STM32WL UFBGA73 – direct-tie (no RF switch) possible with RFO_LP only?

[Jash]

Hi all,

I'm designing a LoRa node with STM32WL55JCU6 (UFBGA73), using RFO_LP only (+14 dBm, high band 868 MHz). My starting point is the MB1842 reference design, which uses a BGS12SN6 RF switch between the TX and RX paths.

For UFQFPN48, ST provides direct-tie reference designs without a switch (MB1789). For UFBGA73, both MB1842 and MB1849 use an RF switch, and I couldn't find a direct-tie BGA73 reference.

Questions:
1. Is direct-tie recommended on UFBGA73 in LP mode?
2. Has anyone implemented it on BGA73? If so, what matching network did you use, and how did TX power and RX sensitivity compare to the switched design?
3. Are the TX/RX impedances for UFBGA73 available to design a direct-tie network per AN5457?

Thanks!