Current reach 100mA when using nrf21540 FEM

[Ziyao Zhou]

Hi,

I have two nRF52833 DKs and both of them has connected to nRF21540 EK. I set the transmitter sending out 244 bytes data without stopping and measure it's current. The setup is like below and the average current is around 60 mA at 1.8V

 ...

When I plug out the antenna of the transmitter, the currrent reach up to 100mA.

I have no clue about this, as I expect the power has no relationship with antenna. As in both case the FEM is using, only change is RSSI, and RSSI both are at same level. First time is -19, second time is - 24

[ketiljo]

I have no clue about this, as I expect the power has no relationship with antenna

The PA is designed for a 50 ohm load. When you unplug the antenna, there will be severe missmatch since the impedance the PA sees into the connector is very high. All power that's sent into the antenna is reflected back into the PA when there's no antenna presen. You may damage the device if you operate it without the antenna.

[Ziyao Zhou]

Thank you so much for your information!