nRF52840 DK v1.0.0

nRF52840 direct supply

It is possible to power the System on Chip (SoC) directly from a source without powering the rest of the board 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.

Figure 1. VEXT->nRF switch (SW10)
VEXT->nRF switch (SW10) on nRF52840 DK board

Since it is only the nRF52840 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 board, 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 board, 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 board should be set in the nRF only mode, see section Operating modes.

Note: To reduce trace length and parasitic components, the external memory is connected to the SoC directly instead of using analog switches. It is recommended to cut solder bridges to avoid leakage, see section External memory.