LED driver delivers high-intensity lighting for camera phones

Santa Clara, Calif. — Advanced Analogic Technologies Inc. (AnalogicTech) has claimed the industry's first 2-A flash LED driver IC capable of delivering high-intensity light from white LEDs (WLEDs), targeted at camera phones. Combining a high-frequency boost converter with fixed input current limiting, dual-output regulated current sinks and I2C control, the AAT1282 uses a supercapacitor to deliver the high peak current needed to support the high-intensity flash required for mobile phones featuring cameras with resolutions of 5 megapixel and higher while protecting the battery.

Operating across a 2.7 to 5.5-V input, the AAT1282 is designed for LED photo flash applications in a variety of single-cell Li-ion powered products. The high-efficiency, high-current step-up converter features two output current sinks, each providing a regulated 1-A current. The two LED current sources share the output current equally. They can be connected together to apply full 2-A output current into a single white LED or each diode can be connected to its corresponding current source and the driver can provide two independently-controlled 1-A outputs.

Designed specifically to charge a supercapacitor, the step-up converter features an integrated fixed input current limiter to limit the battery current and to avoid large voltage drops that can cause the phone to reset. Current limit is set at 800 mA, but other values can be requested. The step-up converter also helps minimize end product footprint by operating at a 2-MHz switching frequency, which allows the use of a compact 1uH inductor and 2.2u F output capacitor.

The WLED driver uses an industry-standard I2C serial digital input to enable, disable and set the movie-mode (torch) current for each flash LED across 16 levels. The I2C interface is also used to set flash/movie-mode current ratio, output channel control and safety timer. Maximum flash and movie-mode current is set by a single external resistor. The ratio between flash and movie-mode current is preset at 7.3:1 but can be adjusted to a wide range of other values.

An independent flash enable is provided to initiate the flash operation and to control a default timer, which can be used to terminate a flash event at the end of a user-programmed delay or as a safety feature to prevent the LED from over-dissipating in the event of a software failure.

The AAT1282 also features a true load disconnect function that isolates the load from the power source while in the OFF or disabled state. By guaranteeing <1.0 uA shutdown current, this feature essentially eliminates leakage current, AnalogicTech said.

To protect the device in the event of an output short-circuit condition, the AAT1282 also features an integrated thermal management system. Built-in circuitry prevents excessive inrush current during start-up. The LED driver is qualified across the -40°C to +85°C temperature range. It is available in a 14-pin, 3 x 3-mm TDFN package.

Pricing: $1.75 in quantities of 1,000.

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