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DC/DC converter operates as constant-current LED driver

Posted: 05 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Linear? LT3475? DC/DC converter? step-down? dual?

Linear Technology Corp. 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. The company said 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 out-of-phase with the other, Linear said, reducing input ripple. Output current accuracy is independently maintained for each channel over a 50mA to 1.5A range, while True Color PWM circuitry allows a dimming range of 3000:1 without any of the color shift typically associated with LED current dimming, the company added.

With its input voltage range of 4V to 36V (transients up to 40V), the device 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, said LInear. 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, the device offers a compact solution for driving high current LEDs, Linear said. It utilizes a high side sense, enabling a grounded LED cathode connection, eliminating the need for an LED return wire in most applications. The device also has an integrated boost diode for each channel, said the company, further reducing the solution footprint and cost. Additional features include both open LED and short circuit protection.

The LT3475EFE is available from stock at prices 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.

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