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Charge pump fields both camera lighting and flash

Posted: 28 Mar 2005 ?? ?Print Version ?Bookmark and Share

Keywords:advanced analogic technologies? charge pump ic? at2801? led?

Advanced Analogic Technologies' first multi-function charge pump IC, the AAT2801, simultaneously supports white LED backlight and camera flash functions for portable systems powered by Li-ion/polymer batteries.

The device, actually two charge pumps in one, uses one charge pump to drive up to four LEDs for backlighting, delivering up to 30mA on each current source output. The second charge pump's circuitry delivers a peak output of 300mA for flash.

"As the first device in AnalogicTech's family of multi-function power management chips, the AAT2801 charge pump allows us to address today's complex portable applications with a single, 4-by-4mm, low-power solution," said Kin Shum, director of Strategic Marketing. "By integrating white LED backlight and camera flash technologies into a single, 16-pin TDFN44 package, this new device allows OEMs to support two important lighting functions while reducing the board space by more than 30 percent."

The backlight charge pump operates in the 1x, 1.5x and 2x modes to maximize efficiency. The company's AutoBias technology allows the device to automatically select the appropriate voltage rail for each LED by comparing the forward voltage with the input voltage. A single-wire Simple Serial Control (S2Cwire) digital interface is used to control LED drive current with a 32-level logarithmic brightness scale.

For flash applications, the AAT2801 integrates a charge pump with a regulated output stage. Delivering up to 120mA of continuous current for "movie-mode" or up to 300mA of pulsed current for camera flash, the circuit adds an independent enable pin to maximize power savings.

A built-in thermal management circuit protects the device from fault conditions. Soft-start circuitry prevents excessive inrush current during start-up. The AAT2801's 1MHz switching frequency allows designers to support the device with extremely small ceramic capacitors.

The AAT2801, rated for operation over -40C to 85C, is available for $1.82 each in 1k quantities.

- Vincent Biancomano


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