High speed PIN photodiode slim down sensor designs for wearables

Broadening its optoelectronics portfolio, Vishay Intertechnology has the VEMD8080, a high speed silicon PIN photo diode with enhanced sensitivity for visible light.

It has a rectangular 4.8 x 2.5mm top-view, surface-mount package with a low profile of just 0.48mm. According to Vishay, this is 0.37mm lower than that of competing solutions. The VEMD8080 also has low capacitance of 47pF for precise signal detection in wearable devices and medical applications.

Its radiant-sensitive area measures 4.5 mm² and the photo diode has high radiant sensitivity with a reverse light current of 28-microA and dark current of 0.2 nanoA. The VEMD8080 uses Vishay’s wafer technology to detect visible and near infra red radiation over a wide spectrum range from 350 to 1100nm. For green LEDs, the VEMD8080’s sensitivity represents a 30 per cent improvement over the standard technology in previous-generation solutions, reports Vishay.

When used with green LEDs, such as Vishay’s VLMTG1400, the photo diode’s small size and high sensitivity enable slim sensor designs for optical heart rate detection in wearable devices such as fitness trackers and smartwatches. In these devices, the VEMD8080’s rectangular shape allows several light emitting diodes to be placed close to the radiant sensitive area to maximise the signal. When combined with 660 and 940nm dual colour emitting diodes, the photo diode is also suitable for SpO2 measurement in medical monitors.

The VEMD8080 features a ±65 degree angle of half-sensitivity, an operating temperature range of -40 to +85 degree C, and 950nm wavelength of peak sensitivity.

The photo diode is RoHS-compliant and halogen-free, and provides a moisture sensitivity level (MSL) of 4 in accordance with J-STD-020 for a floor life of 72 hours.

Samples of the VEMD8080 are available now. Production quantities will be available in March 2018, with lead times of eight to 10 weeks for large orders. A product demo board is available from MikroElektronika and Vishay distributors.


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