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LED flash drivers offer design optimization

Posted: 11 May 2009 ?? ?Print Version ?Bookmark and Share

Keywords:supercapacitor? flash driver? LED?

Supercapacitor-optimized LED flash driver

CAP-XX Ltd, developer of the supercapacitor-driven BriteFlash Power Architecture, is introducing supercapacitor-optimized LED flash drivers from several power management IC (PMIC) companies to optimize the design of high-power LED flash units for high-resolution camera phones and digital cameras.

AnalogicTech's AAT1282 and ON Semiconductor's CAT3224, and soon-to-be-released NCP5680 supercapacitor-optimized LED flash drivers team with a thin, prismatic supercapacitor to drive high-current white LEDs (WLEDs) in a thin-form solution that provides comparable light energy to a bulky xenon flash. These LED flash drivers integrate all circuitry required to charge the supercapacitor, manage in-rush current and control LED current, thus saving development time, board space and component cost. Both Seoul Semiconductor and ON Semiconductor have created LED flash module reference designs that demonstrate the thin-form BriteFlash solution.

"This is valuable for our customers, since it offers a more integrated approach to incorporating BriteFlash into small mobile handsets and digital cameras," said Peter Buckle, CAP-XX VP of sales and marketing. CAP-XX also claims that more supercapacitor-optimized LED flash drivers are in late-stage development at other PMIC companies.

To produce high-resolution pictures in low-light conditions, cameras of 5Mpixels or more require a high-intensity flash. Today's WLEDs can deliver such light energy, but need up to 400 percent more power than a battery can provide. To support the battery, a thin supercapacitor can drive the LED flash to full intensity while also handling other peak-power needszoom, auto-focus, audio, video, wireless transmissions, GPS readings and RF amplificationwithout compromising slimline design.

CAP-XX developed the BriteFlash Power Architecture to give designers a thin-form LED flash solution that delivers light energy that far exceeds standard battery-powered LED flash and rivals xenon flash.

BriteFlash combines an LED flash driver IC, supercapacitor, battery and WLEDs. The flash driver's boost converter charges the supercapacitor to 5.5V, which then delivers high-peak current to drive the LED flash. The battery only supplies average power and recharges the supercapacitor between flashes.

Supercapacitor-optimized LED flash drivers integrate tools to manage the supercapacitor in power-hungry portable applications. ON Semiconductor's low-power business unit director, Marie-Therese Capron, explained their two solutions. "While CAT3224 is an integrated 4A LED driver for compact camera-flash design, our upcoming NCP5680 is a 10A LED driver featuring fully-programmable outputs via I?C interface, and power regulation capability to drive other power-hungry circuitry such as audio. Both solutions provide high-intensity photo flash plus continuous lighting for capturing video in dark environments."

Phil Dewsbury, product line director for AnalogicTech said, "Li-ion batteries simply cannot supply the high-peak currents required for high-intensity LED flash. Supercapacitors can store the required energy while keeping the form factor small. However, charging them quickly while minimizing battery current presented a unique challenge. Our solution was the AAT1282, a 2A, dual-output LED flash driver IC."

- Paul Buckley
Power Management DesignLine Europe

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