SFH 7770 Digital Sensor
Dec 2010OSRAM Opto Semiconductors Inc.Request Info
SUNNYVALE, Calif., Dec. 6, 2010 — The SFH 7770 from Osram Opto Semiconductors combines the functions of a digital ambient light sensor with those of a digital proximity sensor. It determines the ambient brightness, detects the presence of an object nearby and can tell whether the object is moving closer or farther away. Applications in cell phones and smart phones can be controlled without touching the phone. The applications open automatically, and the brightness and volume are adjusted at precisely the right moment.
The digital sensor replaces the usual separate ambient light and proximity sensors and takes up very little space, measuring 2.8 × 2.8 × 0.9 mm. By combining the two functions, it offers added performance and consumes only 350 µA during operation and only 5 µA in standby mode.
The proximity sensor uses the reflection of the emitted light from a separate infrared LED not only to detect objects close to it but also to recognize whether the object is moving toward or away from it. Its high sensitivity in the range from 1 µW/cm² to 10 mW/cm² allows it to operate at long distances of up to 30 cm. With its digital output, the sensor supports the high-speed I²C bus at up to 3.4 MHz.
When it measures brightness, the integrated ambient light sensor immediately returns a lux value of between 3 and 65,000 so that the display brightness can be adapted precisely to the ambient light conditions. This makes the display easier to read and increases the time between battery recharges. The sensor is not influenced by the 50- to 60-Hz fluctuations in the brightness of ambient light produced, for example, by fluorescent lamps.
The digital double pack of proximity and ambient light sensor gives manufacturers of cell phones new freedom of design. Different functionalities can be achieved with just one component. Depending upon the phone, it could be only the proximity function, only the ambient light function, or both. The board design and the number of manufacturing processes are the same in all cases.
Because of the sensor’s high sensitivity, the entire cover can now be made of colored plastic with only minimal loss of range, and there is no need for transparent windows.
By using two further infrared LEDs, it is possible to detect gestures with the SFH 7770. The necessary hardware drivers are already integrated. The IR LEDs transmit light signals at a certain frequency, and the sensor measures the reflections to detect horizontal and vertical movements. Gesture detection from such small components makes contactless control of applications possible even for very small cell phones and smart phones. Users can flick through photos without touching the phone and can disable an integrated touchpad to prevent starting an application unintentionally.