Obtaining less then 50uA with 52840 dongle and PPKII

RE: Obtaining less then 50uA with 52840 dongle and PPKII

androbi — Mon, 03 Jan 2022 21:10:17 GMT

I just wanted to come back so this case can be closed. I got a new unit of the PPK2 and it works as expected, I am now getting uA (see PD) readings without noise for the dongle. Definitively my first unit is not doing well in the low current ranges. It was not easy to find out as the unit seems to be working but gives wrong readings, probably due to noise present in the sensitive circuits.

PD: I could only get down to 12uA for a zephyr "sleep only" app. I would be interesting to find out why this is not lower. If I find something out I'll report in another thread.

RE: Obtaining less then 50uA with 52840 dongle and PPKII

androbi — Tue, 21 Dec 2021 10:04:48 GMT

Hi Simon, as I wanted to exclude the "unknown" of the dongle power consumption I switched to resistors as loads which have a defined behaviour. Yes of course I have visited the link you cite, I have tried with hub and without hub, with different usb cables and on 2 different computers (albeit both LG Gram models), all to the same avail. I still might try my old laptop which is already retired, but which worked great with the PPK when I bought it. I will give it a try before opening the device then.

RE: Obtaining less then 50uA with 52840 dongle and PPKII

Simonr — Tue, 21 Dec 2021 09:56:08 GMT

Just for confirmation, did you test the .hex files I sent you on your Dongle and what current consumption did you see when running that example?

Unscrewing the screws will not void any warranty. Did you at all go to the link reported by the power profiler on GitHub? It should explain some common errors with data loss. I discussed this issue with some colleagues as well, and the data loss you're seeing might be caused by communication issues over USB, so you can try with another computer if you have one available to see if you get the same results there. The PPK is not necessarily malfunctioning, just the USB on your PC having issues.

Best regards,

Simon

RE: Obtaining less then 50uA with 52840 dongle and PPKII

androbi — Mon, 20 Dec 2021 13:52:01 GMT

Of course we can never 100% exclude the possibility of a wrong setup, but I have been using the unit very carefully. I usually only operate it in source mode or with a max. 4.2V Lipo in amperemeter mode, so a too high voltage can probably be excluded. As I commented above, the unit still works (sourcing and sampling) but not in the lowest uA scales, the failure of some of the components (op amps for low uA input?) could certainly also be a possibility. Would you like the photo with the device closed or opened so you can see the components? Please confirm in this case that opening does not void the warranty. Kind regards, Claus

RE: Obtaining less then 50uA with 52840 dongle and PPKII

Simonr — Mon, 20 Dec 2021 11:36:56 GMT

Unfortunately, these values seem strange indeed, and it looks like your PPK is damaged indeed, and it has likely been subject to an incorrect setup or too high voltages somehow. Can you upload a high resolution picture of your PPK so we can take a look at it?

I have asked one of our other PPK experts for a second opinion as well as I'd like to make sure before declaring your board as broken beyond repair, but they're out of office until 3rd of January, so the conclusion will take a while. Thank you for your patience

We will be short on staff during the Holiday period, and delayed replies must be expected. We will be back to full staff on January 3rd. Happy holidays and happy new year!

Best regards,

Simon

RE: Obtaining less then 50uA with 52840 dongle and PPKII

androbi — Sat, 18 Dec 2021 10:01:55 GMT

I have reloaded the firmware and have run some more tests in both modes. The device seems to work in the mA range (3.5 V battery and 220Ohm resistor give me 15.9mA) but there is quite a strong noise present in the signal:

With a 47K resisitor (which should give around 75uA with this battery) I get the same current as without a DUT connected (which is a 20 uA mean value noise floor). The noise floor consists of 2.5mA (and a few 4.9 mA) random spikes with a (colored) noise distribution in the power spectrum. Also note the "Data loss detected" messages in the log.

Do you think it would be possible to fix this this or do I need to get a new device? I am not aware of having produced a short circuit or having exceeded the max. current so I wonder how this has happened.

