This device integrates Fast Role Swap which is a great new feature which is defined in the latest USB PD version 3.0 specifications, affects further Type-C interface power design. The charger quickly swaps from power sink role to power source role to provide OTG output voltage to accessories when the original power source is disconnected

Figure 2-2 shows a traditional power solution for FRS. Notebook uses a USB PD controller to detect the FRS signal and notify the host. After FRS event is detected, the buck-boost charger stops operation, and 5 V DCDC converter is enabled with its input from battery pack. It needs a complicated power mux, and only supports a fixed OTG voltage which is set by DCDC output voltage.

Figure 2-3 shows a new solution that the buck-boost charger is able to operate in forward and reverse operation due to its symmetrical architecture. To compare with the traditional power solution (Figure 2-2), the new solution (Figure 2-3) eliminates the DCDC converter and power mux. Most importantly, the new solution provides USB On-the-Go (OTG) full 5 V - 20 V seamlessly after FRS event, while the typical solution cannot.