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600mA charge pump with dual low dropout linear regulators from AnalogicTech

7th December 2006

Advanced Analogic Technologies Inc., Europe

ES Admin

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By combining a high current charge pump, backlight/keypad drivers, a high output flash driver, and two general purpose LDOs in a single 4x4mm package, and by retaining independent control of the backlight/keypad and flash functions, AnalogicTech’s AAT2842 offers portable system product developers an attractive way to lower parts count, lower the system BOM cost, and build more compact systems without compromising their design flexibility or circuit performance.

AnalogicTech’s AAT2842 is a 600mA charge pump with dual low dropout linear regulators (LDOs) for portable systems operating from Lithium-ion/polymer batteries. Configured as a Total Display Solution, the device features two separate S2Cwire (Simple Serial Control) serial digital interfaces, allowing designers to independently drive up to four LEDs for either display backlight or keypad applications and four LEDs for high-current flash applications.

Previously, many mobile and personal electronics applications powered by a single-cell Li-ion battery, such as smart phones, digital still cameras, and camera-enabled mobile devices, have used separate ICs for backlight and flash functions.

The AAT2842 features a high current tri-mode charge pump capable of driving up to four backlight LEDs up to 30mA each. Alternately, the backlight current outputs can be programmed to drive lower current LEDs for applications such as keypad backlighting. The charge pump can also drive up to four LEDs for flash functions at up to a total of 600mA.

Two separate S2Cwire serial digital interfaces allow designers to independently enable, disable, or set current at up to 16 levels for the backlight/keypad and flash functions. The backlight / keypad and flash LEDs can also be separately controlled via external resistors. To protect the flash LEDs against thermal damage, the AAT2842 also features an integrated flash timer that can be set by an external capacitor.

Integrated into the AAT2842 are two high performance LDOs. Each LDO can supply a continuous load current up to 200mA at a 200mV dropout voltage. Running from the same 2.7V to 5.5V input voltage as the charge pump, the two LDOs are controlled by a single enable input. The output voltage of each LDO is user-programmable from 1.2V to 5V via an external resistor divider. Optimised for battery-powered applications, the LDOs consume only 85µA quiescent current.

The AAT2842 is available in a Pb-free, 4x4-mm, 28-pin TQFN44 package and is specified over the -40 to +85 degrees C temperature range.