6.7.1 Battery Charger Detection

The IS2083BM USB transceiver includes built-in battery charger detection that is compatible with the following:

USB BC 1.2 Standard Downstream Port (SDP): This is the same port defined by the USB 2.0 spec and is the typical form found in desktop and laptop computers. The maximum load current is 2.5 mA when suspended, 100mA when connected and not suspended, and 500 mA (max) when connected and configured for higher power.

USB BC 1.2 Dedicated Charger Port (DCP): BC 1.2 describes power sources like wall warts and auto adapters that do not enumerate so that charging can occur with no digital communication at all. DCPs can supply up to 1.5A and are identified by a short between D+ to D-. This port does not support any data transfer, but is capable of supplying charge current beyond 1.5A.

Any device (such as the IS2083BM) that connects to any USB receptacle and uses that power to run itself or charge a battery, must know how much current is appropriate to draw. Attempting to draw 1A from a source capable of supplying only 500mA would not be good. An overloaded USB port will likely shut down or blow a fuse. Even with resettable protection, it will often not restart until the device is unplugged and reconnected. In ports with less rigorous protection, an overloaded port can cause the entire system to Reset. Once the USB transceiver determines the battery charger profile and port type (SDP, CDP, DCP), it interrupts the CPU, which then reads the battery charger profile and port type information out of the USB registers. It uses this information to program the PMU (via the 3-wire PMU interface) with the configuration corresponding to the battery charger profile and port type.