RE: Obtaining less then 50uA with 52840 dongle and PPKII

Simonr — Thu, 16 Dec 2021 13:35:50 GMT

Oh, that's unfortunate. First, please try reload the application firmware on the PPK2. For example by opening the nRFConnect Programmer app and choose the PPK2. This should put it in bootloader mode, which will trig a request when you open the power profiler app next time to flash the Power profiler firmware onto the board again.

Next, I would suggest using Ampere mode to measure current. I generally find it easier at least. Source meter is supposed to be used to power the board with the PPK as a power source.

Best regards,

Simon

RE: Obtaining less then 50uA with 52840 dongle and PPKII

androbi — Wed, 15 Dec 2021 21:00:49 GMT

I think I can confirm that the PPK2 is not working correctly. It still sources the correct voltages but the sampling must be crippled somehow. I have used a 12k Ohm resistor as a load to get in the mA range but the current was not detected (still showing uA). Given that it is out of stock everywhere this is really bad news :( Is there any reset routine that I could try?

RE: Obtaining less then 50uA with 52840 dongle and PPKII

androbi — Wed, 15 Dec 2021 20:26:03 GMT

I have literally erased SB2 and the results stay the same. This is when I suspected that my PPK2 might be not working correctly. I should be able to obtain approx 3-4uA with a Lipo or by sourcing 3-4 V from the PPK2 and using a 1MOhm resistor, right? I get very noisy results and can not observe Ohms law.

What woud be a correct way to check the PPK2? I have noted quite a few "Data loss detected" messages that I think did not show up before.

RE: Obtaining less then 50uA with 52840 dongle and PPKII

Simonr — Wed, 15 Dec 2021 11:36:10 GMT

Hi Claus

This looks good indeed. Please double/triple check that SB2 is cut properly, so that there isn't any leakage over VBUS_nRF. There's been a case or two in the past where we've discovered that SB2 was actually drawing some current. You can also try measuring over SB2 to make sure that no current is drawn.

If you're still seeing too much power drawn, it might be an issue in Zephyr and you can try flashing this ble_app_pwr_profiling (and SoftDevice S140) onto the Dongle to see if that lets you get lower.

devzone.nordicsemi.com/.../5808.ble_5F00_app_5F00_pwr_5F00_profiling_5F00_pca10056_5F00_s140.hex

devzone.nordicsemi.com/.../s140_5F00_nrf52_5F00_7.0.1_5F00_softdevice.hex

I see that I didn't change the name of the .hex file, but the project should be modified to work on an nRF52840 Dongle.

Best regards,

Simon

RE: Obtaining less then 50uA with 52840 dongle and PPKII

androbi — Tue, 14 Dec 2021 20:23:22 GMT

Here you go! When measuring with the PPK2 as source I connect PPK2-VOUT to the "VDD OUT" pin on top (which is connected by the red cable to the dongle's VDD-OUT) and PPK2-GND to the GND pin on the lower right. When using amperemeter mode, I connect PPK2-VIN to BAT+ (which is connected to the battery below), PPK-VOUT to the upper VDD OUT pin and PPK-GND to the lower right GND. The battery - is soldered to the GND pin on the lower left.

Normal operating mode is simply to shorten BAT+ and VDD OUT. The cell gives 3.020V.

In case you have doubts about my soldering skills - which I do have :) - I have also connected PPK2-VOUT directly to the VBUS pin and PPK2-GND to the GND next to it on another unit which does not have the SB2 cut and SB1 soldered. In this case I got 35uA at 5V.

RE: Obtaining less then 50uA with 52840 dongle and PPKII

Simonr — Tue, 14 Dec 2021 08:12:08 GMT

How exactly are you connecting the PPK2 to the Dongle? I agree with Stian that you should be able to get down (or at least close to) 2-3uA. Maybe you could upload a high resolution picture so we can take a look at how the PPK and Dongle is connected.

Best regards,

Simon