Dual 36V Step-Down LED Driver Delivers up to 1.5A/Channel and Offers 3000:1 True Color PWM Dimming

Jan. 5, 2007
Date Announced: 05 Jan 2007 Linear Technology has announced the LT3475, a dual 36V, up to 2MHz step-down DC/DC converter designed to operate as a two-channel constant- current LED driver. Each channel has an internal sense resistor and dimming control, making it ideal for driving LEDs requiring up to 1.5A of current. One channel switches 180 degrees out-of-phase with the other, reducing input ripple. High output current accuracy is independently maintained for each channel over a wide range of 50mA to 1.5A,while unique True Color PWM™ circuitry allows a dimming range of 3000:1 without any of the color shift typically associated with LED current dimming. With its wide input voltage range of 4V to 36V (transients up to 40V), the LT3475 regulates a broad array of power sources, from 2-cell Li-Ion batteries and 5V logic rails to unregulated wall transformers and automotive power systems. Its switching frequency can be set with a single resistor from 200kHz to 2MHz, enabling the use of tiny inductors and ceramic capacitors. Delivered in a thermally enhanced TSSOP-20 package, it offers a very compact solution for driving high current LEDs.The LT3475 utilizes a high side sense, enabling a grounded LED cathode connection, eliminating the requirement for an LED return wire in most applications. It also has an integrated boost diode for each channel, further reducing the solution footprint and cost. Additional features include both open LED and short circuit protection.Available from stock in a thermally enhanced 20-lead TSSOP package, the LT3475EFE is priced starting at $3.50 each in 1,000-piece quantities. An "I" Grade version, the LT3475IFE is also available from stock, with 1,000-piece pricing starting at $4.20 each.Summary of Features of the LT3475EFE:· True Color PWM Delivers Constant Color with 3000:1 Dimming Range· Wide Input Range: 4V to 36V Operating, 40V Maximum· Accurate and Adjustable Control of LED Current from 50mA to 1.5A· High Side Current Sense Allows Grounded Cathode LED Operation· Accurate and Adjustable 200kHz to 2MHz Switching Frequency· Anti-Phase Switching Reduces Ripple· Uses Small Inductors and Ceramic Capacitors· Available in the Compact 20-Lead TSSOP Thermally Enhanced Surface Mount Package

UK, Ireland, South Africa and Israel: Alastair Boyd, Linear Technology (UK) Limited Tel: +44 (0)1628 477066 E-mail: [email protected] North America and General Information: Doug Dickinson, Linear Technology Corporation Tel: (408) 432 1900 ext. 2233 E-mail: [email protected]

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