It is possible to power the System on Chip (SoC) directly from a source without powering the rest of the Development Kit (DK) from the same 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, and the allowed voltage range is 1.7–3.6 V.
Since it is only the nRF52833 SoC that is supplied from this source, it is recommended that the VDD domain is supplied from a different source to prevent the pins of the SoC to be 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 to be present on 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 Firmware development mode.