AnalogicTech Introduces New WLED Drivers For Portable Systems Operating Off Single-Cell Li-Ion BatteriesDecember 16, 2007 by Jeff Shepard
Advanced Analogic Technologies Inc. (AnalogicTech) announced the AAT2847, a highly integrated four-channel White LED (WLED) driver for portable systems operating off a single-cell Li-Ion/Polymer battery. The charge pump-based device also integrates two 200mA Low Dropout (LDO) linear regulators, each with its own independent enable pin, to power ancillary system functions.
"The key to success for any portable device is the designer’s ability to configure the end product to meet customer needs in a cost-effective way," noted Phil Dewsbury, Product Line Director for AnalogicTech. "By combining four independently controlled WLED channels adjustable across 52 different current settings, with two independently enabled LDOs, the AAT2847 gives designers maximum flexibility to add new features, such as additional lighting or camera functions, while minimizing cost."
The AAT2847 is built around a low-noise, tri-mode dc-dc charge pump converter which delivers up to 120 mA of output current. Each of the device’s four channels supplies up to 30 mA of bias current for WLEDs. To ensure uniform display brightness, WLED backlight bias current matching is typically 0.5%.
The device uses AnalogicTech’s Advanced Simple Serial Control (AS²Cwire) digital interface to enable, disable and set the current for each backlight LED channel. Current level can be set across 52 levels including sixteen current settings in three separate current scales – 30, 20 and 15mA – as well as four low level current settings which go as low as 50µA.
Each LED channel features embedded short circuit protection and auto disable functionality. A low shutdown current feature disconnects the load from the input and reduces quiescent current to less than 1 µA. The AAT2847 also integrates two LDOs. Each LDO is controlled by its own independent enable input and supplies up to 200 mA output current. Fixed or adjustable output versions are available.
The AAT2847 is qualified across the -40 to +85°C temperature range. It is available in a 20-pin, 3x4x0.75-mm TQFN package. It sells for $1.09 in 1K quantities.