AnalogicTech 2A Flash Driver IC Delivers High Intensity WLED Lighting For Camera Phones
Advanced Analogic Technologies Inc. (AnalogicTech) announced the AAT1282, which it describes as the industry’s first 2A flash LED driver IC capable of delivering high intensity light from White LEDs (WLEDs). Combining a high frequency boost converter with fixed input current limiting, dual output regulated current sinks and I²C control, the new device 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.
"Several LED vendors have announced products which approach the light intensity of a conventional Xenon flash, the de facto yet bulky standard in today’s high-resolution digital still cameras or smartphones," stated Phil Dewsbury, Product Line Director for AnalogicTech. "But the adoption of LED flash in portable applications has until now been limited due to the high levels of battery current, forward voltage, and peak current required to produce this intensity. By storing the output of a boost convertor in a high-capacity supercapacitor, the AAT1282 allows designers to use WLEDs to deliver the high-intensity light needed for flash and video applications in high megapixel cameras without draining or damaging the battery."
Operating across a 2.7 to 5.5V 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 minimize end product footprint by operating at a high 2 MHz switching frequency which allows the use of a compact 1uH inductor and 2.2µF 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. To protect the device in the event of an output short-circuit condition, the new 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°C temperature range. It is available in a 14-pin 3 x 3mm TDFN package. The device sells for $1.75 in 1K quantities.
