Compact VCSEL proximity sensor lends an ear to miniaturisation

Rohm has developed a compact 2.0 x 1.0mm proximity sensor, the RPR-0720. It is optimised, said the company, for applications requiring attachment/detachment and proximity detection, for example in wireless ear buds and wearable devices.
Sensor devices are evolving, driven by miniaturisation and a requirement for functionality. Rohm’s portfolio of proximity sensors combine light emitting and receiving elements in a single package. They are used in a range of applications, from mobile devices to industrial equipment. In wearable device design in particular, there is growing demand for small proximity sensors that can support improved designs and an increase in the number of parts resulting from higher functionality. Rohm said the RPR-0720 is an optical sensor module developed for this sector. The compact proximity sensor integrates a VCSEL and sensor IC.

The RPR-0720 optical sensor module adopts a VCSEL featuring higher directivity than LEDs as the light emitting element and a sensor IC for the light receiving element. The compact size is achieved by optimising the module structure using in-house chips. The result is an area reduced by approximately 78 per cent compared to conventional products, said Rohm.

At the same time, the built-in VCSEL’s wide input voltage range of 2.7 to 4.5V eliminates the need for a peripheral voltage booster circuit (i.e. consisting of a power supply IC, three capacitors, and one inductor) when using a Li-ion battery. This contributes to saving space and increased battery capacity. These characteristics makes it suitable not only for sensing attachment/detachment, but also for detecting various conditions.
The RPR-0720 proximity sensor is suitable for applications that use light reflection to detect conditions as well as attachment/detachment detection of wireless ear buds, smart watches, gaming console controllers and virtual reality (VR) headsets. It can also be used for paper detection in printers, copiers, shredders, and other office automation devices, e-cigarette cartridge/liquid detection and to detect various conditions in smartphones and laptops.

Rohm also offers an evaluation board for the compact RPR-0720 proximity sensor (RPR-0720-EVK).

The RPR-0720 is available from online distributors, Digikey, Mouser and Farnell.

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