Operate nRF52840 PDK version 0.9.0 at 1.8V VDD while debugging

Hello,

I would like to use the nRF52840 PDK version 0.9.0 at 1.8V VDD since my peripherals operate at 1.8V. At the same time, I would like to debug the DK through USB.

I followed the corresponding section in the manual and completed these steps:

  • 1.8V external voltage connected to P21
  • VEXT->nRF switch is in the ON position
  • USB connected on J2
  • SW9 on VDD
  • SW6 on default

Nevertheless, I still measure a VDD voltage of 3V at P1.

While searching for an explanation, I noticed a difference in the schematics between DK version 0.9.0 (which I use) and the more recent versions. 

In version 0.9.0, VDD_nRF_SENSE is not connected to SW10.

In the more recent versions, VDD_nRF_SENSE is connected to SW10.

Could this be the reason that the VDD voltage stays at 3V instead of going to 1.8V as expected?

Thank you for the help,

Sebastian