Strange idle current consumption

[Igor]

We have a custom device that we profile with a PowerProfiler (external DUT). Device is battery powered. 

We have a strange idle current: cca 5 uA for 2 min, then 900 uA (!) for 2 min, 5uA 2 min etc... 

Why there are so much current fluctuactions? (900 uA is a huge current.) How can we find out what is going on? Is there any whay to detect what happens when idle current changes?

[SDK 15.2, SD 6.1, nRF52840].

[Simonr]

Hi Igor

It is hard to find out without knowing your code or custom chip. But always when having problems with custom boards can you try the same software on a development kit or similar, so we can find out if the problem is with the hardware or software. Also, if you are using the timer STOP task, there is errata on that particular task causing the nRF52840 to draw excess current. Can you check if this might be the reason for your current draw?

Best regards,

Simon

[Igor]

Fixed.
It turned out to be related to SAADC with oversampling. Oversampling produces multiple measurements. CPU won't enter into sleep mode until all measurements are consumed. So, if this (accidentally) happens, current may be unusually high.