User Manual

nRF51 Development Kit User Guide v1.0
Page 12
5.3 Power supply
The nRF51 DK board has several power options:
Figure 7 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.
Note: When not USB 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 board
current consumption, but will not affect the nRF51 current measurements as described in
Section 5.7 “Measuring current” on page 18.
USB
External
power supply
Coin cell
battery