Softdevice high idle state power consumption

[Aamir]

Hi, 

I am using nrf52840 Preview - DK, with SDK v15.3.0 and Softdevice API 6.1.1

I have modified the 'ble_app_blinky' example to have an advertising interval of 500ms and turned off the NRF_LOG by setting the NRF_LOG_ENABLE and NRF_LOG_BACKEND_URAT_ENABLE to 0 in the sdk_config file.

I have measured the current using an ocsilloscope and I am not getting the idle current (3 uA)a s described on the online power profiler, I entered the the following parameters in the online power profiler 

nrf52840, voltage 3, DCDC off, internal RC, Radio power 0 dbm, advertising(connectable), Tx payload: 31 bytes.

also we have not connected the oscilloscope  in the manner shown in the documentation, but we used one probe and connected it one pin of nrfCurrent Measurement and the other one to it's ground (reference). because when we were connected it in the manner shown in documentation we were not able to see the waveform. 

Please, tell me how can I achieve 3 uA idle current consumption. 

scope_5.scp

I have attached the '.scp' file that has the respective readings

[Aamir]

This is how we have connected the oscilloscope. 

[Stian Røed Hafskjold]

If you are connecting the scope like this you must be sure that ground on the scope is not connected to the same ground as the development kit. Otherwise you will short the USB power / power supply to ground.

I can't open the scp file. Which program do you use to open it?

So what is the idle current you measure?

Which value do you use on the measurement resistor?

Try to connect an amperemeter/multimeter on the measurement header (remove the resistor) instead of the scope. It's easier to setup and you can use it as a reference for your scope-setup.

[Aamir]

We can see the TX, RX waveform of the BLE.

I don't know how to open the file either, the oscilloscope saves it by default in that file

We can see over 200 uA in idle 

we use a 10 ohms resistor.

[Stian Røed Hafskjold]

Can you try to flash the hex file located in the ble_app_pwr_profiling example folder? It starts in system OFF, so it will consume less than 1 uA. If you still see several microamps, then there's something wrong with the measurement setup.

Then follow this setup:

• Supply power to the P21 "external supply" header (3V).
• Set SW10 (VEXT->nRF) to the ON position
• Cut SB58 (on DK version 1.0.0 or newer)
• Keep USB cable plugged in
• Set SW6 to nRF ONLY
• Set SW9 in VDD position
• Measure current over P22

[Aamir]

Hi, 

I flashed the ble_app_pwr_profiling hex file and we were getting several hundred microamps.

Then I followed the steps you laid down, except cutting SB58 because my DK version is less than 1.0.0, I think, the sticker on  DK  says PCA10056 V0.9.2 2017.26 (please confirm that this is less than version 1.0.0)

after following your given steps, now we are reading current consumption of around 50 uA

I have attached the images of oscilloscope and setup here

 

[Stian Røed Hafskjold]

Yes this is less than version 1.0.0

Can you try to measure with a multimeter instead of the scope?

So is the 50 uA based on the 290uV RMS value? You have to use average value, not RMS.

Are you sure the accuracy of the scope is in the uA range?

[Aamir]

the RMS value is fluctuating quite frequently, the moment I captured the above picture it was showing 290uV but it mostly remains aroung 500uV that is why I said 50 uA

We measured it with multimeter and we got around 270 uA 

and on the oscilloscope, we switched to Average and the value is fluctuating very much it is even going into negative values

[Stian Røed Hafskjold]

Are you sure that the ground potential on the scope is completely isolated from the DK? Did you try with a multimeter?

[Aamir]

Yes, the ground on scope is isolated from DK

and we measured it with a multi-meter, we got around 270 uA