Hardware description
Figure 6: 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 board current consumption, but not the nRF52832 current measurements, as described in
Measuring current
on page 21.
Figure 7: 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.
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