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Optoelectronics/Displays??

Boost converter drives up to 10 LEDs

Posted: 23 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Catalyst? LED driver? CAT4238?

Catalyst Semiconductor Inc. announced it has expanded its family of LED drivers with the addition of CAT4238, a high-voltage boost converter designed to drive up to 10 LEDs. According to the company, the device uses a low-noise, high-frequency switching scheme and contains fully integrated features, which eliminate the need for external components associated with soft-start and over-voltage protection. This helps designers reduce noise and save board space in mid- to large-size LCD panel backlighting applications. 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. Catalyst said the new device uses a fixed frequency (1MHz) switching architecture, making it suitable for low noise applications. 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 up to 87 percent, explained the company.

To eliminate excessive "in-rush" currents that can occur during initial power-up, the device has an integrated soft-start control. In the event of an open-LED fault condition, an internal over-voltage 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, eliminating the need for external components and the associated cost and board space overhead.

CAT4238 is available in a low-profile (1mm max height), RoHS-compliant 5-lead thin SOT23 package. Pricing for 10,000 piece quantities is 78 cents each. Samples and evaluation kits are available. Projected lead-times for production quantities are currently 6 to 8 weeks ARO.




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