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ST announces ambient light, colour sensing solutions

Posted: 08 Feb 2007     Print Version  Bookmark and Share

Keywords:STMicroelectronics  colour-sensing IC  optical feedback  sensing applications  VM6101 

STMicroelectronics has announced its first highly-integrated light and colour-sensing IC intended for a wide range of optical feedback and sensing applications, including mobile phones, notebook PCs and LCD TVs. The VM6101 is the first product in the market to offer both colour and ambient light sensing, with an embedded system interface that needs no external components–a cost-saving feature for manufacturers. The VM6101 is sutiable for automatic LCD backlight control CCFL or white LED.

The battery life of portable display products such as DVD players, camcorders, and digital cameras, as well as mobile phones and laptop PCs, is highly dependent on the power used by the LCD and on its brightness setting. These sensors, with a standard System Management Bus interface, are easily integrated into any system to enable the LCD to be adjusted automatically to match ambient lighting conditions. In addition, the VM6101 can be used to provide colour balancing adjustment for projection systems and RGB backlighting.

The light sensor is the first in a series of imaging products. It has been developed using the technical expertise of ST's Imaging Division in the fields of CMOS imager-on-chip devices and colour processing for camera applications, in which ST is a market leader*, to satisfy the need for an integrated, low-cost light sensor for a variety of automatic backlight control applications. In contrast to most imaging markets, where the general trend is towards more pixels for higher resolution, the VM6101 has four (red, green and blue, and one with no filter), to measure total ambient light level and the separate RGB colour components.

Various discrete solutions based on monochrome light-to-voltage sensors have been available in the market, but most require additional processing or conversion circuitry to operate as part of a complete application, thus resulting in a significantly higher bill of materials; the few solutions that can perform colour light measurement carry a heavy premium, which precludes many high-volume consumer applications. In contrast, the VM6101 measures Yellow, Red, Green, and Blue components separately on a single chip, which also includes all system components and uses an industry-standard communication bus for data readout and device setup – all at an attractively low price.

Part-to-part matching methods in manufacture ensure repeatable light measurements, while pixel-to-pixel matching in the VM6101 is better than ±one per cent (over the full illumination range, at constant temperature). The sensor's spectral response is matched to that of the human eye through novel frequency-response shaping techniques that reject the IR spectrum, and a very wide dynamic range from 30mLux to 30KLux is achieved by using a light-to-frequency pixel architecture. The device features very low power consumption of 1mA in active mode, and just 1µA in standby mode.

In addition to features that reduce system cost and complexity when used with MCU-based controllers, the VM6101 also offers autonomous operating modes to further reduce or eliminate the CPU overhead. A PWM output can be programmed to give direct control of an LED driver IC, using the data from any of the four sensor pixels. Also, a highly flexible automatic light threshold detector can generate an interrupt signal to alert the system to a change in ambient light.

The VM6101 is based on ST's proprietary CMOS sensor technology and will be manufactured at the company's leading-edge facilities at Crolles, France. The device is packaged in a tiny 3-by-3-by-0.7mm 8-lead optical MLPD package. Pricing for the VM6101 is Rs.34.90 (77 cents) for quantities of 10,000 units per year.




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