2A flash driver IC capable of delivering high-intensity WLED lighting for camera phones from AnalogicTech

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 1A current. The two LED current sources share the output current equally. They can be connected together to apply full 2A 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 1A 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 800mA for the AAT1282, but other values can be requested. The step-up converter also helps minimise end product footprint by operating at a high 2MHz switching frequency that allows the use of a compact 1microHenry inductor and 2.2microfarad output capacitor.

“The AAT1282 is a supercapacitor-optimised LED flash driver that allows device designers to harness supercapacitor power-boosts into high-resolution WLED flash units that far outshine standard battery-powered ones and rival Xenon flash units,” said Pierre Mars, vice president of applications engineering for thin-form-supercapacitor-pioneer CAP-XX. “The AAT1282 driver integrates all of the circuitry required to charge the supercapacitor, manage inrush current, and control LED current, thus saving development time, board space, and component cost.”

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 that 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 less than 1.0microA shutdown current, this feature essentially eliminates leakage current.

To protect the device in the event of an output short-circuit condition, the driver IC also features an integrated thermal management system. Built-in circuitry prevents excessive inrush current during start-up.

The AAT1282 is qualified across the -40 to +85 degrees C temperature range. It is available in a 14-pin 3 x 3mm TDFN package.