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HIGH-EFFICIENCY CURRENT SOURCE DRIVES WHITE LEDs FOR BACKLIT DISPLAYS
SUNNYVALE, CA—February 28, 2000—Maxim Integrated Products introduces the MAX1698, a switch-mode step-up controller that regulates LED current at power levels up to 5W. The MAX1698 is the most efficient driver for chains of white or color LEDs used in backlit displays for PDAs, digital cameras, and laptop computers. White LEDs and the MAX1698 offer greater simplicity, lower cost, higher efficiency, longer bulb life, and greater reliability than displays using fluorescent (CCFL) and electroluminescent (EL) lamps.
The MAX1698 can operate with more than 90% efficiency. Losses are minimized by a low, 300mV current-sense threshold. A sense resistor of typically 15 ohms sets the current through the primary chain of LEDs. Additional chains of matching LEDs can be added with an equivalent resistor to closely match the primary chain. LED current control and dimming are accomplished using the adjust pin rather than high-value current-limiting resistors, which dissipate power and decrease efficiency. The MAX1698 also features a soft-start circuit that eliminates input current surges at turn-on.
The MAX1698EUB comes in a very small 10-pin µMAX package, only 1.09mm high and half the area of an 8-pin SO. The part is guaranteed for the extended-industrial temperature range (-40°C to +85°C). Prices start from $1.40 (1000-up, FOB USA). A fully assembled evaluation kit (MAX1698EVKIT) is available to help speed designs.
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