Six of them fit on the face of a dime, which is wild.
[1] The world's smallest Bluetooth® Low Energy Module, the new model "HY0021":
A trace at the circumference of the PCB, or a wire antenna that only take up space for the solder joint would do.
The battery/power supply alone is going to be at least an order of magnitude larger in volume.
Indeed, people do use rechargeable lithium batteries like the 50mAh CR322 (22mm by 3mm) or smaller CR311, but these would only be able to handle a 11mA EFR32BG29 output load for a few hours at most... Yet in a mostly dormant power save mode YMMV =3
Microcrystal can make these things to run at <50nA. https://www.microcrystal.com/en/products/real-time-clock-rtc...
All the BLE manufacturers are 1uA plus. It's infuriating.
I'm not familiar enough with the nRF54 series, but it's good to have a few competitors in this space.
> The BG29 chips will be available in 5 mm × 5 mm QFN and 2.6 mm × 2.8 mm WLCSP form factors
That "wireless oral health monitor" example is a concept from Lura Health[1] that integrates a marginally smaller BG27 (2.3mm x 2.6mm WLCSP)[2].
[2] https://www.silabs.com/applications/case-studies/small-bluet...
> and its power consumption is low enough that the device can last from six months to a year on a battery of the equivalent size
The average "width" of the first mandibular molar from this article[1] is 5.1-5.2mm. It sure would be interesting to see a CAD model of the design inside the module on the band. The graphics from the posted article vs. the first link above are also a bit different, making it even harder to infer much I think.