High-current Ssld Provides Adjustable Over-voltage Protection For Single Or Dual Leds In Handheld Devices

摘要

National Semiconductor introduced a high-current SSLD that enables dual LED operation for the camera flash function in portable multimedia devices. The LM3553 fixed-frequency, step-up DC/DC converter with two regulated current sinks drives loads up to 1.2 A from a single-cell Li-Ion battery. The driver's adjustable over-voltage protection circuitry allows designers to drive two high-current LEDs in a series configuration, which maximizes the illumination-to-power ratio. The LM3553 can drive the camera in a high-power flash mode for still photography or a low-power torch mode for video record- ing. To configure the driver to fit their application, designers can use the adjustable 128-flash current levels and 16-flash timer durations via an I~2C compatible interface. The LM3553 also features built-in time-out protection for the flash LEDs in case of an error condition. The flash LED driver maximizes the light output for low-power systems, with peak efficiency equal to or greater than 90 percent.