Texas Instruments Incorporated LM3404, LM3404HV User's Guide

GND

DIM

BOOT SW

CS

RON

LM3404/04HV

VIN

D1

L1

C

B

R

SNS

C

F

R

ON

C

IN

V

IN

I

F

VCC

LM3404, LM3404HV

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1.0A Constant Current Buck Regulator for Driving High Power LEDs

Check for Samples: LM3404, LM3404HV

1

FEATURES

2

• Integrated 1.0A MOSFET

• VINRange 6V to 42V (LM3404)

• VINRange 6V to 75V (LM3404HV)

• 1.2A Output Current Over Temperature

• Cycle-by-Cycle Current Limit

• No Control Loop Compensation Required

• Separate PWM Dimming and Low Power
Shutdown

• Supports All-ceramic Output Capacitors and
Capacitor-less Outputs

• Thermal Shutdown Protection

• SOIC-8 Package, So PowerPAD-8 Package

APPLICATIONS

• LED Driver

• Constant Current Source

• Automotive Lighting

• General Illumination

• Industrial Lighting

SNVS465F –OCTOBER 2006–REVISED MAY 2013

DESCRIPTION

The LM3404/04HV are monolithic switching
regulators designed to deliver constant currents to
high power LEDs. Ideal for automotive, industrial, and
general lighting applications, they contain a high-side
N-channel MOSFET switch with a current limit of

1.5A (typical) for step-down (Buck) regulators.
Hysteretic controlled on-time and an external resistor
allow the converter output voltage to adjust as
needed to deliver a constant current to series and
series-parallel connected LED arrays of varying
number and type. LED dimming via pulse width
modulation (PWM), broken/open LED protection, low­power shutdown and thermal shutdown complete the
feature set.

Typical Application

1

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

Copyright © 2006–2013, Texas Instruments Incorporated

SW

1

RON

2

VIN

3

BOOT

4

VCC

8

GND

7

DIM

6

CS

5

SW

1

RON

2

VIN

3

BOOT

4

VCC

8

GND

7

DIM

6

CS

5

DAP

LM3404, LM3404HV

SNVS465F –OCTOBER 2006–REVISED MAY 2013

Connection Diagrams

Figure 1. 8-Lead Plastic SOIC-8 Package Figure 2. 8-Lead Plastic So PowerPAD-8 Package

PIN DESCRIPTIONS

Pin(s) Name Description Application Information

1 SW Switch pin Connect this pin to the output inductor and Schottky diode.
2 BOOT MOSFET drive bootstrap pin Connect a 10 nF ceramic capacitor from this pin to SW.
3 DIM Connect a logic-level PWM signal to this pin to enable/disable the power

4 GND Ground pin Connect this pin to system ground.
5 CS Set the current through the LED array by connecting a resistor from this pin to

6 RON On-time control pin A resistor connected from this pin to VIN sets the regulator controlled on-time.
7 VCC Output of the internal 7V linear Bypass this pin to ground with a minimum 0.1 µF ceramic capacitor with X5R or

8 VIN Nominal operating input range for this pin is 6V to 42V (LM3404) or 6V to 75V

DAP GND Thermal Pad Connect to ground. Place 4-6 vias from DAP to bottom layer ground plane.

Input for PWM dimming

Current sense feedback pin

MOSFET and reduce the average light output of the LED array.

ground.

regulator X7R dielectric.
Input voltage pin

(LM3404HV).

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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.

ABSOLUTE MAXIMUM RATINGS(LM3404)

(1)

SNVS465F –OCTOBER 2006–REVISED MAY 2013

If Military/Aerospace specified devices are required, please contact the Texas Instruments Semiconductor Sales
Office/ Distributors for availability and specifications.

VALUE / UNIT

VIN to GND –0.3 V to 45 V
BOOT to GND –0.3 V to 59 V
SW to GND –1.5 V to 45 V
BOOT to VCC –0.3 V to 45 V
BOOT to SW –0.3 V to 14 V
VCC to GND –0.3 V to 14 V
DIM to GND –0.3 V to 7 V
CS to GND –0.3 V to 7 V
RON to GND –0.3 V to 7 V
Junction Temperature 150°C
Storage Temp. Range –65°C to 125°C
ESD Rating
Soldering Information Lead Temperature (Soldering, 10sec) 260°C

(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for

which the device is intended to be functional, but specific performance is not ensured. For specifications and the test conditions, see
Electrical Characteristics.

(2) The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.

