nRF5340 behaves like LDO mode while DCDC mode is configured

[Ben_Squar3d]

Hi,

We are facing a strange behavior where the consumption we measure on the nRF5340 doesn't change according to supply voltage like it is supposed to do in DCDC mode. 

This behavior seems to indicate the nRF5340 is running in LDO mode, but the registers shows that we are supposed to be in DCDC mode : 

Our wiring diagram is the following (same as product specification v1.6, chapter 9.3.1 Circuit configuration no. 1 for QKAA aQFN94) : 

We need help to understand this behavior. 

Thank you very much

Best regards

[Kenneth]

Hello,

I can see you are debugging, in debug mode the chip will stay in LDO mode, this to ensure that programming and debugging can occur even when there is no DCDC available. I suggest you do a hard reset (power cycle) and measure the current then.

Kenneth

[Ben_Squar3d]

Hi,

Thank you for your quick answer. The consumptions are mesured in release mode, not debug mode. How to verify the values of the register without being in debug mode?

[Ben_Squar3d]

Kenneth said:

The first radio spike you are focusing on can be explained by

All the spikes are around 14mA, not only the first one. This value is typical from the LDO configuration shown in the profiler.

I did measurement with LDO enabled, and the results are almost the same : BLE spikes are around 15mA and does not change according to supply voltage (same case as before, but now consistent with profiler estimation), but the floor consumption increased from 150uA to 400uA.

Output voltage is set to 1V8.

[Kenneth]

I can try to measure myself next week on a DK for comparison.

I was thinking that the green peaks are not that far off the online profiler:

And that the red spike is caused by either:

- measurement error due to ppk change measurement range from <5mA to >5mA
- transient due to charging of C31 (will likely occur in both LDO and DCDC mode)

If you say that you see no difference in the green spikes when going from DCDC to LDO, then it sounds like it's something else problematic here that we can't see. The schematic looks good as far as I can see. 

Next step would be to try a simple BLE beacon example from the SDK for comparison, that should be able to run on any hardware.

Kenneth

[Ben_Squar3d]

Okay, I misunderstood what you meant by first spike sorry, This diagram comes from a collegue's measurment so I made other measurments with another device. Here is the diagram: 

While the spikes are still around 12mA like the others, the profile is different. So I took the total average current from the profiler (11 µA ) and compared it with the average current I had on my device : 13 µA. knowing that I have an external flash consuming 1µA so in term of energy, I think we are good. You might have right about the ranges switch of the ppk, leading to wrong spike values. 

Knowing that floor consumption jumps about 250µA when enabling LDO instead of DCDC, I think we can say that the nRF5340 is actually in DCDC mode.

Kenneth said:

Next step would be to try a simple BLE beacon example from the SDK for comparison, that should be able to run on any hardware.

I just wasn't able to make wthe beacon sample work for our custom board nor 7002dk. The ipc_radio.bin won't build, and I got err -11 from bt_enable(). Could you give me the right build configuration to make it work please? It is still good to verify with a minimal example. Thank you very much

[Kenneth]

Hi,

Thanks for the update. Looks like to be a PPK issue yes.

Ben_Squar3d said:

The ipc_radio.bin won't build, and I got err -11 from bt_enable().

What ncs version you are using? I would expect this to work out of the box, do you build from command line or vs code? I assume you are using sysbuild? Error -11 from bt_enable() normally means that the network(radio) core is not programmed, which make sense seeing that you have problems building radio core.

Kenneth

[Ben_Squar3d]

I tried both Build system default and Use sysbuild option. I tried to not include ipc_radio.conf and by including this file.. I tried prj.conf and prj_coex.conf... Nothing seems to work. I think I am missing something, but it's been a year I didn't struggled on build issues so I don't remember the black magic behind it.

Thank you for your help