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LED/CAM driver targets cell phone displays/lighting

Posted: 19 Apr 2007     Print Version  Bookmark and Share

Keywords:CAM driver  LED camera light  cell phone display 

Linear Technology Corp. has announced the LTC3207, an inductorless, low-noise, high-efficiency LED/CAM driver for cell phone displays and lighting. The IC provides 12 individually configurable current sources for main, sub, RGB, auxiliary or general-purpose (GPO) displays/lights/outputs, plus drive capability for one high-current 400mA LED camera light. The universal current sources have digital control with independent dimming, brightness, blinking and gradation control, programmable via a simple two-wire I²C serial interface.

Camera flash (pulsed) or torch (continuous) current levels can be selected real-time by the CAMHL pin, or alternatively, controlled by the I²C port. The LTC3207's input-voltage range of 2.9-5.5V has been optimised for single cell Li-ion/polymer battery applications. When driven from a lithium battery (3.6V nominal), efficiencies reach 92 per cent, with a quiescent current of only 500µA, maximising battery run-time. Slew-rate limited switching reduces conducted and radiated noise (EMI).

The LTC3207's multi-mode charge pump features low-noise constant-frequency operation, automatically optimising efficiency based on VIN and LED forward voltage conditions. 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 shortcircuit and thermal protection.

The LTC3207 is available from stock in the low-profile 24-lead QFN (4-by-4mm) package. The IC requires only five small capacitors to create a tiny, complete LED power supply and current controller solution. Pricing starts at Rs.88 ($1.95) each for 1,000-piece quantities.

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