nRF9160 DK PA characteristic

[Nik8]

Hello, 

I am analyzing the DKs power amplifier characteristics as an assignment for university. 
I got the serial_lte_modem running and send AT commands via UART from an external micro controller, which works fine. 
The board is powered with an Otii to measure the current, as described here Otii connection and I don't have a micro USB cable connected to the DK. 

I use the RFTEST (tx testing) for analysis, configured to send continuous wave signals, e.g. like this: AT%XRFTEST=1,1,8,9000,15,0,4,0,0,0,3,0,0\r\n. 

My question is, what consumes power when using the RFTEST or whether it's mainly the PA?
I send a CFUN=0 command beforehand and thereby get a base line current of 750 uA.
For the RFTEST example from above, with a voltage of 3.7V, I get a current of 101mA.

Also, is there any information available on what PA class the used PA belongs to?

Thanks in advance! 

[Heidi]

Hi!

RX and TX have a baseline consumption of around 40 mA that's constantly pulled from VDD1 during sending/receiving. Then you have the PA on top of this that pulls from VDD2 to boost the TX output effect. If sending on 23 dBm, you might get around 400 mA extra being pulled from the PA. But this also depends on the output effect.

As for the PA class, I don't believe this is documented anywhere but I will ask the HW developers for this information.

Best regards,

Heidi

[Nik8]

Hi,

thanks a lot for the fast reply and the further enquiry on the PA class.

I have one follow up question.
Are the 40mA baseline consumption applicable for all possible supply voltages (e.g. 3.3V or 5V) or only for 3.7V?

Best regards, 
Nik

[Heidi]

Yes, the approximate baseline of 40 mA is for all supply voltages. 

As for the PA class, per the nRF9160 PS, the transmitter power class is 23 dBm nominal, which is Power Class 3 in 3GPP terminology. 

The specific PA class in the nRF9160 SiP is not external information. 

[Nik8]

Ok, everything resolved then, thank you!