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LED driver lights up your photos

Posted: 19 Nov 2007 ?? ?Print Version ?Bookmark and Share

Keywords:LED driver? mid-size LCD panel? boost converter? digital photo frames?

A LED driver aimed at mid-size LCD panel applications has been introduced by Catalyst Semiconductor Inc. The CAT4139 is a DC/DC boost converter that provides switch current up to 750mA and drives LED strings up to 22V, making it suitable for digital photo frames and other backlighting applications where high LED countsup to 40 LEDsare used.

Many high-voltage boost converters typically use a simple variable-frequency switching scheme, said Catalyst, however, the CAT4139 uses a fixed frequency (1MHz) switching architecture making it suitable for low noise applications. A high voltage CMOS output stage in the device allows five LED strings (up to 22V) 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 which can occur during initial power-up, the CAT4139 offers 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 integrated, eliminating the need for external components and the associated cost and board space overhead, said Catalyst.

LED dimming can be controlled using a DC voltage, logic signal, or PWM signal. The device is packaged in a 5-lead TSOT23 (1mm max height).

- Gina Roos

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