NRF52840 too high systemOFF current

[jonas.woerner]

Hi,

I am trying to get my systemOFF current below 1uA, but Im struggeling.

normally I use MBED, but to eliminate that variable, I just did a test without MBED, I took the nordic blinky example(SDK15.0) and added

sd_power_system_off();

to the

BLE_GAP_EVT_DISCONNECTED

so, when I connect and disconnect, the current drops from about 1mA to 36uA. This is exactly the same behaviour as I see on my application running with MBED.

So, its not MBEDs fault, so it must be mine.

what am I missing out?! I have searched through all of the posts about the systemOFF mode drawing too much current, but none of these problems were like mine.

Is it possible, that its because I am using an preview-DK? I have read all the errata about the first revision of the NRF, and didnt find something similiar to my problem.

thanks,

Jonas

[Simonr]

Hi Jonas

What are you using to measure the current? If you are measuring over the current measurement header and powering the board with USB, my guess is that this extra current is USB interference.

Best regards,

Simon

[jonas.woerner]

Hi,

yes, I am measuring with the PPK and USB as power supply, but that cannot be the isssue, as I am able to get the current down below 1uA, by creating an empty program with just NRF_POWER->SYSTEMOFF = 1 in the main function.

are you able to reproduce my issue created with the blinky example? maybe on a preview DK vs release DK?

anyways, I will order a new DK and continue testing with it.

thanks.

[Simonr]

Hi Jonas

Due to the Easter holiday, we are understaffed and I cannot prioritize this request, as it still seems to fit the bill with USB interference. I can get back to you next week if you still want me to test this. Sorry for the inconvenience!

Best regards and happy Easter,

Simon

[jonas.woerner]

no problem, just test it whenever you have the time.

I just tested a few different things:

first I tested it with battery DUT supply instead of USB, but no change.

then I took one of the PCA10059 sticks and wired it up to the PPK, strangely it draws way more power than the DK does, why is that?

It draws about 100uA in systemOFF. does it have any peripheral that draws power that im not aware of?

so I still dont have a clue on whats going wrong...

[Simonr]

Hi Jonas

The Dongle runs in high voltage mode by default. I am guessing this extra current draw is due to the Dongle using the internal REG0, which has some quiescent current drawn from VBUS. You could try using an external regulated source instead to make it run in normal voltage mode. This link explains how.

Best regards,

Simon