The Smart Remote 3 DK add-on gets its power from two AA batteries or from the nRF5x Development Kit (DK).
Either alkaline (2 × 1.5 V) or rechargeable NiMH (2 × 1.2 V) batteries can be used. The battery circuit has a protection diode to avoid reverse current if the USB is connected to the nRF5x DK while batteries are inserted.
Smart Remote 3 has a switch for turning the power on or off for most of the circuits. One transistor is used for this, which is controlled by the nRF chip on the nRF5x DK. See Power on/off switch. The low-power accelerometer is always powered.
The voltage from the batteries or nRF5x DK is used unregulated for most part of the design. However, the trackpad requires a stable voltage of 3.3 V. To achieve this, the trackpad gets the power from a fixed step-up/step-down charge pump generator that outputs 3.3 V. See Voltage regulator for the trackpad.
