The IR Topled D5140 is a further development of the SFH 2440 photodiode which Osram Opto Semiconductors has recently introduced for fitness sensors. A pre-molded package soldered to the bottom of the package forms the basis of the new component. Previously offered packages had to be soldered to side legs. Because these legs are no longer there in the new design, the Topled D5140 is around 1.4 mm shorter, now measuring 5.1 millimeters (mm).
The electrical and optical properties of the new photodiode are identical to those of its counterpart, the SFH 2440. Along with the short switching time of typically 90 nanoseconds, the spectral sensitivity optimized for visible light is particularly noteworthy, with a maximum sensitivity of 620 nanometers. However, in the infrared spectral range the sensitivity of the two photodiodes is greatly suppressed.
Precise heart rate measurements
Just like the SFH 2440, the IR Topled D5140 is also ideal for optical sensors for pulse rate measurements, on the wrist for instance. It works by shining visible light on the surface of the skin, some of which is absorbed or reflected to the detector. Because arterial blood absorbs more light than the surrounding tissue, the strength of the detector signal changes with the volume of blood through which the light passes. The periodicity of the signal indicates the heart rate. However, infrared light which shines onto the measuring point from the surroundings and disperses in the body also reaches the photodiode.
The Topled D5140 offers an outstanding signal-to-noise-ratio because it registers the reflected light particularly well while at the same time suppressing the infrared light. Thanks to its short switching time, the light signal modulated with the heart rate can be time-resolved perfectly. “The IR Topled D5140 allows our customers to design more compact sensors, preserving the high signal quality offered by the SFH 2440 so far”, said Dr. Chris Goeltner, Project Manager Infrared at Osram Opto Semiconductors.
• IR Topled D5140
• Dimensions 5.1 mm x 4.0 mm x 0.85 mm
• Photosensitive area 7.02 mm2
• Wavelength of maximum photosensitivity 620 nm
• Rise and fall time 90 ns
• Maximum operating temperature 100° C
Applications which so far have been using large-area photodiodes such as the SFH 2440 or SFH 2430 as ambient light sensors can also be made smaller with the new component. In the near future, Osram wants to offer a photodiode with broadband spectral sensitivity in the new package for its automotive customers too.
Thanks to a new package, Osram Opto Semiconductors reduces the length of its large-area photodiodes by about 20 percent. The first product from this series is the IR Topled D5140 which has been optimized for the detection of visible light.
OSRAM with headquarters in Munich, Germany is a globally leading lighting manufacturer with a company history of around 100 years. The product spectrum contains high-tech applications based on semiconductor technologies such as infrared and laser. Products are used in a wide variety of applications ranging from virtual reality, autonomous driving and mobile phones to networked, intelligent lighting solutions in buildings and cities. The company is global technology and market leader in the automotive lighting technology sector. OSRAM had approximately 24,600 employees around the world in continued business sectors (without Ledvance) with turnover of 3.8 billion euros to the end of the 2016 fiscal year (30 September). The company is listed on the Frankfurt am Main and Munich stock exchanges under WKN: LED 400 (stock exchange symbol: OSR). For further information, see www.osram.com.