A color sensor with five integrated channels accurately measures the Correlated Color Temperature (CCT) of lighting. As the use of sensors continues to expand in today's mobile electronics market, manufacturers of mobile devices such as smartphones, tablets, and laptops can provide users with an excellent visual experience by using measurement techniques that can dynamically adjust the display color palette.

In addition to the addition of traditional Red, Green, and Blue (RGB) color sensor channels, a dedicated IR measurement channel is included to reliably detect infrared (IR) signals from ambient light sources. This allows standard cameras and smartphones to adjust the color temperature of the flash and take better photos in indoor and outdoor environments. Color measurement is affected by changes in the IR content of light. Therefore, a passband clear (C) channel photodiode is included to provide a direct measurement reference that mathematically adds or subtracts unwanted residual IR energy. The integrated IR blocking filter in the RGBC photodiode minimizes IR spectral component effects and supports improved color accuracy measurements.

The fifth IR channel is sensitive to IR light in the spectrum of 700nm–1,100nm. Since every light source has its own spectral fingerprint based on the known ratios of ultraviolet (UV), RGB, and IR light sources, the system can identify light sources around the user by measuring the ratio of IR to C or red to C channels and applying a detection algorithm to the measurements. In smartphone camera applications and digital still cameras, the ability to reliably detect light sources enables the optimization of white balance settings in the camera or smartphone flash, thereby further improving image quality.

By measuring the CCT and brightness (lux) of ambient lighting in the system, consumer electronic devices can automatically adjust the display's color tone for the best visual experience, even when light attenuation and spectral distortion occur due to various lighting conditions, dark inked glass, and materials. By adjusting the display's color tone and hue, the device can make images appear more vivid, natural, and smooth under any changing lighting conditions.

Four independent Analog-to-Digital Converters (ADCs) are used one for each RGB channel, and a fourth ADC is shared between the Clear and IR channels, allowing all four channels to be sampled simultaneously. Therefore, CCT and lux measurement errors are eliminated under rapidly changing lighting conditions. The TCS3490's sensor photodiode features a radial structure, producing a uniform and optimized response regardless of the angle of the incident light. It provides a uniform and optimized response, particularly when positioned under a circular window hole structure. Through a level-shifter style interrupt pin, the sensor can alert the application processor when preset light and color measurement thresholds are crossed, eliminating the need for continuous I2C bus polling. Consequently, it reduces overall system power consumption and extends battery life.

“The consumer electronics touchscreen display market is highly competitive, and manufacturers can gain a competitive edge by differentiating their brands through more intelligent display management capabilities. With the TCS3490’s five-channel color sensor, manufacturers can not only make display colors appear sharper and more attractive but also adapt them to the user’s eye in both indoor and outdoor lighting conditions. This is because the product’s CCT measurements closely match what the human eye perceives as color and brightness,” said Davdi Moon, Senior Product Marketing Manager and head of ams’ advanced optical sensor business unit.

Price and Purchase Information:

The TCS3490 color sensor is available in a 2.0mm x 2.4mm DFNL package and is currently available in bulk. The price is $1.40 per unit for quantities of 1,000. A demo board for the TCS3490 is available online at ams. For more information on the TCS3490 and to request samples, please visit www.ams.com/Color-Sensor/TCS3490.