OSRAM's New Ambient Light Sensor for Mobile Phone Applications

OSRAM Opto Semiconductors has announced its newest ambient light sensor (ALS) SFH5711 designed for the mobile device market. OSRAM is the first semiconductor manufacturer to develop a sensor that accurately matches or imitates the sensitivity curve of the human eye. This development enables displays and their related brightness range to be adjusted more precisely than ever before. OSRAM's new ALS SFH5711 will also benefit the automotive market with cockpit dimming and headlight control.

The company's new ALS SFH5711 is an enhanced ChipLED version of its SFH3410 that traditionally has been used in light-dimming applications. However, the newest ALS SFH5711 reaches a new technological benchmark by offering V(lambda) characteristics at a higher level of adaptation. It offers engineers the added benefit of a very small and robust surface-mount technology (SMT) package, which in turn offers the cost savings required for consumer applications, while delivering high optical performance.

The "human eye" properties of OSRAM's ALS SFH5711 were developed through a new material system that replaces traditional silicon. The logarithmic amplifier integrated circuit (IC) further enables a large brightness range (from 3 lx to more than 30.000 lx) to be detected with great accuracy and without the need for various series resistors (to allow sensitivity to be adjusted externally), creating a smaller, more accurate and more cost-effective design. The impressive accuracy of the ALS SFH5711 provides virtually infinite backlight system dimming.

As a result, the spectral sensitivity of OSRAM's new ALS SFH5711 is 560 nanometers (nm), thus mimicking the location where the human eye is most sensitive. The V(lambda) characteristic of the ALS represents the curve on the wavelength spectrum where the human eye sees color. By automatically imitating the characteristics of the human eye, and doing so more quickly than the human eye, OSRAM's ALS SFH5711 is suitable for adjusting the brightness of displays and other such components for optimum readability in constantly changing light conditions. Using a low supply voltage of 2.3 to 5 V, the sensor is energy efficient and ideal for daylight sensor applications where backlight displays must be constantly monitored and/or adjusted. The applications for the ALS SFH5711 include mobile phones, digital cameras, notebook computers, PDAs and handheld global positioning systems (GPS).

The new ALS SFH5711 sensor also prevents the rapid onset of eyestrain often connected to the use of computer laptops and computer monitors' liquid crystal displays (LCDs), a traditional problem if the display is too bright in a dark room. The newest ALS is also a suited solution in automotive applications where it reads ambient light levels and switches headlights on and off.

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