nRF9160-DK interface MCU extreme heating and generates error 33 when flashing

[GPO]

Hi Everyone,

My issue is mostly stated in the subject, I hope someone can help me recover this DK because as of the moment this is my only way to program/debug out EVT board for our current product, thank you in advance.

BR,

George

[Øyvind]

Hello, 

How have you configured the DK switches? Are you connecting with USB? What is connected to the DK ? 

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Please note that we are currently in our summer vacation period and responses are expected to be slow due to little availability of resources.

Kind regards,
Øyvind

[GPO]

Hi! Thank you for this reply. The only switch I changed since I received this DK was the VDD IO to 3V because our EVT board is 3V. What I noticed though is when VDD IO is at 3V, the actual voltage on DK's VDD will be 2.8V while my EVT board is still 3V. Yes, its USB connected directly or via USB hub because I'm working with a MacBook. The only connected to DK is the EVT board, nothing else. What is strange is I already was working with this setup with no issues, but starting yesterday afternoon, I get an error when doing west flash, and when I investigated more, I realized that the interface MCU of the DK was extremely hot. I already tried two EVT boards but still the same. 

[Øyvind]

What happens if the EVT board is not connected? How have you connected it to the DK?

What version of the DK are your using?

Thanks.
-Øyvind

[GPO]

If EVT board is not connected and the VDD IO is at 3V, the interface MCU will keep heating. But if I set VDD IO is at 1.8V, it still heats up but bearable. Also I can program the onboard nRF9160 with no issues. I only connect the VTG, SWD IO, and SWD CLK from P20. Then I use GND from P13. Im not sure where to find version but does "PCA10090 0.15.0 2020.42" help?

[GPO]

Btw, let me describe how I was debugging before this issue happened. The EVT board is powered by a battery, then I am investigating the behavior when battery is depleted and plugging the USB to the EVT board for charging. Note that VTG pin is constantly connected to the EVT boards VDD while battery is charging via USB, then discharging by unplugging USB and kept LED ON until battery will deplete. With this process, will this affect the interface MCU (U4)? If yes, can it still be recovered?

[Øyvind]

Thanks for providing this information. 

Has the EVT board been through HW review by any of our engineers? Please provide HW schematics, and an overview of how the two boards are connected.

Are you seeing this issue if the EVT is not powered by battery? What kind of output does the battery charging circuit provide? 

Will discuss with our HW guys.

Kind regards,
Øyvind

[Øyvind]

If no external board connected, does the interface MCU get as hot?

-Øyvind