The nRF52 PDK has three power options: 5 V from the USB, external power supply, and coin cell battery.
Figure 1. Power supply options
The 5 V from the USB is regulated down to 3.3 V through an on-board voltage regulator. The battery and external power supply are not regulated. The power sources are routed through a set of diodes (D1A, D1B, and D1C) for reverse voltage protection, where the circuit is supplied from the source with the highest voltage.
Important: When USB is not powered, the Interface MCU is in dormant state and will
draw an additional current of ~ 20 μA in order to maintain the reset button functionality. This
will affect current consumption, but not the nRF52832 current measurements, as
described in Measuring current.
Figure 2. Power supply circuitry
The reverse voltage protection diodes will add a voltage drop to the supply voltage of the circuit. To avoid this voltage drop, the diodes can be bypassed by shorting one or more solder bridges.
| Power source | Protection bypass | Voltage level |
|---|---|---|
| USB | SB10 | 3.3 V |
| Coin-cell battery | SB11 | Battery |
| External supply | SB12 | 1.7 V - 3.6 V |
Figure 3. Protection diode bypass solder bridges
Important: Connect only one power source at the time. Shorting the solder bridges
removes the reverse voltage protection.