TX power has strange relationship with overall power of chip

[Ziyao Zhou]

I designed a PCB with only the nRF52833 chip and antenna. I want to learn about the relationship between different TX power levels and the overall power consumption of the chip.

I am using a power profiler with a 1.8V supply and reading the average current via software.

During the tests, the TX RX position remains fixed. I obtained the following results:

Why is the received signal strength higher when TX power is 0 dBm compared to when TX power is 4 dBm? Why does the overall power consumption increase when the TX power is reduced to negative values? I look forward to your response.：）

[Simonr]

Hi

First off, please show us how you're doing the power measurements here on your end. It seems very strange that the system power won't decrease the lower the TX power here is, so please provide some details on what the application is doing (just advertising a beacon, or connecting to a central device for example). What software is running on the nRF52833 here when testing on your end?

I think the RX RSSI isn't the best way to measure anything here, as RSSI is very volatile and dependent on the test environment to be very stable to give good results. You can use the Online Power Profiler for some estimates of what is expected at the various radio TX powers:  Online Power Profiler for Bluetooth LE  

Best regards,

Simon

[Ziyao Zhou]

Hi Simonr,

Thank you for your response! I am using my self-designed nRF52833 as a peripheral device to send specific fixed 44-byte data. An nRF52833 development board is used as the central device to receive the information and print the RSSI.

During the test, the positions of both the TX and RX remained unchanged. The only variable modified was the TX power on the TX side, which was adjusted through the software. Why do these two counterintuitive results occur?

Regarding the calculator you mentioned, I will learn about it. THANK YOU!!!

[Simonr]

Please also share some details on how you're doing current measurements on your end.

Best regards,

Simon

[Ziyao Zhou]

Hi, I use the Power Profiler Kit II to supply 1.8V voltage and read the average current to calculate power consumption.

[Simonr]

Can you upload the .ppk files you've done here so we can review them making sure that the current consumption graph looks as expected?

Best regards,

Simon

[Ziyao Zhou]

Hi Simonr，

I use PPK to get the average current in 10 seconds (the windos) and then mutiply the current and voltage to get power. Is that OK?