Obtaining less then 50uA with 52840 dongle and PPKII

[androbi]

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!

[Simonr]

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

[androbi]

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.

[androbi]

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.