nRF21540 with no load

[Rashid Talib]

Hi

Is there a specification of running the nRF21540 in Tx mode at 10 dBm and 20 dBm with no load connected? Will the reflected signal cause damage to the PA and if yes, do you have a suggestion to protect the chip against it?

Background: We develop a module using the nRF5340 and nRF21540 with an SMA antenna. If the user removes the antenna during Tx mode, we need to be sure the module will not be harmed.

Thanks & best regards

Rashid

[Hieu]

Hi Rashid,

After some internal inquiries, we concluded that there is risk of damaging the FEM if it is run unloaded for an extended period of time. 

There is unfortunately no way to protect against this without sacrificing RX sensitivity.

Perhaps it's best to make sufficiently clear warning against this misuse?

Best regards,

Hieu

[Rashid Talib]

Hi Hieu
Thanks for your reply. If RX sensitivity could be compromised, what solutions would you suggest?

Best regards
Rashid

[Hieu]

Hi Rashid,

I double checked with my colleague, and it's not just RX sensitivity, but both TX and RX performance need to be compromised, by adding an attenuator between the FEM and the antenna. I must stress that this is not a good solution though, as it is just wasting power/.

Best regards,

Hieu