STM32WL: Can you damage the microcontroller by transmitting without a load?

[AJ_1]

Hi All,

When dealing with RF transmitters, it's common advice to always put a load on a transmitter before turning it on, because running it with no load can break it. I'm curious if that applies to STM32WL microcontrollers as well. If I transmitted a wireless packet and accidentally left the RFO_HP pin disconnected (open termination), will that damage the microcontroller? Or does it have some way of protecting itself? Does damage only occur if you output above a certain power level?

I read the errata and learned about the TxClampConfig register. I'm curious if that comes into play at all.

[STTwo-32]

Hello @AJ_1 

I didn't test this case, but I think you should always follow this recommendation to keep safe your device from any possible issue. 

Best Regards.

STTwo-32

[AJ_1]

Hi @STTwo-32,

In my design, I am only using the low-power transmitter. Since I don't need the high-power transmitter, I'm planning to leave that pin open and disconnected. If the microcontroller code accidentally transmits using RFO_HP instead of RFO_LP, it will be an un-terminated transmitter.

It sounds like the outcome of this situation is unknown.

Can you tell me more about the TxClampConfig register (address 0x08D8), beyond what's in the datasheet/errata/reference manual? The existing documentation doesn't go into much detail about it. How does it know when to clamp the output power? How does the setpoint convert to a clamping level? What range can it be set to?

Thanks!