White LED Driver – targets low voltage applications

Catalyst Semiconductor has expanded its family of white LED products with the introduction of an inductor-based white LED driver boost converter. Designed for colour LCD and keypad backlighting applications, the CAT37 delivers a regulated output current at a constant switching frequency of 1.2MHz, enabling the device to be used with very small value external inductor and ceramic capacitors. Optimised to drive up to four white LEDs, the CAT37 is over 80% power efficient and features a shutdown current of less than 1A, ensuring optimal battery run time in hand-held applications. At the same time its low 2.5V input voltage operation makes it ideal for use in devices powered by single-cell Li-Ion and multi-cell Alkaline/NiMH batteries. Additional features of the device include low quiescent ground current (0.5mA typ), adjustable output current (up to 40mA) and a low resistance (0.5 Ohm) power switch. The CAT37 delivers a constant current to series-connected LEDs, ensuring uniform brightness regardless of variations in the LED's forward voltage drops. Its high accuracy feedback voltage (regulated at 95mV) ensures high frequency and provides reliable brightness control even when partially dimmed to current levels of between 6 to 8mA. The CAT37 can also safely withstand an open output circuit. High efficiency and low noise, combined with its low profile 5-lead packages makes the CAT37 the ideal device to drive up to four white LEDs in almost any handheld application, typically mobile phones, digital cameras, PDAs, portable MP3 players, handheld terminals and digital cameras. Four white LED configurations are also used to backlight automotive and aircraft instrumentation and in photographic flash equipment. The CAT37 White LED Driver Boost Converter is available in low profile 5-lead SOT23 and thin TDFN halogen and lead free “green” packages. Catalyst Semiconductor Inc, Sunnyvale, CA 94089, USA.

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