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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!

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  • 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.

    5808.ble_app_pwr_profiling_pca10056_s140.hex

    s140_nrf52_7.0.1_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

  • 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.

  • 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?

Reply
  • 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?

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