Power Electronics

Drivers Offer Adaptive Brightness Control and Auto-Dimming

Advanced Analogic Technologies, Inc. introduced the AAT2868 and AAT2869 LED backlight drivers. The AAT2868 and AAT2869 are 1x/1.5x dual-mode, high-efficiency charge pump based white LED backlight drivers that drive four constant current LED channels and now offer content adaptive brightness control (CABC) or dynamic backlight control (DBC) to further reduce power consumption by up to 50 percent. To form a complete lighting solution, both devices include two linear low drop-out (LDO) voltage regulators.

For CABC and dimming functions, the AAT2868 provides the user with a pulse-width modulation (PWM) dimming input for external brightness and fading control that functions in parallel to the fully scaled 32 step LED current that is programmed though the AS2C wire™ interface. The AAT2869 replaces the manual PWM input with an AS2C based auto-dimming and fade capability that reduces requirements on system resources. The AAT2869 automated fade-in and fade-out feature makes backlight turn-on and turn-off more visually pleasing. Both backlight drivers deliver improved power savings by allowing the system to continuously adjust the backlight current level in relation to the displayed image.

The AAT2868 and AAT2869 are high-efficiency, low-noise, constant-frequency, dual-mode (1x/1.5x) charge pump DC/DC converters capable of driving four white LEDs at a total 124mA from a 2.7V to 5.5V input. The integrated dual linear LDO regulators are independently programmable from 1.2V to 3.0V at a total load of 150mA each. These LDO voltage regulators can be used to power an additional display controller, CMOS image sensor, vibration motor or other accessories.

The AAT2868 and AAT2869 offer significant flexibility for implementation, with the easy-to-use single wire AS2Cwire interface to enable LED dimming options in 32 current steps, smooth fading transitions and LDO programming. Both are provided in a compact, low-profile TQFN package that has a 76 percent smaller footprint compared to discrete solutions. These new drivers are ideal for power-sensitive battery operated handheld applications with LCD displays of up to 3.5 inches. Such devices include smart phones, personal navigation devices, portable media players, portable medical equipment and portable industrial instrumentation.

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