Color Controller with Integrated RGB Photosensor for LCD Backlighting

The device has a small footprint and low profile that allows it to easily fit into portable LCD devices where board space is limited. The 5 mm by 5 mm by 0.75 mm integrated color management (ICM) device operates at voltages as low as 2.5 V.

"Avago is the only company that provides a complete off-the-shelf color management solution for LCD backlighting, combining RGB sensors, color controllers and high-brightness LEDs," said Lee Soo Ghee, vice president and general manager for Avago Technologies' Optoelectronic Products Division. "By integrating the sensor and controller into one package, we are expanding the benefits of color management to the growing array of applications using color LCD screens in smaller consumer electronics."

In LCD TVs, the use of LED backlighting with Avago's award-winning illumination and color management (ICM) control has been proven to offer 25 percent richer colors than conventional cold cathode fluorescent lamp (CCFL) backlighting. In addition, LED backlighting totally eliminates the traces of mercury found in CCFLs to meet European Union reduction of hazardous substances (RoHS) mandates.

The ADJD-J823 is a CMOS mixed-signal IC with integrated RGB photosensors designed to be the closed loop optical feedback device of an RGB LED-based backlighting system. This device also has a wide gain control and uses an algorithm to automatically select the optimum gain. A typical system consists of an array of red, green and blue (RGB) LEDs, LED drivers and the ADJD-J823. The device samples the light output from the RGB LED array, processes the color information and adjusts the light output from the RGB LEDs until the target color is achieved.

To do this, the device integrates an RGB photosensor array, an analog-to-digital converter front-end, a color data processing logic core and a high-resolution 12-bit pulse-width modulation (PWM) output generator. By employing a feedback system and the ADJD-J823, the light output produced by the LED array maintains its color over time and temperature.