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LED drivers for backlights extend mobile battery life

Posted: 11 Feb 2008 ?? ?Print Version ?Bookmark and Share

Keywords:LED driver? current regulator? interface?

Leadis Technology Inc. has started sampling a new family of charge-pump-based LED drivers that uses the company's PowerLite current regulator to deliver up to 95 percent power efficiency for longer battery life.

Targeted at mobile backlighting applications, the LDS8867, LDS8868 and LDS8869 support up to six LEDs with a maximum current of 32mA per channel. The new 1-wire interface products join the previously announced PWM interface products to give mobile phone design engineers more flexibility with a new set of performance/interface choices.

In addition, the company's low voltage dropout PowerLite current regulator provides a typical transition threshold of only 50mV, allowing a device to stay in a charge-pump driver's highest-efficiency mode longer than competing products. The technique also solves one of the most significant problems associated with charge-pump based LED drivers, namely the transition between the high-efficiency state (1x-mode) and the lower efficiency states. By lowering the drop out voltage of the driver to only 50mV, battery life can be extended by up to 20 percent.

The LDS8867, LDS8868 and LDS8869 are high-efficiency multimode fractional charge pump with ultra low dropout voltage that can drive up to six LEDs. The addition of a 1.33x fractional charge pump mode and PowerLite current regulator increase the efficiency up to 95 percent. The 1.33x mode requires no additional external capacitors. Its EN/SET logic input functions as a chip enabler and LED current control.

"Leadis is committed to making mobile phones more efficient as they evolve to deliver not only voice data but many other multimedia features such as internet, digital photo stills and videos, GPS, as well as cell phone gaming," said Adolfo Garcia, senior director of LED drivers at Leadis. "As these portable applications continue to proliferate, optimizing the LED driver's efficiency becomes essential. Leadis LED drivers will continue to address and improve on the most important requirement in these mobile appliances: longer battery life."

Maximum LED current of 32mA and can be programmed from 0.5mA to 32mA in 0.5mA increments. The multifractional charge pump supports a wide range of input voltages from 2.7V to 5.5V. The devices are available in a 16-lead TQFN 3mm x 3mm package with a maximum height of 0.8mm.

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