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Dc-dc converter drives up to 16 white LEDs with constant current

Posted: 30 Aug 2005 ?? ?Print Version ?Bookmark and Share

Keywords:linear technology? dc-dc converter? lt3486?

Linear Technology Corp. unveiled a dual step-up dc-dc converter designed to drive up to 16 white LEDs (eight LEDs in series per channel) with constant current.

True PWM dimming delivers constant current to the LEDs, keeping the emitted light at a constant color. Dimming is controlled with the duty cycle of the PWM driver, allowing a wide 1,000:1 dimming range.

The company added that the LT3486's high efficiency, current mode and fixed frequency operation ensures uniform LED brightness, low noise and maximum battery life. Its two independent converters are capable of driving asymmetric LED strings (up to eight in a series per converter) from an input voltage of 2.5V to 24V, delivering efficiencies up to 85 percent. Its 5-by-3mm DFN package and tiny externals provide a compact footprint for space-constrained handheld applications, while its 2.5V to 24V input voltage range enables it to operate in applications from Li-ion powered handheld devices to automotive backlighting applications.

The LT3486's switching frequency can be set between 200kHz and 2MHz via a single resistor. According to Linear Tech, this enables the designer to minimize solution footprint and maximize efficiency. Since the LT3486 utilizes constant frequency architecture, noise is minimized, eliminating potential interference with any onboard RF or audio circuitry. Additional features include internal soft-start/inrush current limiting and open LED protection.

The LT3486EDHC is available in a 5-by-3mm DFN-16 package, while the LT3486EFE is housed in a TSSOP-16E package. Pricing starts at $2.50 and $2.60 for 1,000-piece quantities, respectively. Both parts are available from stock.

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