(2)

Infrared/Convection Reflow (15sec) 235°C

2 kV

RECOMMENDED OPERATING CONDITIONS (LM3404)

V

IN

Junction Temperature Range –40°C to +125°C
Thermal Resistance θJA(SOIC-8 Package) 155°C/W
Thermal Resistance θJA(So PowerPAD-8 Package)

(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for

which the device is intended to be functional, but specific performance is not ensured. For specifications and the test conditions, see
Electrical Characteristics.

(2) θJAof 50°C/W with DAP soldered to a minimum of 2 square inches of 1oz. copper on the top or bottom PCB layer.

(2)

(1)

VALUE / UNIT

6V to 42V

50°C/W

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SNVS465F –OCTOBER 2006–REVISED MAY 2013

ABSOLUTE MAXIMUM RATINGS (LM3404HV)

VIN to GND –0.3 V to 76 V
BOOT to GND –0.3 V to 90 V
SW to GND –1.5 V to 76 V
BOOT to VCC –0.3 V to 76 V
BOOT to SW –0.3 V to 14 V
VCC to GND –0.3 V to 14 V
DIM to GND –0.3 V to 7 V
CS to GND –0.3 V to 7 V
RON to GND –0.3 V to 7 V
Junction Temperature 150°C
Storage Temperature Range –65°C to 125°C
ESD Rating
Soldering Information Lead Temperature (Soldering, 10sec) 260°C

(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for

which the device is intended to be functional, but specific performance is not ensured. For specifications and the test conditions, see
Electrical Characteristics.

(2) The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.

(2)

RECOMMENDED OPERATING CONDITIONS (LM3404HV)

V

IN

Junction Temperature Range –40°C to +125°C
Thermal Resistance θJA(SOIC-8 Package) 155°C/W
Thermal Resistance θJA(So PowerPAD-8 Package)

(2)

(1)

Infrared/Convection Reflow (15sec) 235°C

(1)

VALUE / UNIT

6 V to 75 V

50°C/W

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VALUE / UNIT

2 kV

(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for

which the device is intended to be functional, but specific performance is not ensured. For specifications and the test conditions, see
Electrical Characteristics.

(2) θJAof 50°C/W with DAP soldered to a minimum of 2 square inches of 1oz. copper on the top or bottom PCB layer.

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SNVS465F –OCTOBER 2006–REVISED MAY 2013

ELECTRICAL CHARACTERISTICS
LM3404

VIN= 24V unless otherwise indicated. Typicals and limits appearing in plain type apply for TA= TJ= 25°C.
in boldface type apply over full Operating Temperature Range. Datasheet min/max specification limits are specified by
design, test, or statistical analysis.

Symbol Parameter Conditions Min Typ Max Units

SYSTEM PARAMETERS

t

ON-1

t

ON-2

(1) Typical specifications represent the most likely parametric norm at 25°C operation.

On-time 1 VIN= 10V, RON= 200 kΩ 2.1 2.75 3.4 µs
On-time 2 VIN= 40V, RON= 200 kΩ 515 675 835 ns

(1)

Limits appearing

LM3404HV

Symbol Parameter Conditions Min Typ Max Units

SYSTEM PARAMETERS

t

ON-1

t

ON-2

LM3404/LM3404HV

Symbol Parameter Conditions Min Typ Max Units

REGULATION AND OVER-VOLTAGE COMPARATORS

V

REF-REG

V

REF-0V

I

CS

SHUTDOWN

V

SD-TH

V

SD-HYS

OFF TIMER

t

OFF-MIN

INTERNAL REGULATOR

V

CC-REG

V

IN-DO

V

CC-BP-TH

V

CC-BP-HYS

V

CC-Z-6

V

CC-Z-8

V

CC-Z-24

V

CC-LIM

V

CC-UV-TH

V

CC-UV-HYS

V

CC-UV-DLY

I

IN-OP

I

IN-SD

CURRENT LIMIT

I

LIM

DIM COMPARATOR

V

IH

V

IL

I

DIM-PU

On-time 1 VIN= 10V, RON= 200 kΩ 2.1 2.75 3.4 µs
On-time 2 VIN= 70V, RON= 200 kΩ 325 415 505 ns

(1)

CS Regulation Threshold CS Decreasing, SW turns on 194 200 206 mV
CS Over-voltage Threshold CS Increasing, SW turns off 300 mV
CS Bias Current CS = 0V 0.1 µA

Shutdown Threshold RON/ SD Increasing 0.3 0.7 1.05 V
Shutdown Hysteresis RON/ SD Decreasing 40 mV

Minimum Off-time CS = 0V 270 ns

VCCRegulated Output 6.4 7 7.4 V
VIN- V

CC

ICC= 5 mA, 6.0V < VIN< 8.0V 300 mV
VCCBypass Threshold VINIncreasing 8.8 V
VCCBypass Hysteresis VINDecreasing 230 mV

