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Optoelectronics/Displays??

LEDs support local-dimming LCD backlights

Posted: 11 Dec 2007 ?? ?Print Version ?Bookmark and Share

Keywords:LED driver? local dimming? LED-based LCD backlight technology? optimized synchronization?

austriamicrosystems has launched high-precision LED drivers with optimal support for local-dimming LCD backlight technology. The AS3693 and AS3694 are suitable for LED-based LCD backlighting applications in large LCD TVs, PC monitors and laptops.

They feature optimized synchronization and timing technologies, avoiding costly and suboptimal designs based on standard LED drivers. They meet the latest trend in LCD backlighting, which is to synchronize the LCD backlight with the TV picture. So-called local dimming enables only the required segments of the backlight to be on, making bright spots in the TV picture appear really bright and dark parts completely black. This technology allows OEMs to achieve exceptional contrast ratios as well as energy savings.

The new AS3693 and AS3694 LED drivers also offer outstanding driver accuracy of 0.5 percent which guarantees exact brightness and color matching and is ahead of any competitor device currently available on the market. AS3693 offers 16 high brightness LED output channels; AS3694 provides 12 channels and 3 additional DC/DC converters. The brightness and timing of each output can be controlled individually via SPI or I?C. Local dimming is supported by independent PWM generators with programmable delay, period and duty cycle, resulting in optimized TV pictures which are totally flicker-free.

The AS3693 and AS3694 high precision LED current sources have a wide voltage compliance range of 50V supporting the deployment of long LED strings. In addition, an integrated dedicated power supply control technology enables thermal and energy efficient design. The supply voltage for the AS3693 and AS3694 is derived from the LED supply voltage via the build-in shunt regulator. Both devices offer safety features for thermal control as well as open and short LED detection.

Markus Luidolt, Marketing Manager Backlighting at austriamicrosystems, stated, "Our innovative AS3693/94 LED drivers are gaining acceptance among major LCD panel and LCD TV manufacturers with very positive feedback from OEMs after initial tests. austriamicrosystems' high precision LED drivers fit 100 percent with the latest LCD backlight technologies like local dimmingno matter if RGB or white LEDs."

The AS3693 and AS3694 are available in a TQFP64 package and are specified for -20 to +85C ambient temperature. Product-specific information and free samples are available.




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