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LM3407

www.ti.com

SNVS553B –JANUARY 2008–REVISED MAY 2013

350 mA, Constant Current Output Floating Buck Switching Converter for High Power

LEDs

Check for Samples: LM3407

FEATURES

DESCRIPTION

The LM3407 is a constant current output floating

• Input operating range 4.5V to 30V

buck switching converter designed to provide

• Output voltage range: 0.1V

to 0.9V

constant current to high power LEDs. The device is

• Accurate constant current output

ideal for automotive, industrial and general lighting

applications. The LM3407 has an integrated power N-

• Independent device enable (CMOS compatible)

MOSFET that makes the application solution compact

and PWM dimming control

and simple to implement. An external 1% thick-film

• Converter switching frequency adjustable from

resistor allows the converter output voltage to adjust

300 kHz to 1 MHz

as needed to deliver constant current within 10%

• No external control loop compensation

accuracy to a serially connected LED string of varying

number and type. Converter switching frequency is

required

adjustable from 300 kHz to 1 MHz. The LM3407

• Supports ceramic and low ESR output

features a dimming input to enable LED brightness

capacitors

control by Pulse Width Modulation (PWM).

• Input Under Voltage Lock Out (UVLO)

Additionally, a separate enable pin allows for low

power shutdown. An exposed pad MSOP-8

• Thermal shutdown protection

PowerPAD package provides excellent heat

• MSOP-8 PowerPAD Package

dissipation and thermal performance. Input UVLO

and output open-circuit protection ensure a robust

APPLICATIONS

LED driver solution.

• LED Driver

• Constant Current Source

• Automotive Lighting

• General Illumination

• Industrial Lighting

TYPICAL APPLICATION

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.

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.

Summary of content (22 pages)

