AnalogicTech dual-mode charge pump has simplified control

July 20, 2005
Date Announced: 20 Jul 2005 AnalogicTech has introduced a dual-mode, high efficiency charge pump that supports both white LED backlight and camera flash applications for portable systems that run on lithium-ion/polymer batteries. Today’s handset designers want to retain independent control of LED backlighting and camera flash functions, but each increase in design complexity translates directly into higher cost. By offering independent control through a simple interface with only two input lines, the AAT2806 gives designers the basic functionality they need while minimising the complexity and cost of their design.The AAT2806 uses AnalogicTech’s single-wire Simple Serial Control™ (S2Cwire™) serial digital interface to enable, disable, and set current settings across an 8-level logarithmic scale, offering independent control of LED backlight and camera flash functions.To minimise backlight power consumption during operation, the device adds a light load mode with quiescent current as low as 50µA (typical). The backlight charge pump in the AAT2806 drives up to four LEDs at a total output of 80mA. Current sinks may be operated individually or in parallel to drive higher current LEDs. The charge pump maximises power efficiency by operating in 1X, 1.5X, and 2X modes. The device automatically selects the lowest power mode by comparing the forward voltage of each LED with the input voltage. Low on-resistance of the current sinks minimises the voltage headroom required to drive each LED and helps increase the amount of time the devices stays in 1X mode before transitioning to 1.5X mode. For flash applications, the device integrates a charge pump doubler with a regulated output voltage. It is capable of delivering up to 120mA of continuous current or up to 250mA of pulsed current. An independent enable pin maximizes power savings. The AAT2806’s high 1MHz charge pump switching frequency allows designers to support the device with extremely small ceramic capacitors. By eliminating the use of inductors, the AAT2806 also allows designers to build smaller, lower-profile systems.AnalogicTech’s AAT2806 is available in a Pb-free, thermally-enhanced, 16-pin TDFN44 package and is qualified across the -40 to +85 degree C range.

Phil Dewsbury, Advanced Analogic Technologies, Inc., Europe, 1210 Parkview, Theale, Berkshire, RG7 4TY Tel: +44 (0) 1189 657763 Fax: +44 (0) 1189 657764

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