There are different port specifications for current draw via the USB interface. In addition to the specified Standard Downstream Port( SDP), there is the Charging Downstream Port (CDP), which is characterized by a high current draw compared to the SDP port.
The Charging Downstream Port (CDP) is a USB interface for desktops, laptops and other hardware. Currents of up to 1.5 A can be drawn through this interface for powering devices and charging batteries, USB Battery Charging( USB-BC). A device plugged into the USB port detects whether the port is designed for the high current draw by handshaking over the two data lines D+ and D-.