In bright sunlight, drivers may not be able to read the satellite navigation screen or can only guess what speed is shown on the speedometer. Osram says that with the help of ambient light sensors, however, the backlighting of such automotive displays can be regulated to enable reading in all weather conditions and sun brightness levels.
The SFH 5701 A01 ambient light sensor is Osram Opto Semiconductors’ first IC-based ambient light sensor (ALS) component for which a separate power supply pin is not required. The ALS is an active component in which the IC gets its power via the signal current and is therefore not reliant on an external power supply. For this reason, the device has only two pins instead of three or more, making it much easier to connect and operate.
The special filter encapsulation of the SFH 5701 A01 allows primarily green light through and filters out infrared wavelengths very efficiently. This green light sensitivity mimics the spectral sensitivity of the human eye, which also is most sensitive to light in the green range of the visible spectrum. Overall, like the human eye, the sensor detects light in the spectrum between 450 nm and 700 nm, the visible range.
New ALS an Analog Component
SFH 5701 A01 is an analog component with a linear integrated amplifier, which supplies a typical signal of 135 µA at 100 lux. Osram says that the high sensitivity at a low illuminance of just 0.01 lux and high dynamic range combine to produce reliable light measurements for a wide range of ambient light conditions.
Moreover, the ALS provides precise measurements even behind dark glass or plastic covers, an important benefit for passenger cell designs. The compact ALS measures 1.25 mm x 2.0 mm x 0.8 mm. And despite being very sensitive to light level variation, integrated thermal compensation makes the component insensitive to temperature fluctuations.
“The dark green encapsulation of the package of our SFH 5701 A01 offers many benefits, not least in terms of design. The component is unobtrusive in the car, particularly if installed behind a semi-transparent cover. Together with its small size and high sensitivity, this makes the component a particularly versatile and efficient solution for many different in-car applications,” said Walter Rothmund, marketing manager automotive for the emitter laser sensor section at Osram Opto Semiconductors.