An apparatus includes a connector, for providing a physical connection to a USB device, a detection circuit, operable to detect attachment of a USB device; and a charging circuit, for charging a battery of a portable device using current drawn from a USB device, the charging circuit being operable, if it is detected that a USB device is attached, to generate a start-up request signal. The apparatus has a charging mode in which power is provided by the charging circuit to the battery, and a USB connection mode for providing a USB connection. The apparatus also includes a control unit, operable in response to the start-up request signal to determine whether power supplied by the battery meets a predetermined criterion. The control unit is also operable, if it is determined that the predetermined criterion is not met, to control the apparatus to be in the charging mode and prevent the apparatus from entering the USB connection mode and operable, if it is determined that predetermined criterion is met, to control the apparatus to enter the USB connection mode.