LT3755/LT3755-1/LT3755-2

1

Rev. E

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TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

TheLT®3755,LT3755-1andLT3755-2areDC/DCcontrol-

lers designed to operate as a constant-current source for

driving high current LEDs. They drive a low side external

N-channelpowerMOSFETfromaninternalregulated7.15V

supply. The fixed frequency, current mode architecture

results in stable operation over a wide range of supply

and output voltages. A ground referenced voltage FB pin

serves as the input for several LED protection features,

and also makes it possible for the converter to operate

as a constant-voltage source. A frequency adjust pin

allows the user to program the frequency from 100kHz

to 1MHz to optimize efficiency, performance or external

component size.

The LT3755/LT3755-1/LT3755-2 sense output current at

the high side of the LED string. High side current sensing

is the most flexible scheme for driving LEDs, allowing

boost, buck mode or buck-boost mode configuration.

The PWM input provides LED dimming ratios of up to

3000:1, and the CTRL input provides additional analog

dimming capability.

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

by U.S. patents, including 7199560 and 7321203.

50W White Automotive LED Headlamp Driver

n

3000:1 True Color PWM™ Dimming

n

Wide Input Voltage Range: 4.5V to 40V

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Output Voltage Up to 75V

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Constant-Current and Constant-Voltage Regulation

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100mV High Side Current Sense

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Drives LEDs in Boost, Buck Mode, Buck-Boost Mode,

SEPIC or Flyback Topology

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Adjustable Frequency: 100kHz to 1MHz

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Open LED Protection

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Programmable Undervoltage Lockout with Hysteresis

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Improved Open LED Status Pin (LT3755-2)

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Frequency Synchronization (LT3755-1)

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PWM Disconnect Switch Driver

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CTRL Pin Provides Analog Dimming

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Low Shutdown Current: <1µA

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Programmable Soft-Start

n

Thermally Enhanced 16-Lead QFN (3mm × 3mm)

and MSOP Packages

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AEC-Q100 Qualified For Automotive Applications

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High Power LED

n

Battery Chargers

n

Accurate Current Limited Voltage Regulators

LT3755-2

22µH

GND

SHDN/UVLO

FB

ISP

332k

100k

1M

4.7µF

0.001µF

0.01µF

8V TO

40V

185k

10k

28.7k

375kHz

4.7µF

40.2k

CTRL

0.015

0.1

1M

23.7k

1A

4.7µF

50W

LED

STRING

37551 TA01a

OPENLED

PWM

SS

RT

ISN

GATE

SENSE

PWMOUT

0

10

80

84

88

92

96

100

20

30

40

37551 TA01b