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Flash LED driver suits cellphones with video recording

Posted: 05 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:video recording? flash LED driver? high-end cellphones?

Advanced Analogic Technologies Inc. (AnalogicTech) has announced the first in a new family of flash LED products capable of driving either two LEDs up to 500mA or a single LED up to 1A. Designed to be used with newer-generation, high-current/high-brightness flash LEDs in mobile phones with video recording, the AAT1270 step-up current regulator delivers the high current levels needed to support flash lighting for higher-resolution CCD imagers in a single 3mm x 3mm STDFN package.

"As high-performance mobile phone manufacturers integrate finer-resolution CCD imagers into their devices for improved picture quality, they need flash units capable of generating enough light to make full use of the imager's resolution," says Phil Dewsbury, product line director for AnalogicTech. "Until now they have had to use multiple lower-current, charge-pump-based or more expensive boost converter drivers and multiple lower-current LEDs to meet these high-intensity light requirements. The AAT1270 is capable of delivering the same level of light, as well as support torch or movie-mode capabilities, at lower cost and in a smaller and lower profile package than the more expensive, discrete solutions."

The dual-channel LED driver uses a high-efficiency DC/DC boost converter with small magnetics. It does not require an external Schottky diode. The device's high 2MHz switching speed and low input current ripple permit the use of a low-profile (0.9mm high) 1?H inductor. Operating off a single-cell Li-ion power source, the new device extends battery life by operating at efficiency levels of up to 85 percent.

The AAT1270 promises designers flexible control of flash and movie-mode operation. Full-scale flash LED current is set with a single external resistor. The default current for movie-mode applications is set at a current ratio of 7.3:1. Additionally, the movie-mode current is programmable to 15 other ratios via AnalogicTech's proprietary single-wire S?Cwire serial interface.

Thermal protection
To protect against thermal damage to the flash LEDs, the AAT1270 features a user-programmable safety timer that can be used to terminate a flash event after a prescribed length of time. A separate flash enable pin can be used to initiate both the flash/strobe operation and the safety timer. The device also features an asynchronous flash inhibit pin that reduces flash current to movie mode level during periods of high battery demand.

To protect the device, the AAT1270 adds overvoltage, shortcircuit and overtemperature protection. Built-in circuitry prevents excessive in-rush current during startup. An automatic shutdown current feature reduces quiescent current to <1?A.

The AAT1270 is qualified across the -40C to 85C temperature range and comes in a Pb-free, 3mm x 3mm, 14-pin STDFN package. It sells for $1.42 in 1,000-unit quantities.

AnalogicTech plans to announce an I?C serial interface programmable AAT1272 in Q4 2007 and an AS?Cwire serial interface programmable AAT1271 in Q1 2008.




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