nRF7002 RFBUCK VDD voltage

[rolandash]

Dear Nordic,

I am debugging a custom hardware with a nRF7002 on-board, using wifi shell app. At this moment the shell does not work as expected, needs to locate where the problem is.

The nRF7002 is supplied with 3.3V VBAT, and 3.3V IOVDD through an external switch. The GPIO controls the switch seems working, as I can measured about 3.33V on IOVDD pin, and the BUCKEN signal as well. When I check the output voltage from internal BUCK on RFBUCKVDD pin, the voltage is about 1.48V. 

I had an impression that I read somewhere before that the proper voltage of this RF BUCK VDD should be around 1.6V, but I can not find it again in documents anymore. Can you please help to confirm what should be the proper voltage on RFBUCKVDD pin? Does 1.48v look normal?

Thank you.

/Roland

[Elfving]

Hi,

I am not so sure if what you describe is a problem.

In what way is the shell not working? What NCS version is this? Are you seeing it working on a DK? Since this is a custom HW I guess DTS could be a potential issue as well. Is everything else working on this board?

Have you gotten the hardware and layout reviewed by us before?

Regards,

Elfving

[rolandash]

Hi Elfving,

The 'Wifi Scan' command failed. My current inspection shows the init process is blocked waiting as no response from nrf7002 reading RDSR2 through QSPI bus.

No I did not send the hardware and layout for review before, as the design and layout are pretty much the same as the reference circuit so not much to talk it about I think.

I can run other example apps well in this hardware, as long as there is no Wifi get involved.

I agree that wifi related DTS could be a potential issue. Before I dive even deeper into the software and QSPI protocol part I just like to make sure first that the wifi chip is in a normal status.

The main power supply seems fine, and the power-up sequence seems also working, and the frequency of OSC looks good as well. however RF BUCK VDD looks bit drifted from what in my memory. As this voltage characteristic seems missing from documents, so can you please confirm what is the normal value of this voltage and if the measured 1.45v in range?

Thank you very much!

/Roland

[Elfving]

rolandash said:

As this voltage characteristic seems missing from documents, so can you please confirm what is the normal value of this voltage and if the measured 1.45v in range?

Yeah that doesn't look like a problem to me. 

One usual suspect is the powering sequence, so it is good to hear that you are aware of it. 

rolandash said:

I agree that wifi related DTS could be a potential issue. Before I dive even deeper into the software and QSPI protocol part I just like to make sure first that the wifi chip is in a normal status.

Having a look at the lines with a logic analyzer might also be helpful, to make sure that there is something going on on the lines.

rolandash said:

No I did not send the hardware and layout for review before, as the design and layout are pretty much the same as the reference circuit so not much to talk it about I think.

Either way it might be worth having a look. I can make the case private if you like, so that only you and Nordic employees can see what is being shared here.

Regards,

Elfving

[rolandash]

 Elfving 

Thank you for the confirmation. 

This is important, as hardware fault may not only come from wrong schematic or layout issue, but may also comes in from SMT process or PCB manufacturing, which is, in my view, more difficult to locate as these usually are not as visible as other problems. 

The inspection into QSPI protocol may take up to tens of hours work so I do not want to invest blinded before I can exclude these problems as well.  Since now I have your confirmation I think I can continue down the path now.

So far the problem is still at very early stage of the WIFI bring-up process, even the WIFI firmware not been loaded, so the debug context on hardware is quite simple as it only involves QSPI bus. I think I may need your further help when I am able to talk to 7002 and start to tuning radio performance. 

/Roland