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2W LED driver delivers high voltage, switch current

Posted: 14 Jun 2007 ?? ?Print Version ?Bookmark and Share

Keywords:2W LED driver? LED driver? backlighting? LEDs?

CAT4240 LED driver from Catalyst Semiconductor

Catalyst Semiconductor Inc. launched a 2W LED driver to address high-power backlighting applications. The CAT4240 boost converter provides a high switch current up to 750mA and high voltage up to 38V, making it ideal for driving a wide range of backlighting applications ranging from 1W LEDs in series to multiple strings of lower-power LEDs.

The CAT4240 provides 2W of output power from a 3V to 5V supply and up to 6W when configured with a higher voltage, split supply of 9-12V. The device is also designed with a low-noise, high-frequency switching scheme and contains fully integrated features, which eliminates the need for external components associated with soft-start and overvoltage protection, reducing noise and saving board space.

Many high-voltage boost converters typically use a simple variable-frequency switching scheme. This approach results in a wide range of unwanted harmonics, which are not easy to filter or eliminate. CAT4240 uses a fixed frequency (1MHz) switching architecture making it suited for low noise apps. A high voltage CMOS output stage in the device allows large LED strings (up to 38V) to be accurately biased and regulated from a low voltage input supply while still delivering efficiency levels of up to 87 percent.

To eliminate excessive "in-rush" currents that can occur during initial power-up, the CAT4240 offers an integrated soft-start control. When an open-LED fault condition occurs, an internal overvoltage protection circuit will place the device into a low-power operating mode, restricting the output voltage to safe levels without the need for external circuitry. Both of these features are fully integrated..

Designers have a choice of controlling LED dimming in the CAT4240 using a DC voltage, logic signal or PWM signal.

The CAT4240 LED driver is housed in 5-lead SOT23 (1mm max height) package and is priced at 84 cents each in 10,000-piece quantities. Samples are available now. Projected lead-time for production quantities is currently 6 to 8 weeks ARO.

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