LT3950

1

Rev. 0

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TYPICAL APPLICATION

FEATURES

DESCRIPTION

60V, 1.5A LED Driver with Internal

Exponential Scale Dimming

The LT®3950 is a multitopology DC/DC converter designed

specifically to drive high current LEDs. It contains a 1.5A,

60V DMOS switch and supports an external PWM dim-

ming PMOS. The LT3950 has an internal PWM generator

for dimming that maps an analog control signal to an

exponential scale used to define PWM dimming duty ratio.

Using an exponential scale to define duty ratio preserves

dimming resolution across a wide range of LED current.

In addition to operating as a constant current source, the

LT3950 also provides output voltage regulation. This can

be used to prevent damage to the part in case of open LED

events. A programmable switching frequency offers flex-

ibility in design for higher efficiency or reduced compo-

nent size. Enabling spread spectrum frequency modula-

tion reduces EMI. The switching frequency can also easily

be synchronized by driving the SYNC/SPRD pin with an

external clock. LED current is programmed with a single

external sense resistor and can be adjusted from zero to

full-scale by an analog signal at the CTRL pin.

10W LED Driver for Automotive, 2MHz, 90% Efficient

Efficiency and Power Loss with

and without PWM Dimming

APPLICATIONS

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Operates in Boost, SEPIC, Buck Mode and Buck-

Boost Mode

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128:1 Internal Exponential Scale PWM Dimming

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Wide Input Voltage Range (3V to 60V)

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1.5A, 60V Internal Switch

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20000:1 External PWM Dimming at 100Hz

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±2% LED Current and Output Voltage Regulation

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PMOS Switch Driver for PWM Dimming

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LED Short/Open Protection and Indication

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Constant Voltage and Constant Current Regulation

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Adjustable 300kHz to 2MHz Switching Frequency

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Adjustable 100Hz to 1kHz PWM Generator Frequency

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Internal Spread Spectrum Frequency Modulation

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Easy Synchronization to External Clock

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Available in 16-Lead MSOP Package

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Display Backlighting

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Automotive and Avionic Lighting

All registered trademarks and trademarks are the property of their respective owners. Protected

by U.S. Patents, including 7199560, 7321203, 7746300, 8116045. Patents pending.

LT3950

3950 TA01a

2.2µF

1M

24.9k

FB

PWMTG

VC

PWM

CTRL

ISP

ISN

SW

1µF

220pF

2.2µF

10W

LED

POWER

(DERATED

BELOW

267k

39k

FAULT

FAULT

EN/UVLO

3V TO16V DC

TRANSIENT

TO 48V

100k

100k

SYNC/SPRD RP

RT

GND

300Hz

182k

2MHz

45.3k

10µH

1

EFFICIENCY 100% ON

EFFICIENCY (EFF.) AT

10% PWM DIMMING

10 13 16 19 22 25 28 31 34 37 40

60

64

68

72

76

80

84

88

92

96

100

0.500

0.750

1.000

1.250

1.500

1.750

2.000

2.250

2.500

2.750

3.000

3950 TA01b