This one is ever so slightly smaller at 3.25 x 8.55 x 0.85mm: https://www.mouser.com/ProductDetail/TAIYO-YUDEN/EYSHSNZWZ?q...

Six of them fit on the face of a dime, which is wild.

Unlike the FDK module, this module requires an external crystal oscillator, which makes me think that the total footprint ends up being larger.

To be fair to Silicon Labs, they don't claim the smallest BLE module but FDK did exactly that [1].

[1] The world's smallest Bluetooth® Low Energy Module, the new model "HY0021":

https://www.fdk.com/whatsnew-e/release20241021-e.html

You wouldn't use a chip antenna if you're that tight on PCB space.

A trace at the circumference of the PCB, or a wire antenna that only take up space for the solder joint would do.

Fractal antenna!

https://en.wikipedia.org/wiki/Fractal_antenna

Limiting factor for what application?

The battery/power supply alone is going to be at least an order of magnitude larger in volume.

"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

if we're talking about a device that only needs centimeters worth of range and spends most of its time in deep sleep, those 50mA could last quite a while.

And would last a whole lot longer if the BLE manufacturers would pull their heads out of their asses and give us a chip with RTC wakeup current that doesn't suck.

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.

The BG22 consumes 0.5 uA in EM4 mode with the BURTC+LFXO enabled.

The Hongjia HJ-131 is much smaller at 4x4x1.3mm https://www.renesas.com/en/document/dst/da14531-honjia-hj-13...

This doesn't have MTP flash or anything though which is a bummer.

This doesn't integrate the antenna, so it's not comparable.

Yes it does. The HJ-131 module has an onboard antenna that’s used by connecting pins 12 and 13.

With the right pcb design you could use this to sneak in an entire microcontroller while making it seem like it's just an antenna, wild