High Efficiency Charge Pumps – for driving white LEDs

Advanced Analogic Technologies Inc (AnalogicTech), announced a generation of high efficiency charge pumps for white LED applications. Designed to maximize power efficiency in battery-powered portable designs, the AAT3140 and AAT3141 charge pumps combine a loadswitch (1X) with fractional (1.5X) and doubling (2X) conversion to support LEDs with a wide range of forward voltages (VF). The AAT3140 produces current levels up to 30 mA on each of four current source outputs. The outputs may be operated individually or in parallel. The device can be used to drive a wide variety of LED configurations from a 2.7V to 5.5V output. Unlike boost converter-based solutions which demand physically large, external inductors, these low-noise, constant frequency charge pumps operate at a high 1 MHz switching frequency and require only four small (1F) external capacitors. The design also offers lower EMI and noise than an inductor-based boost converter. The AAT3140 also provides 32-position logarithmic scale LED brightness control. The AAT3141 offers all the same features as the AAT3140, but adds addressability to its digital input control. This Advanced Simple Serial Control (AS2Cwire) interface allows designers of portable devices that run multiple displays, such as clamshell-style cell phones, to independently control three LEDs to backlight a main display and one LED (or two in parallel) to backlight a sub-display. Advanced Analogic Technologies, Theale, Berkshire RG7 4TY, UK.

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