nRF52840 SoC direct supply

nRF52840 DK Hardware

The application System on Chip (SoC) can be powered 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 on 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.

Figure 1. VEXT->nRF switch (SW10)
VEXT->nRF switch (SW10)

Since only the nRF52840 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 on SW10 is in the ON position. The voltage follower circuit requires 5 V supplied to the DK. For more information, 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. For more information, see nRF only mode.

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. For more information, see External memory.