System and method for enumerating a USB device using low power

A Universal Serial Bus (USB) device, comprising:

• a battery;
• at least one port, coupled to the battery, wherein the at least one port is for coupling to a host USB device, wherein the battery is charged by the host USB device, wherein, during operation, the at least one port receives an enumeration request from the host USB device;
• and
• a USB PHY coupled to the battery, wherein, when the USB device is coupled to the host USB device, the USB PHY detects a charge state of the battery, wherein, when coupled to the host USB device, the USB PHY enables the USB device to engage in USB device enumeration in response to the enumeration request when the charge state of the battery is sufficient to engage in the USB device enumeration;
• wherein the USB PHY comprises first circuitry, wherein the first circuitry engages in first circuitry enumeration of the USB device when the charge state of the battery is not sufficient to engage in the USB device enumeration, wherein the USB PHY uses power received from the host USB device in performing the first circuitry enumeration, and wherein the first circuitry enumeration is distinct from the USB device enumeration;
• and
• wherein the USB device is fully functional with respect to the host USB device when enumerated using the USB device enumeration, and wherein the USB device is not fully functional with respect to the host USB device when enumerated using the first circuitry enumeration.