Tiny digital IR proximity sensing module enhances earbuds

The IR proximity sensor enables wireless earbud in-and-out of ear detection to help extend battery life between charging and can be used in tandem with another TMD2635 to enable elementary touchless gesture control without the need for buttons.

The TMD2635 module from ams is a complete light-to-digital sensor module which integrates a low power infrared VCSEL (Vertical Cavity Surface Emitting Laser) emitter, two sensor pixels for near- and far-field sensing, and a digital fast-mode I2C interface, all in a miniature land grid array (LGA) package. 

The earbud market is projected to enjoy compound annual growth of 27% in the years to 2023, by which time wireless earbuds are expected to overtake all other wireless and wired product categories to become the most popular type of headphone worldwide.

Consumer audio wireless headset use continues to grow as users further immerse themselves in their modern lifestyles. By incorporating TMD2635 modules in new TWS earbud designs, wearable device manufacturers can appeal to consumers’ desire for smaller, more comfortable wearing products that are available for use for prolonged operational times because it reliably detects when earbuds are inserted or removed from the ear.

Dave Moon, Senior Product Marketing Manager in the Integrated Optical Sensors business line at ams, said: “The TMD2635 underpins ams’ leading proximity sensing position in the consumer electronics market. This latest product occupies 1mm3 of space and is more than six times smaller by volume than the previous two-in-one IR proximity sensor module. 

“And because of the split near-far field photodiode offset emitter to detector positioning, designers of wireless earbuds and other wearable and portable devices have the freedom to optimise both the size and shape of the needed sensor apertures in their industrial designs and optimise their products for comfort and performance, either a 1.5mm circular or a one by two millimetre oval aperture.”

The TMD2635 module power-saving benefits are paramount especially in the small battery capacity and size of a wireless earbud product. It has an average active-mode current consumption of 70µA and 0.7µA in Sleep mode.

The development of the TMD2635 infrared sensor module benefited from ams’ long heritage in optical sensor development and production. ams is the long-time market share leader in proximity, ambient light and colour sensors and sensor modules for mobile phones. ams is a world leader in intellectual property, technologies and production capabilities for miniature optical emitters, photo-detectors and spectral sensors.

The design of the TMD2635’s optical stack and the high performance of the internal laser emitter produce outstanding crosstalk rejection, high immunity to interference from ambient light, and highly effective algorithms which convert infrared light measurements to accurate proximity detection results. The proximity detection performance of the TMD2635 is comparable to that of earlier, larger modules used by the leading smartphone manufacturers, but in a significantly reduced form-factor appropriate for the small design spaces available in wearable devices.

The TMD2635 is available now in production volumes. Unit pricing is $0.89 in an order quantity of 1,000 units.