austriamicrosystems unveils smart 1A charge pump for flash LEDs

Dec. 1, 2004
Date Announced: 01 Dec 2004 austriamicrosystems AG, a leading global designer and manufacturer of analog integrated circuits (ICs), has unveiled the world's first smart 1A charge pump for flash LEDs in camera phones. Extending the company's lighting IC portfolio, the two high-current charge pumps, the AS3682 and the AS3683, drive flash LEDs with up to 480mA and 1A output current, respectively.The ICs achieve a peak efficiency of 95% (PLED/Pin) due to supporting automatic mode switching between 1x / 1.5x and 2x modes and through their ultra-low dropout current sinks. The six current sinks can be used with individual LEDs connected in parallel or tied together for driving a single high-output LED. "These smart charge pumps offer significant advantages to designers over inductive boosters in terms of BOM, space and EMI," said Ronald Tingl, Marketing Manager for Power Management in austriamicrosystems' Communications business unit. "Their flexibility, efficiency and small size make them ideally suited for flash, video and lamp applications in camera phones and other handheld devices." The output currents can be adjusted between 15mA and 1A by either a serial interface using soft flash mode or a simple parallel interface using hard flash mode. The hard flash mode is implemented as a 3 pin enable/disable function so that eight different currents can be set for both preview and flash by using only two control wires. This hard flash control method significantly reduces the software effort to embed the IC into a handheld device. The preview and flash start times and duration are controlled individually by either the interfaces or via dedicated preview and strobe inputs. The strobe duration can be set in 100 ms steps up to a maximum of 800ms. Utilizing the dedicated preview and strobe pins enables virtually indefinite lighting duration for easy realization of movie light and lamp functions. Three out of six LEDs can be addressed independently so that additional functions like a movie indicator lamp, a RGB Fun LED or backlighting can be realized with a minimum of additional components.The charge pump runs at a fixed frequency of 1 MHz requiring only two transfer capacitors.In addition, the AS3682 features two programmable General Purpose I/Os (GPIOs), a soft-start function to limit inrush currents, overvoltage protection, thermal shutdown and zero LED current during shutdown. The AS3682 is available in a space-saving 4x4mm QFN24 package. Evaluation kits are available upon request.



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