%
duty cycles
Common-anode configuration allows
LED anodes to be tied directly to
chassis ground
Adjustable switching frequencies
up to 2 MHz
Supports high-current applications with
buck, boost, SEPIC, and flyback solutions
Benefits
Common-anode configuration
maximizes heat dissipation and
reduces heat sink requirements
High duty cycles allow maximum
number of LEDs to be powered
by a single LED driver to shrink
solution size and cost
Multiple dimming interfaces
provide design flexibility
Adjustable switching frequency
options allow for solution size,
efficiency, and EMI optimization
Applications
Backlighting
Projection
Automotive lighting
Industrial lighting
General illumination
Features
L E D D R I V E R S : I C s
5 7
Product Specifications
Part
Number
Type
Dimming
Type
Number
of LEDs/
String
Number
of Strings Configuration
Input
Voltage
(VDC)
Output
Voltage
(VDC)
Output
Current
(mA)
Peak
Efficiency
(%)
Diagnostic Capabilities*
Interface
Markets
LM3433
Buck
PWM/analog
1
1
Series
-9 to -14
-6
>6,000
96
TSD/LOD
PWM/analog
LM3401
PWM
1-9
1
Series
4.5 to 35
35
>3,000
95
TSD/LOD
PWM
LM3421/3 Buck/boost/flyback/SEPIC
PWM
1-20
1
Series
4.5V to 75V
75V
>2,000
2.0 MHz OVP, FLT, LED ready, broken open check
PWM
LM5022
Boost/SEPIC/flyback
PWM
1-20
1
Series
6 to 60
80
>1,000
95
TSD/LOD
PWM
M
MA
AR
RK
KE
ET
TS
S L
LE
EG
GE
EN
ND
D
COMMERCIAL LIGHTING
FLASHLIGHTS
TRANSPORTATION
BACKLIGHTING
SIGNAGE
The LM3433 is an adaptive, constant,
on-time buck controller designed to
provide constant current for illuminating
high-power LEDs. It can drive currents
greater than 6A and supports a
thermal, performance-enhancing
common-anode LED configuration
LM3421/23 schematic
LM3421/23 devices are versatile high voltage LED controllers with the
capability to be configured in a buck, boost, buck-boost, or SEPIC
topology. Zero current shutd