nRF52 DK power supply

The nRF52 DK has three power options: USB (5 V), external power supply (1.7 V to 3.6 V), and coin cell battery.

Figure 1. Power supply options (front)

Figure 2. Power supply options (back)

Power supply options on nRF52 DK (back): Coin cell battery

The 5 V from the USB is regulated down to 3.3 V through an onboard voltage regulator. The battery and external power supply are not regulated. The power from the regulator and external supply is routed through diodes for reverse voltage protection (D1 and D7), where the circuit is supplied from the source with the highest voltage. The power from the battery is routed through a load switch and a transistor. These are controlled by the regulator voltage or external voltage, so if any of the two other sources are present, the battery is disconnected from the circuit.

Note: When USB is not powered, the interface MCU is in dormant state and draws an additional current of approximately 20 mA to maintain the reset button functionality. This affects current consumption, but not the nRF52832 current measurements, as described in Current measurement.

Figure 3. Power supply circuitry

The reverse voltage protection diodes for the regulator and external supply 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.

Table 1. Protection diode bypass solder bridges
Power source	Protection bypass	Voltage level
USB	SB10	3.3 V
External supply	SB12	1.7 V to 3.6 V

Figure 4. Protection diode bypass solder bridges

Solder bridges SB10, SB11 and SB12 on the nRF52 DK

Note: Connect only one power source at a time. Shorting the solder bridges removes the reverse voltage protection.