36V Step-Down LED Driver Delivers up to 1A with True Color PWM Dimming

Oct 19 2005 -MILPITAS, CA
  • Linear Technology announces the LT3474, a 36V, 2MHz step-down DC/DC converter designed to operate as a constant current LED driver. An internal sense resistor and dimming control make it ideal for driving LEDs, which require up to 1A of current. High output current accuracy is maintained over a wide current range of 35mA to 1A. Unique True Color PWM circuitry allows a dimming range of 400:1 without any color shift normally associated with LED current dimming. With its wide input voltage range of 4V to 36V, the LT3474 regulates a broad array of power sources, from 4-cell alkaline/NiCd/NiMH batteries and 5V logic rails to unregulated wall transformers and automotive power systems. Its switching frequency can be set from 200kHz to 2MHz, enabling the use of tiny inductors and ceramic capacitors. Combined with a thermally enhanced TSSOP-16 package, it offers a very compact solution for driving high current LEDs.

    The LT3474 utilizes a high side sense, enabling a grounded LED cathode connection, eliminating the requirement for a grounding wire in most applications. It also has an integrated boost diode, further reducing the solution footprint and cost. Additional features include both open LED and short circuit protection.

    The LT3474EFE is available from stock in a thermally enhanced 16-Lead TSSOP package with 1,000-piece pricing starting at $2.95 each. An "I" Grade version, the LT3474IFE, is also available from stock. Its 1,000-piece pricing starts at $3.54 each.

    Summary of Features: LT3474EFE

    • True Color PWM Delivers Constant Color with 400:1 Dimming Range
    • Wide Input Range: 4V to 36V
    • Up to 1A LED Current
    • Adjustable 200kHz-2MHz Switching Frequency
    • Adjustable Control of LED Current
    • Integrated Boost Diode
    • High Output Current Accuracy is Maintained Over a Wide Range from 35mA to 1A
    • Open LED and Short-Circuit Protection
    • High Side Sense Allows Grounded Cathode Connection
    • Uses Small Inductors and Ceramic Capacitors
    • Compact 16-Lead TSSOP Thermally Enhanced Surface Mount Package


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