power measurement of system_off app on nRF54-DK

[bios-bob]

i've captured the following using a joulescope js-220 as an inline current meter across the VDDM CURRENT MEASURE jumper on my rRF54-DK board....

i'm running the system_off sample app, with the GRTC configured for a 2Hz wakeup....

per instructions in the docs, i don't have any open serial ports or attached debuggers....

now, take a look at the 85uJ consumed in the pink region -- consistent with an active system....

what i can't explain, however, is the 69uJ consumed in the green region -- which subsumes the pink region....

indeed, the blue region reports -8uJ over an interval when the system is off....

is there an explanation for what otherwise seems too good to be true ???

[Simonr]

Hi

So, this could be the capacitor on DECD that's charging up. Here's a plot from the power profiler kit waking up and advertising once before going to sleep again, as I assume your device is also waking up here and turning off again.

When the nRF54L wakes up,the DECD capacitor is being charged from 0.7V to 0.9V so you get an inrush current on it. The same amount of energy will be saved after the event when it goes back down to 0.7V, so I think what you're seeing could be realistic without going into the nitty gritties. 

Best regards,

Simon

[bios-bob]

i switched to the button-press version of `system_off`, and simply let the board sit in SYSTEM_OFF indefinitely....  measuring current now, everything stayed flat at -6uA....

assuming i'm consistent with this configuration from the user's guide:

will i ever see this number on my nrf54-DK???