Santa clara, calif. - ICs capable of driving white-light-emitting diodes are on the move. The chips, stimulated by an unexpectedly swift migration from monochrome to color displays in handheld electronic products, are riding an upsurge in demand. Driver ICs from National Semiconductor Corp. here and Texas Instruments Inc. (Dallas) are among the latest market entrants. National recently added six driver ICs, including two constant-current and two constant-voltage devices, plus two magnetic-boost converters. TI has launched a new constant-current white-LED dri- ver and a liquid-crystal display boost converter. Linear Technology Corp. (Milpitas, Calif.) plans to introduce a new boost converter early in April. Driving white LEDs is considerably more challenging than driving the green LEDs used in monochrome displays, IC vendors say. "The green LEDs that are widely used in monochrome displays have a significantly lower forward voltage than do white LEDs," said Peter Henry, vice president of the portable-power systems group at National. "Monochrome displays typically light up, then turn off, which prolongs battery life, and they are easier to read in ambient light." With white LEDs, he said, "providing uniform brightness is veryimportant."
展开▼
