Universal Serial Bus specifications provide critical physical and electrical requirements to electronics manufacturers of USB capable equipment. Adherence to these specifications during product development coupled with standardized compliance testing assures very high degrees of interoperability amongst USB products in the market. Since its inception in the mid 1990s, USB has undergone a number of revisions to enhance utility and extend functionality. For the most up to date standards, please consult the USB Implementers Forum (USB-IF).

All USB ports are capable of providing a 5-V output making them a convenient power source for operating and charging portable devices. USB specification documents outline specific power requirements to ensure interoperability. In general, a USB 2.0 port host port is required to provide up to 500 mA; a USB 3.0 or USB 3.1 port is required to provide up to 900 mA; ports adhering to the USB Battery Charging 1.2 Specification provide up to 1500 mA; and newer Type-C ports can provide up to 3000 mA. Though USB standards governing power requirements exist, some manufacturers of popular portable devices created their own proprietary mechanisms to extend allowed available current beyond the 1500 mA maximum per BC 1.2. While not officially part of the standards maintained by the USB-IF, these proprietary mechanisms are recognized and implemented by manufacturers of USB charging ports.

The TPS2584x-Q1 device supports the most-common USB-charging schemes BC1.2 in popular hand-held media and cellular devices.

The BC1.2 specification includes three different port types:

• Standard downstream port (SDP, supported)
• Charging downstream port (CDP, supported)
• Dedicated charging port (DCP, NOT supported)

BC1.2 defines a charging port as a downstream-facing USB port that provides power for charging portable equipment. Under this definition, CDP and DCP are defined as charging ports.

Table 10-5 lists the difference between these port types.