Final answer:
USB 3.0 devices requiring more than 150 mA of power must be self-powered, having their own power supply separate from the USB connection.
Step-by-step explanation:
USB 3.0 devices that need more than 150 milliamperes (mA) of power are considered self-powered. This is because USB 3.0 ports supply a maximum of 150 mA of power in a low-power state and can provide up to 900 mA when in a high-power state. For a device that requires more power than this, it must be self-powered, meaning it must have its own power supply, separate from the USB connection to the host computer. It's also important to consider the efficiency of the device, as the actual current necessary could be greater than what is nominal due to factors like power conversion efficiency.