VDD power sources

The main supply (VDD) can be sourced from the 5 V domain and external power supply.

For the 5 V domain, there are two regulators: one fixed 3 V buck regulator and one voltage follower regulator that follows the VDD_nRF voltage. The external power supply is not regulated.

• 5 V domain:
  • Fixed 3 V buck regulator
  • VDD_nRF voltage follower
• External power supply

For more information about power sources, see nRF21540 and nRF52840 power source.

The power sources are routed through a set of load switches, which is controlled by logic to give the correct priority of the power sources.

If the high voltage regulator of the nRF52840 System on Chip (SoC) is used, the Development Kit (DK) is supplied from the VDD_nRF voltage follower regardless of the state of the other power sources.

Figure 1. Power supply circuitry

The power switches work in the way that the body diode of the internal transistor powers the VSUPPLY net, which supplies the gates controlling the enable signal of the switches. If 5 V is present, the switches for external supply and battery are disabled. If external supply is present, the switch for the battery is disabled.

The power switches can be bypassed by shorting one or more solder bridges.

Figure 2. Power switch bypass solder bridges