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Optoelectronics/Displays??

LED driver allows independent control of 18 LEDs

Posted: 17 Jan 2008 ?? ?Print Version ?Bookmark and Share

Keywords:LED driver? programmable displays? lighting devices?

Linear Technology Corp. has announced the LTC3220/-1, an inductorless, low-noise, high-efficiency LED driver for cellphone displays and other programmable lighting applications.

The IC provides 18 individually configurable LED current sources for complete flexibility in programming multiple displays. The display currents are set via a precision internal current reference. The universal current sources can be digitally controlled with independent dimming, brightness, blinking and gradation control, programmable via a two-wire I?C serial interface; the LTC3220 and LTC3220-1 each offer a unique I?C address.

The LTC3220/-1's 2.9-5.5V input voltage range has been optimized for single-cell Li-ion/Polymer battery applications. Efficiencies when driven from a Lithium battery (3.6V nominal) reach 91 percent, with quiescent current as low as 500?A, maximizing battery run-time. Furthermore, slew-rate limited switching reduces conducted and radiated noise (EMI).

The LTC3220/-1's multimode charge pump features low-noise constant-frequency operation, automatically optimizing efficiency based on the voltages across the LED current sources. The device powers up in 1x mode and automatically switches to boost mode (1.5x) when any enabled LED current source approaches dropout; a subsequent dropout switches the device into doubler (2x) mode. Internal circuitry prevents inrush current and excessive input noise during start-up and mode switching. In addition, the device has short circuit and thermal protection.

The LTC3220/-1 is available from stock in the ultrathin (0.55mm) 28-lead QFN (4mm x 4mm) package. The IC requires only five small capacitors for a tiny, complete LED power supply and current controller solution. Pricing starts at $2.35 each for 1,000-piece quantities.




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