Digital IR proximity sensing module shrinks always-available earbuds

Believed to be the smallest digital proximity sensor module, the TMD2635 from ams occupies 1.0mm3 for a form factor that enables manufacturers of true wireless stereo (TWS) earbud products to develop smaller, lighter industrial designs. The IR proximity sensor enables wireless earbud in-and-out of ear detection to help extend battery life between charges and can be used in tandem with another TMD2635 to enable elementary touchless gesture control without the need for buttons.

The TMD2635 module integrates a low power infra red vertical cavity surface emitting laser (VCSEL) emitter, two sensor pixels for near- and far-field sensing and a digital fast-mode I2C interface in a miniature land grid array (LGA) package.

As well as enabling small earbuds, incorporating TMD2635 modules in TWS earbud designs extends operation times because it 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 . . . is more than six times smaller by volume than the previous two-in-one IR proximity sensor module.” He added that the split near-far field photodiode offset emitter to detector positioning enables designers to optimise the size and shape of the needed sensor apertures in industrial wireless earbuds and other wearable and portable devices; this can be a 1.5mm circular or a 1.0 x 2.0mm oval aperture.

The TMD2635 module has an average active-mode current consumption of 70 microA and 0.7 microA in sleep mode.

According to ams, 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 IR light measurements to accurate proximity detection results. The proximity detection performance is comparable to that of earlier, larger modules used by the leading smartphone manufacturers.

The TMD2635 is available now in production volumes.

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