VDD power sources

The main supply voltage (VDD) is sourced from the 5 V domain, external power supply, and coin cell battery.

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 coin cell battery and external power supply are not regulated.

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

For more information about power sources, see nRF5340 power source.

The power sources are routed through a set of load switches, which are controlled by logic to prioritize the power sources in the correct manner.

If the high voltage regulator of the nRF5340 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 internal transistor body diode powers the VSUPPLY net, which is used to supply the gates that control the enable signal for the power 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