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Optoelectronics/Displays??

Four-channel LED driver ensures uniform brightness

Posted: 10 Jun 2009 ?? ?Print Version ?Bookmark and Share

Keywords:LED? LCD? backlighting? processor?

From Exar Corp. comes the XRP7620, a 4-channel, I?C-controlled LED driver with independent software adjustable channel current control.

The XRP7620 is optimized for color mixing applications where a combination of 4 four LEDs is used to generate either a true white light or expand the color spectrum generated when classic RGB three LEDs are combined with a fourth respectively white or amber LED. Four independently adjustable current sinks provide total and precise control of each channel allowing an exact setting of each LED's brightness. The XRP7620 interfaces seamlessly with processor-based designs providing unprecedented ease of use through a standard I?C bus while reducing the number of external components to a single capacitor.

The device is also particularly suitable for small to medium size LCD backlighting applications with a better than 3 percent channel to channel matching ensuring a uniform display brightness. Parallel implementation of several devices on the same I?C bus is possible in order to drive and control larger banks of LEDs for larger size LCD displays.

"Visual indicators and improved display readability requirements are becoming more prevalent in portable and handheld devices to maximize the user experience," said Eric Pittana, director of marketing for Exar's power management product line. "The XRP7620 enables designers to achieve true white light for improved screen resolution or any color of light by means of simple software settings. The XRP7620 represents true creativity and customization at your finger tips."

With 4 independently adjustable current sink drivers, the XRP7620 is a very versatile LED driver as well as a generic software programmable current sink I/O expander. Operating from a single cell Li-ion battery or fixed 3.3V or 5V rails and supporting an industry standard 2-line I?C serial interface, each channel can be programmed up to a current of 31.5mA in steps of 500?A. Selective channel enabling and diming as well as overall configuration is achieved through a set of 5 internal registers. A specific shutdown mode allows the device to retain the previously loaded onfigurationoperational and current programmingin order to be reused again when needed.

Samples of the XRP7620 are available now. Offered in a small 2mm x 3mm 8-pin DFN green/halogen free package operating over the -40C to +100C junction temperature range, the XRP7620 is priced at $0.59 in 1K piece quantities.





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