VIN= 6V 55
VCCOutput Impedance
(0 mA < ICC< 5 mA)

VIN= 8V 50

VIN= 24V 0.4
VCCCurrent Limit

(1)

VIN= 24V, VCC= 0V 16 mA
VCCUnder-voltage Lock-out Threshold VCCIncreasing 5.3 V
VCCUnder-voltage Lock-out Hysteresis VCCDecreasing 150 mV
VCCUnder-voltage Lock-out Filter Delay 100 mV Overdrive 3 µs
IINOperating Current Non-switching, CS = 0.5V 625 900 µA
IINShutdown Current RON / SD = 0V 95 180 µA

Current Limit Threshold 1.2 1.5 1.8 A

Logic High DIM Increasing 2.2 V
Logic Low DIM Decreasing 0.8 V
DIM Pull-up Current DIM = 1.5V 80 µA

Ω

(1) VCC provides self bias for the internal gate drive and control circuits. Device thermal limitations limit external loading.

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SNVS465F –OCTOBER 2006–REVISED MAY 2013

LM3404/LM3404HV

(1)

(continued)

Symbol Parameter Conditions Min Typ Max Units

MOSFET AND DRIVER

R

DS-ON

V

DR-UVLO

V

DR-HYS

Buck Switch On Resistance ISW= 200mA, BST-SW = 6.3V 0.37 0.75 Ω
BST Under-voltage Lock-out Threshold BST–SW Increasing 1.7 3 4 V
BST Under-voltage Lock-out Hysteresis BST–SW Decreasing 400 mV

THERMAL SHUTDOWN

T

SD

T

SD-HYS

Thermal Shutdown Threshold 165 °C
Thermal Shutdown Hysteresis 25 °C

THERMAL RESISTANCE

θ

JA

Junction to Ambient °C/W

SOIC-8 Package 155

So PowerPAD-8 Package

(2)

50

(2) θJAof 50°C/W with DAP soldered to a minimum of 2 square inches of 1oz. copper on the top or bottom PCB layer.

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SNVS465F –OCTOBER 2006–REVISED MAY 2013

TYPICAL PERFORMANCE CHARACTERISTICS

spacer

V

vs Temperature (VIN= 24V) V

REF

Figure 3. Figure 4.

V

vs VIN, LM3404HV (TA= 25°C) Current Limit vs Temperature (VIN= 24V)

REF

vs VIN, LM3404 (TA= 25°C)

REF

Figure 5. Figure 6.

Current Limi vs VIN, LM3404 (TA= 25°C) Current Limit vs VIN, LM3404HV (TA= 25°C)

Figure 7. Figure 8.

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TYPICAL PERFORMANCE CHARACTERISTICS (continued)

spacer

TONvs VIN, RON= 100 kΩ (TA= 25°C) TONvs VIN, (TA= 25°C)

Figure 9. Figure 10.

TONvs VIN, (TA= 25°C) TONvs RON, LM3404 (TA= 25°C)

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Figure 11. Figure 12.

TONvs RON, LM3404HV (TA= 25°C) VCCvs VIN(TA= 25°C)

Figure 13. Figure 14.

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spacer

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

V

vs fSW, LM3404 (TA= 25°C) V

O-MAX

Figure 15. Figure 16.

V

vs fSW, LM3404HV (TA= 25°C) V

O-MAX

SNVS465F –OCTOBER 2006–REVISED MAY 2013

vs fSW, LM3404 (TA= 25°C)

O-MIN

vs fSW, LM3404HV (TA= 25°C)

O-MIN

Figure 17. Figure 18.

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BOOT

VCC

VIN

SW

CS

DIM

GND

VIN

SENSE

7V BIAS

REGULATOR

BYPASS
SWITCH

VCC

UVLO

THERMAL

SHUTDOWN

ON TIMER

R

ON

Complete

Start

+

-

300 ns MIN

OFF TIMER

Complete
Start

LOGIC

+

-

+

-

+

-

CURRENT
LIMIT OFF

TIMER

BUCK

SWITCH

CURRENT

SENSE

LEVEL

SHIFT

GATE DRIVE

UVLO

VIN

+

-

1.5A

0.7V

0.2V

0.3V

1.5V

5V

75 PA

SD

LM3404, LM3404HV

SNVS465F –OCTOBER 2006–REVISED MAY 2013

BLOCK DIAGRAM

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f

SW

=

V

O

1.34 x 10

-10

x R

ON

VO = n x VF + 200 mV

LM3404/04HV

CS

R

SNS

One-shot

CS

Comparator

V

O

V

F

I

F

LED 1

LED n

+

-

-

+

I

F

V

SNS

V

REF

t

ON

= 1.34 x 10

-10

x

R

ON

V

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SNVS465F –OCTOBER 2006–REVISED MAY 2013

