Hi,
With several nrf52840 based prototypes, I had serious problems. I could see them die after flasing them a few times. And this was not just one dying, it was all of them, and never the first time. Sometimes after a few weeks.
After investigation, I noticed I was not connecting VDDH to VDD ( I use a 3.3 v li bat ). I thought it was not a requirement if you don't use VDDH but just VDD.
I modified the design, had new prototypes built, and the problem seems now to be gone.
What do you think? Do you confirm that was the reason? and why this happens?
Thanks in advance
Mau