Flash LED driver from AnalogicTech

3rd October 2007

Advanced Analogic Technologies Inc., Europe

ES Admin

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Datasheet

AnalogicTech has introduced the first in a 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 3x3mm 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. 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-output AAT1270 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 (0.9 mm high) 1µH inductor. Operating off a single-cell Lithium-ion power source, the AAT1270 extends battery life by operating at efficiency levels of up to 85 percent.

The AAT1270 offers designers highly 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 S2Cwire serial interface.

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 AAT1270 also features an asynchronous flash inhibit pin which reduces flash current to movie mode level during periods of high battery demand.

To protect the device, the AAT1270 adds over-voltage, short-circuit and over-temperature protection. Built-in circuitry prevents excessive in-rush current during startup. An automatic shutdown current feature reduces quiescent current to <1.0µA.

The AAT1270 is qualified across the -40 to +85 degrees C temperature range and comes in a Pb-free, 3x3mm, 14-pin STDFN package.

AnalogicTech plans to announce an I2C serial interface programmable AAT1272 in Q407, and an AS2Cwire serial interface programmable AAT1271 in Q108.