Antenna Port Protection Measures

[joey]

HI,

I’m working with the nRF21540 and want to add a GDT, a series capacitor and a TVS diode to its antenna port to protect it against lightning surges and ESD. Could you recommend proper component models or the key points to note for this design?

Thanks!

[ketiljo]

Just make sure the TVS diode is of a low capacitance type so it doesn't load the antenna. Series capacitor at 100 pF will have little impact. 

[joey]

Thanks for your reply.

1、Do gas discharge tubes (GDTs) have the same requirements as TVS diodes?

2、Are there any recommended models, and how should the clamping voltage be selected?

3、Are there any specific guidelines on the selection of these components?

[ketiljo]

1. I would think that the capacitance of this is very small, but check the datashee

2. No recommended parts here. The pin is already internally protected so the clamping voltage doesn't really matter as long as it's higher than the supply voltage. 

3. Not really. For the diode, less than 0.1 pF would have little impact. 

[joey]

What is the operating voltage of the RF port of the nRF21540, and what is its maximum safe voltage?

[ketiljo]

To dissipate 20 dB or 100 mV into a 50 ohm load, you need a voltage of 2.2 Vrms, or 3.2V peak.