The power for the interface MCU is routed through two load switches, one for the VDD supply and one for the USB supply. This makes it possible to disconnect the interface MCU from the power domain when not in use.
Figure 1. Interface MCU power switch
These switches are controlled by the presence of a USB connected to the interface MCU USB connector (J2), and the state of the nRF only switch (SW6). See Modes of operation for more information.