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Obtaining less then 50uA with 52840 dongle and PPKII

Hi,

after fixing a missing ground in my setup (see devzone.nordicsemi.com/.../interaction-jlink-and-power-profiler-ppkii) I have not been able to get less than 50uA of idle current on the 52840 dongle, when it should be around 2-3 uA. My main.c is

#include <zephyr.h>
#define SLEEP_TIME_MS   10000
void main(void)
{
	while (1) {
		k_msleep(SLEEP_TIME_MS);
	}
}

and I use CONFIG_SERIAL=n in prj.conf. I guess I have read almost all posts here on the forum about low power modes, but I could not find anything similar. I have tried the PPKII in source and in ampere meter mode (using a 3V battery), the USB is not connected and power is supplied using VDD Out pin with SB2 cut and SB1 soldered. I have measured with the debugger disconnected and done a power reset after disconnecting. All with the same result, around 50uA of mean current at 3V.

When using source mode on the PPKII I can drop the voltage to 1.9V and then I get around 15uA. Why should the current drop with the supplied voltage?

From the schematics the 52840 dongle does not have any passive elements which could source current (apart from the leds and , so I'd suspect power consumption coming from the SoC itself. But I have even measured 50uA @ 3V using

pm_power_state_force((struct pm_state_info){PM_STATE_SOFT_OFF, 0, 0});

which should be the lowest power mode possible. I am really stuck with this, any help appreciated!

  • Hi

    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

  • 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.

  • 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

  • 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

  • Hi

    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

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