APPLICATION INFORMATION

THEORY OF OPERATION

The LM3404 and LM3404HV are buck regulators with a wide input voltage range, low voltage reference, and a
fast output enable/disable function. These features combine to make them ideal for use as a constant current
source for LEDs with forward currents as high as 1.2A. The controlled on-time (COT) architecture is a
combination of hysteretic mode control and a one-shot on-timer that varies inversely with input voltage.
Hysteretic operation eliminates the need for small-signal control loop compensation. When the converter runs in
continuous conduction mode (CCM) the controlled on-time maintains a constant switching frequency over the
range of input voltage. Fast transient response, PWM dimming, a low power shutdown mode, and simple output
overvoltage protection round out the functions of the LM3404/04HV.

CONTROLLED ON-TIME OVERVIEW

Figure 19 shows the feedback system used to control the current through an array of LEDs. A voltage signal,

V

, is created as the LED current flows through the current setting resistor, R

SNS

to the CS pin, where it is compared against a 200 mV reference, V
MOSFET when V

falls below V

SNS

. The power MOSFET conducts for a controlled on-time, tON, set by an

REF

. The on-comparator turns on the power

REF

external resistor, RON, and by the input voltage, VIN. On-time is governed by the following equation:

At the conclusion of tONthe power MOSFET turns off for a minimum off-time, t
complete the CS comparator compares V

SNS

and V

again, waiting to begin the next cycle.

REF

, to ground. V

SNS

, of 300 ns. Once t

OFF-MIN

is fed back

SNS

OFF-MIN

(1)

is

The LM3404/04HV regulators should be operated in continuous conduction mode (CCM), where inductor current
stays positive throughout the switching cycle. During steady-state CCM operation, the converter maintains a
constant switching frequency that can be selected using the following equation:

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Figure 19. Comparator and One-Shot

• VF= forward voltage of each LED

• n = number of LEDs in series (2)

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T

SW

300 ns

V

O(MIN)

= VIN x

T

SW

TSW - 300 ns

V

O(MAX)

= VIN x

TSW = 1/f

SW

n

MAX

=

V

F(MAX)

V

O(max)

- 200 mV

D

MAX

=

t

ON

t

ON

+ t

OFF-MIN

V

O(max)

= D

MAX

x V

IN

I

L-MIN

=

0.2

R

SNS

L

-

VO x t

SNS

LM3404, LM3404HV

SNVS465F –OCTOBER 2006–REVISED MAY 2013

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AVERAGE LED CURRENT ACCURACY

The COT architecture regulates the valley of ΔV
current (which is also the average inductor current) the valley inductor current is calculated using the following
expression:

In this equation t
average inductor/LED current is equal to I

IF= IL= I

L-MIN

represents the propagation delay of the CS comparator, and is approximately 220 ns. The

SNS

+ ΔiL/ 2 (4)

plus one-half of the inductor current ripple, ΔiL:

L-MIN

Detailed information for the calculation of ΔiLis given in the Design Considerations section.

, the AC portion of V

SNS

. To determine the average LED

SNS

(3)

MAXIMUM OUTPUT VOLTAGE

The 300 ns minimum off-time limits the maximum duty cycle of the converter, D
output voltage, V

The maximum number of LEDs, n
maximum forward voltage of the LEDs used, V

, determined by the following equations:

O(MAX)

, that can be placed in a single series string is governed by V

MAX

F(MAX)

, using the expression:

, and in turn the maximum

MAX

O(MAX)

(5)

and the

(6)

At low switching frequency the maximum duty cycle and output voltage are higher, allowing the LM3404/04HV to
regulate output voltages that are nearly equal to input voltage. The following equation relates switching frequency
to maximum output voltage, and is also shown graphically in the Typical Performance Characteristics section:

(7)

MINIMUM OUTPUT VOLTAGE

The minimum recommended on-time for the LM3404/04HV is 300 ns. This lower limit for tONdetermines the
minimum duty cycle and output voltage that can be regulated based on input voltage and switching frequency.
The relationship is determined by the following equation, shown on the same graphs as maximum output voltage
in the Typical Performance Characteristics section:

(8)

HIGH VOLTAGE BIAS REGULATOR

The LM3404/04HV contains an internal linear regulator with a 7V output, connected between the VIN and the
VCC pins. The VCC pin should be bypassed to the GND pin with a 0.1 µF ceramic capacitor connected as close
as possible to the pins of the IC. VCC tracks VIN until VIN reaches 8.8V (typical) and then regulates at 7V as
VIN increases. Operation begins when VCC crosses 5.25V.

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