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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 350 mA, Constant Current Output Floating Buck Switching Converter for High Power LEDs Check for Samples: LM3407 FEATURES DESCRIPTION • • • • The LM3407 is a constant current output floating buck switching converter designed to provide constant current to high power LEDs. The device is ideal for automotive, industrial and general lighting applications.
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LM3407 SNVS553B – JANUARY 2008 – REVISED MAY 2013 www.ti.com CONNECTION DIAGRAM Top View 8 1 ISNS LX DIM GND EN VCC 2 7 3 6 EP 4 5 FS VIN Figure 1. 8-Lead Plastic MSOP-8 PowerPAD Package See Package Number DGN0008A PIN DESCRIPTIONS 2 Pin Name Description 1 ISNS LED Current Sense pin Connect resistor RISNS from this pin to ground for LED current sensing. The current sensing resistor should be placed close to this pin.
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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 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 (1) If Military/Aerospace specified devices are required, contact the Texas Instruments Sales Office/Distributors for availability and specifications. VALUE / UNIT VIN to GND -0.
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LM3407 SNVS553B – JANUARY 2008 – REVISED MAY 2013 www.ti.com ELECTRICAL CHARACTERISTICS VIN = 12V unless otherwise indicated. Typical and limits appearing in plain type apply for TA = TJ = 25°C (Note 4). Limits appearing in boldface type apply over full Operating Temperature Range. Datasheet min/max specification limits are specified by design, test, or statistical analysis. Parameter Test Conditions Min Typ Max Units 0.58 0.78 0.98 mA 0.20 0.27 0.
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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS Unless otherwise specified, all curves shown are taken in typical application at VIN = 12V, TA = 25°C, and ILED = 350 mA (driving two power LEDs). Output Current vs Input Voltage (TA = -40°C) Output Current vs Input Voltage (TA = 25°C) Figure 2. Figure 3. Output Current vs Input Voltage (TA = 125°C) Efficiency vs Input Voltage (TA = -40°C) Figure 4. Figure 5.
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LM3407 SNVS553B – JANUARY 2008 – REVISED MAY 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified, all curves shown are taken in typical application at VIN = 12V, TA = 25°C, and ILED = 350 mA (driving two power LEDs). 6 Switch On Time vs Input Voltage Operating Input Current vs Input Voltage Figure 8. Figure 9. VCC Voltage vs Input Voltage Output Current vs RISNS Figure 10. Figure 11.
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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified, all curves shown are taken in typical application at VIN = 12V, TA = 25°C, and ILED = 350 mA (driving two power LEDs). Continuous Mode Operation (VIN = 12V, L = 33µH, fSW = 500kHz) Continuous Mode Operation (VIN = 24V, L = 33µH, fSW = 1MHz) Figure 14. Figure 15.
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LM3407 SNVS553B – JANUARY 2008 – REVISED MAY 2013 www.ti.com SIMPLIFIED FUNCTIONAL BLOCK DIAGRAM FS VIN VIN VCC regulator Clock Generator + 3.6V - VCC VCC LX SD UVLO 6 DIM Set DIM SWITCH CONTROL Slope Compensation DIM + - 400 k: ISNS Reset PWM Comparator 3.6V EA gm 3.
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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 The operation of the LM3407 constant current output floating buck converter is explained below. With the internal switch Q1 turned ON, current flows through the inductor L1 and the LED array. Energy is also stored in the magnetic field of the inductor during the ON cycle. The current flowing through RISNS during the ON cycle is monitored by the Average Current Sensing block.
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LM3407 SNVS553B – JANUARY 2008 – REVISED MAY 2013 IL1 www.ti.com IOUT = IL1(AVG) IOUT time ILX time VISNS VMSL time VRP VREF time tON tOFF T Figure 20. LM3407 Switching Waveforms The switching frequency and duty ratio of the converter equal: tON D= tON + tOFF and fSW = 1 tON + tOFF (1) By comparing the area of VISNS and VRP over the ON period, an error signal is generated.
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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 VISNS1 VMSL 0 VPWM 0 VISNS2 VMSL 0 Figure 21. Pulse-Level Transformation When VMSL is higher than VREF, the peak value of VRP, the switching duty cycle of the power switch will be reduced to lower VMSL. When VMSL is lower than the peak value of VRP, the switching duty cycle of the power switch will be increased to raise VMSL. For example, when IOUT is decreased, VMSL will become lower than VREF.
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LM3407 SNVS553B – JANUARY 2008 – REVISED MAY 2013 www.ti.com T tON VRP IOUT * RISNS 0 VISNS VMSL < VREF VMSL = VREF Figure 23. Waveforms of VISNS and VRP Under Closed Loop Operation INTERNAL VCC REGULATOR The LM3407 has an internal 4.5V linear regulator. This regulated voltage is used for powering the internal circuitry only and any external loading at the VCC pin is not recommended. The supply input (VIN) can be connected directly to an input voltage up to 30V.
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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 APPLICATION INFORMATION SWITCHING FREQUENCY SELECTION The selection of switching frequency is based on the consideration of the conversion efficiency, size of the passive components, and the total solution cost. In general, increasing the switching frequency will allow the use of smaller external components but will decrease the conversion efficiency.
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LM3407 SNVS553B – JANUARY 2008 – REVISED MAY 2013 www.ti.com SELECTION OF INDUCTOR In order to achieve accurate constant current output, the LM3407 is required to operate in Continuous Conduction Mode (CCM) under all operating conditions. In general, the magnitude of the inductor ripple current should be kept as small as possible. If the PCB size is not limited, higher inductance values result in better accuracy of the output current.
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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 Table 1. Suggested Inductance Value of the Inductor VIN / V Number of LED 1 2 3 4 5 6 7 Inductor selection table for FSW = 500 kHz, COUT = 4.7µF (1µF for 1 LED) 5 22 µH 10 22 µH 22 µH 15 22 µH 22 µH 22 µH 20 22 µH 33 µH 22 µH 22 µH 22 µH 25 22 µH 33 µH 33 µH 22 µH 22 µH 22 µH 30 22 µH 47 µH 33 µH 33 µH 33 µH 22 µH 22 µH Inductor selection table for FSW = 1 MHz, COUT = 4.
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LM3407 SNVS553B – JANUARY 2008 – REVISED MAY 2013 www.ti.com Figure 25. Typical Application Schematic for 6 LEDs Figure 26.
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LM3407 www.ti.com SNVS553B – JANUARY 2008 – REVISED MAY 2013 REVISION HISTORY Changes from Revision A (May 2013) to Revision B • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM3407MY/NOPB MSOPPower PAD DGN 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1 LM3407MYX/NOPB MSOPPower PAD DGN 8 3500 330.0 12.4 5.3 3.4 1.4 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM3407MY/NOPB MSOP-PowerPAD DGN 8 1000 210.0 185.0 35.0 LM3407MYX/NOPB MSOP-PowerPAD DGN 8 3500 367.0 367.0 35.
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MECHANICAL DATA DGN0008A MUY08A (Rev A) BOTTOM VIEW www.ti.
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