LM3405

550kHz/1.6MHz 1A Constant Current Buck Regulator for

Powering LEDs

General Description

Integrated with a 1A power switch, the LM3405 is a current

mode control switching buck regulator designed to provide a

simple, high efficiency solution for driving LEDs. With a 0.2V

reference voltage feedback control to minimize power dissi-

pation, an external resistor sets the current as needed for

driving various types of LEDs. Switching frequency is inter-

nally set to 550kHz (LM3405-Y) or 1.6MHz (LM3405-X),

allowing small surface mount inductors and capacitors to be

used. The LM3405 utilizes current mode control and internal

compensation offering ease of use and predictable, high

performance regulation over a wide range of operating con-

ditions. Additional features include user accessible enable/

dim pin for enabling and PWM dimming of LEDs, thermal

shutdown, current limit and over voltage protection.

Features

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Thin SOT23-6 package

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4.0V to 20V input voltage range

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550kHz (LM3405Y) and 1.6MHz (LM3405X)

switching frequencies

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300m

Ω NMOS switch

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30nA shutdown current

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Enable/DIM input for enabling and PWM dimming of

LEDs

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Requires only low value, ceramic capacitors

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Input voltage UVLO

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Internally compensated current mode control

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Thermal shutdown

Applications

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LED Driver

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Constant Current Source

Typical Application Circuit

20178901

Connection Diagrams

20178905

6-Lead TSOT

NS Package Number MK06A

20178960

Pin 1 Indentification

ADVANCE INFORMATION

October 2006

© 2006 National Semiconductor Corporation

DS201789

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