SFH 7773 Digital Sensor
Sep 2011OSRAM Opto Semiconductors Inc.Request Info
SUNNYVALE, Calif., Sept. 9, 2011 — The “three in one” SFH 7773 digital sensor from Osram Opto Semiconductors combines an infrared LED emitter with proximity and ambient light sensors in one compact unit. Combined emitter and detector chips streamline smartphone design and eliminate crosstalk.
The sensor facilitates installation of proximity and ambient light sensing in smartphones and similar devices by combining the functions of a digital ambient light sensor and a digital proximity sensor. It simplifies the elimination of crosstalk by combining the emitter and detector chips together – three devices in all – circumventing the design requirements that are usually necessary to suppress crosstalk. Designers no longer have to install a separate IR emitter to enable the proximity sensor function.
The SFH 7773 detects objects up to a distance of 15 cm while simultaneously measuring the intensity of the ambient light. Its black package, measuring 5.3 × 2.5 × 1.2 mm, is barely noticeable behind the transparent covers of smartphones. Power consumption is 5 μA maximum in standby mode, 300 μA in operational mode, making it suited for portable devices.
Proximity sensors detect objects by receiving the reflection of an emitted light signal. But the cover of a smartphone also reflects light back to the sensor. This crosstalk is usually intercepted by installing an optical barrier or placing the emitter at a sufficient distance from the cover to prevent the cover reflections from reaching the detector. However, both methods are complex and cumbersome. Inside the SFH 7773, the device, the emitter and the detector chip are located sufficiently far apart and apertures are integrated into the package to prevent or significantly reduce crosstalk.
Designers can select the integration time of the detector and, thus, the detection range of the proximity sensor via the I2C interface. They can also adjust the ambient light sensor to the transparency of the smartphone cover. A variety of sensitivity levels is available, ranging from 3 to approximately 65,500 lx.