It is possible to power the application System on Chip (SoC) directly from a source without powering the rest of the Development Kit (DK) from that source.
This is done by connecting the external source to the external supply connector (P21) and sliding the VEXT->nRF switch (SW10) to the ON position. The nRF power source switch (SW9) must be in the VDD position. The allowed voltage range is from 1.7 V to 3.6 V.
Since only the nRF5340 SoC is supplied from this source, it is recommended that the VDD domain is supplied from a different source to ensure the pins of the SoC are not connected to unpowered devices.
To avoid voltage differences on the DK, the external supply is also connected to the input of the voltage follower when the VEXT->nRF switch (SW10) is in the ON position. The voltage follower circuit requires 5 V supplied to the DK, see 5 V power sources.
The voltage follower can be disconnected from the External supply by cutting SB58. To prevent leakage due to voltage differences, the DK should be set in the nRF only mode, see nRF only mode.