High sleep current on nrf52840

[jonram]

On nrf52840 I get a current of ~10 uA while sleeping. At the moment I don't run any code and don't start up the softdevice. I go directly to sleep with __WFE(). The result with the same code on nrf52832 is ~1 uA. Any suggestion on what the reason is and how it can be resolved? 

[Susheel Nuguru]

Can you tell give me the laser markings on your chip and the project that you ran on this chip. I need to see the startup files before main.c to see if they are doing some errata workarounds 

[jonram]

Chipmarking:

N52840

QIAAC0

1806AB

First SystemInit() from nRF5 SDK v15.0.0 is called. After that the the only piece of code I use is the row below. It is located in _start() which is called by the reset handler after SystemInit():

while(1) {__asm volatile ("wfe");}

for nrf52832 I use SystemInit from system_nrf52.c

for nrf52840 I use SystemInit from system_nrf52840.c

[Susheel Nuguru]

I did a quick test on my desk with that same revision chip. Using a power profiler kit the average current for nRF52840 shows 2.3uA.

What are you testing this on? is it a PDK or your own custom board? 

[jonram]

I have tested both on our own board and the PDK with the same result. The PDK was supplied through external supply pins.

This was used for measurements:

https://www.qoitech.com/

[Susheel Nuguru]

please send me your whole project so that i can test exactly with what you tested and can see the difference.

[jonram]

We found the problem.

We supplied voltage on VDD.

VDDH pin was connected to VBUS, but not to supply voltage.

Supplying VDD and VDDH and let VBUS float gave us the correct current.