Charge Pumps offer independent control of LED banks

Sunnyvale, Calif. — April 5, 2004 — Advanced Analogic Technologies, Inc, (AnalogicTech), a developer of innovative power management solutions, announced today two new additions to its growing family of high efficiency, low noise, constant-frequency charge pumps for white LED applications. The two new devices, the AAT3131 and the AAT3134, offer independent control for two separate banks of LEDs.

The AAT3131 can be used to produce current levels up to 20 mA in three of its outputs and 30mA in a fourth output to drive LEDs from a 2.7V to 5.5V input. The AAT3134 supports six outputs with current outputs up to 20 mA and allows independent control in two groups of four and two. In both devices the outputs can be operated independently or in parallel.

Like AnalogicTech's existing family of charge pumps for white LEDs, the two new parts integrate both a 1.5X fractional charge pump and a 1X load switch to maximize efficiency. The AAT3131 and AAT3134 also feature AnalogicTech's Simple Serial Control (S2CwireTM) interface, a 32-level logarithmic scale LED brightness control that operates through a single wire digital input. This interface provides a significantly simpler design than competitive offerings that require a PWM signal to control LED brightness. The use of constant current outputs ensures uniform brightness control regardless of differences in LED manufacturing lots. They also eliminate the need for current-limiting resistors. AnalogicTech's unique charge pump design also offers significantly lower EMI and noise than an inductor-based boost converter.

Both the AAT3131 and AAT3134 help designers reduce parts count and system footprint in battery-powered portable applications. A high 1 MHz switching frequency enables the use of very small, 1 uF external capacitors (two 1 μF flying capacitors and two 1 μF capacitors at Vin and Vout).

The two new devices also feature thermal management protection, automatic soft-start circuitry and a low current shutdown feature. Both devices are specified to operate across the industrial (-40 to +85 °C) temperature range.

Both devices are available immediately. The AAT3131 comes in a 12-pin TSOPJW package. The AAT3134 comes in a 16-pin QFN package. Pricing for 1000-unit quantities starts at $1.95 and $2.26 each for AAT3131 and AAT3134 respectively.

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