It is possible to power the System on Chip (SoC) directly from a source without powering the rest of the Preview Development Kit (PDK) from the same source.
The external source can be connected to the external supply connector (P21) and the VEXT->nRF switch (SW10) put in 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 nRF5340 SoC that is supplied from this source, it is recommended to supply the VDD domain from a different source to prevent the pins of the SoC to be connected to unpowered devices.
To avoid voltage differences on the PDK, the External supply is also connected to the input of the voltage follower when SW10 is in the ON position. The voltage follower circuit requires 5 V to be present on the PDK, see section 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 PDK should be set in the nRF only mode, see section Operating modes.