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Charge pump reduces parts count, BOM cost

Posted: 13 Dec 2006 ?? ?Print Version ?Bookmark and Share

Keywords:charge pump? power management? LDO? AnalogicTech? regulator?

AnalogicTech's AAT2842 charge pump

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

The AAT2842 is a 600mA charge pump with dual LDOs for portable systems operating from Li-ion/polymer batteries. Configured as a Total Display Solution, the device features two separate S?Cwire 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.

Tri-mode charge pump
The new device 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 S?Cwire 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 device also features an integrated flash timer that can be set by an external capacitor.

Integrated into the AAT2842 are two high-performance LDOs, each of which can supply a continuous load current up to 200mA at a 200mV dropout voltage. Running from the same 2.7-5.5V 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 1.2-5V via an external resistor divider. Optimized for battery-powered applications, the LDOs consume only 85?A quiescent current.

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




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