The main supply (VDD) can be 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 is controlled by logic to prioritize the power sources in the correct manner.
If the high voltage regulator of the nRF5340 is used, the Preview Development Kit (PDK) will be supplied from the VDD_nRF voltage follower regardless of the state of the other power sources.
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.
| Power source | Power switch bypass | Voltage level |
|---|---|---|
| Regulator | SB34 | 3.0 V |
| Coin cell battery | SB35 | Battery |
| External supply | SB36 | 1.7 V–3.6 V |
