A separable multi-interface I/O card device comprises an I/O bridge and an I/O device. The I/O bridge includes a host interface for coupling to an electronic device, a bridge unit, and a first I/O bus, wherein the bridge unit is adapted to either convert signals from the host interface into signals of the first I/O bus or convert signals from the first I/O bus into signals of the host interface, and supply power from a power pin of the host interface to the first I/O bus. The I/O device includes an I/O functional unit and a second I/O bus mated with and separably coupled to the first I/O bus so as to send power, I/O, data, and control signals from the host interface to the I/O functional unit.