Multifunction LED Drivers Simplify Lighting Circuit Design by Combining Backlight, Flash and LDOs into Single Chip

The AAT2846 and AAT2856, combine backlight drivers, high-current flash drivers and two general purpose low-dropout (LDOs) linear regulators in a single 4x4 mm package. Designed to eliminate multiple ICs in space-constrained portable applications, these new devices also maximize design flexibility by offering independent control for backlight and flash current drive via separate single-wire digital interfaces.

“As today’s high performance handsets and other portable devices rapidly evolve and add new features, their lighting functions are growing increasingly complex,” says Adolfo Garcia, product line director for AnalogicTech. “Many now require WLEDs for backlight of large and sophisticated main displays, WLEDs for backlight of smaller sub displays, and flash LEDs for camera functions. By combining six outputs for WLEDs, two for flash and two LDOs on the same chip, and providing independent control for each function, the AAT2846 and AAT2856 Total Display Solutions offer portable system designers the opportunity to build dramatically smaller and more economical portable systems.”

No Performance Compromise:
The AAT2846 uses a high current, tri-mode charge pump capable of driving up to six backlight LEDs at 30 mA each and two flash LEDs at up to a total of 600 mA. For applications that do not require flash functionality, the AAT2856 offers a high current tri-mode charge pump designed to drive six backlight LEDs at up to 30 mA each.

Both devices feature AnalogicTech’s AS2Cwire™ single-wire interface to independently enable, disable and set drive current for backlight and flash LEDs. Current for backlight LEDs on the AAT2846 and AAT2856 can be programmed to any of 32 levels ranging from 95 µA to 30 mA. The devices also provide a 20 mA full-scale range and a special low-current address for optimal performance at low LED current levels. The six backlight outputs can also be segmented into a 5 + 1 configuration to support dual-panel mobile handset applications. In addition, a special operating mode can be invoked to provide individual control of each of the (6) LED outputs. Thus, any custom arrangement for main/sub panel displays, keypad illumination, general-purpose status indication, or flash indication can be programmed. For maximum white LED brightness uniformity, channel-to-channel backlight current matching is 1%.

On the AAT2846, current on the two flash outputs can be programmed to any of 16 settings up to 300 mA for each (600 mA total) via an external resistor. For uniform power dissipation, channel-to-channel flash current matching is 4%.

Both devices integrate two high-performance, low-noise LDOs. Each LDO uses its own individual enable input and supplies up to 200 mA output current. Intended to supply the basic power requirements of functions such as a housekeeping controller or a camera module, the output voltage of each LDO is programmable from 1.2V to 5V via a resistor divider. By offering two separate controls for the LDOs, the AAT2846 and AAT2856 give the system designer added flexibility when sequencing multiple external power supplies.

The AAT2846 and AAT2856 also feature integrated short-circuit and over-temperature protection. Soft start circuitry automatically prevents excessive inrush current at start up and mode transitions.

Price and Availability :
The AAT2846 is qualified across the -40 C to +85 C temperature range and comes in a Pb-free, 28-lead, TQFN44 package. It sells for $1.42 in 10K quantities. The AAT2856 sells for $1.14 in 10K quantities.

About AnalogicTech:
Advanced Analogic Technologies Incorporated (AnalogicTech) is a supplier of power management semiconductors for mobile consumer electronic devices, such as wireless handsets, notebook and tablet computers, smartphones, digital cameras, and digital audio players. The company focuses its design and marketing efforts on the application-specific power management needs of consumer, communications, and computing applications in these rapidly evolving devices. AnalogicTech is headquartered in Sunnyvale, California, with offices in Beijing, Hong Kong, Japan, Shanghai, Shenzhen, South Korea, Sweden, and Taiwan, as well as a worldwide network of sales representatives and distributors. For more information, please visit the AnalogicTech website: www.analogictech.com.