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LED Drivers Combine Backlight, Flash and LDOs On Single Chip

Designed to eliminate multiple ICs in space-constrained portable applications, the AAT2846 and AAT2856 combine backlight drivers, high-current flash drivers and two general-purpose low-dropout (LDOs) linear regulators in a single 4 mm x 4 mm package. The devices also offer independent control for backlight and flash current drive via separate single-wire digital interfaces. 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 the company’s AS2Cwire single-wire interface to independently enable, disable and set drive current for backlight and flash LEDs. Current for backlight LEDs 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 six LED outputs. For maximum white LED brightness uniformity, channel-to-channel backlight current matching is 1%. The devices integrate two low-noise LDOs, each using its own individual enable input and supplying up to 200 mA output current. The output voltage of each LDO is programmable from 1.2V to 5V via a resistor divider. The devices also feature integrated short-circuit and over-temperature protection. Soft start circuitry automatically prevents excessive inrush current at start up and mode transitions. The AAT2846 is qualified across the –40°C to +85°C temperature range and comes in a lead-free, 28-lead, TQFN44 package. It sells for $1.42 each/10,000, while the AAT2856 sells for $1.14 each. ADVANCED ANALOGIC TECHNOLOGIES INC., Sunnyvale, CA. (408) 737-4600


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