AnalogicTech LED Backlight Drivers with CABC Save Power and Smooth Brightness Transitions in Handheld Devices

“Two of the key issues facing the use of white LEDs in handheld devices center around power consumption and smooth transitions between brightness levels,” said Phil Dewsbury, product line director for display and lighting for AnalogicTech. “With consumers demanding both long battery lifetimes and an enhanced user experience, the feature sets in these new products offer critical market advantages. The CABC feature can reduce power consumption by as much as 50 percent, while offering automated LED fading to improve user satisfaction while simplifying programming by transferring the burden of communicating and timing the fading of the LED current.”

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 AS2CwireTM 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.

“These products further move AnalogicTech towards delivering integrated, feature-rich devices for LED backlight,” continued Dewsbury. “We have rapidly grown our backlight driver family with nearly 50 now available and five using this charge pump architecture. Adding new and unique features to expand our portfolio, while at the same time replacing older products with updated and smaller designs, is key to maintaining our leadership position as the backlight supplier to the mobile phone industry and bringing in new customers in other related portable applications.”

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.