October 2006 LM3405 550kHz/1.6MHz 1A Constant Current Buck Regulator for Powering LEDs General Description Features 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 dissipation, an external resistor sets the current as needed for driving various types of LEDs. Switching frequency is internally 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 conditions. Additional features include user accessible enable/ dim pin for enabling and PWM dimming of LEDs, thermal shutdown, current limit and over voltage protection. n Thin SOT23-6 package n 4.0V to 20V input voltage range n 550kHz (LM3405Y) and 1.6MHz (LM3405X) switching frequencies n 300mΩ NMOS switch n 30nA shutdown current n Enable/DIM input for enabling and PWM dimming of LEDs n Requires only low value, ceramic capacitors n Input voltage UVLO n Internally compensated current mode control n Thermal shutdown Applications n LED Driver n Constant Current Source Typical Application Circuit 20178901 Connection Diagrams 20178905 6-Lead TSOT NS Package Number MK06A © 2006 National Semiconductor Corporation DS201789 20178960 Pin 1 Indentification www.national.com LM3405 500kHz/1.6MHz 1A Constant Current Buck Regulator for Powering LEDs ADVANCE INFORMATION LM3405 500kHz/1.6MHz 1A Constant Current Buck Regulator for Powering LEDs Physical Dimensions inches (millimeters) unless otherwise noted 6-Lead TSOT Package NS Package Number MK06A National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. BANNED SUBSTANCE COMPLIANCE National Semiconductor follows the provisions of the Product Stewardship Guide for Customers (CSP-9-111C2) and Banned Substances and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at: www.national.com/quality/green. Lead free products are RoHS compliant. National Semiconductor Americas Customer Support Center Email: [email protected] Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: [email protected] National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: [email protected] Tel: 81-3-5639-7560