SLVAFG6A December 2022 – November 2023 TPS25762-Q1 , TPS25772-Q1
The Shared Capacity Policy is where the sum of the Port Max Power, as designed, is less than the Total USB VBUS Power. When the Source ports are configured in Shared Capacity, Port Min Power is guaranteed for each port while the remaining power stored in Power Reserve is shared between Port A and Port B.
An example of the Shared Capacity Policy is shown in Figure 3-6 where the Total USB VBUS Power is 75 W, Port A and B's Min Power are both 15 W, and there is 45 W in Power Reserve. Port A connects to a Sink that requests 45 W. Port A's Min Power of 15 W is guaranteed, so 30 W is distributed from Power Reserve to deliver a total of 45 W, the Sink's requested power. The remaining power in Power Reserve is now 15 W, so with Port B's Min Power of 15 W, a total of 30 W is available for Port B. From this point, what occurs when a second Sink connects to Port B is dependent on the Port Partner's Sink Capabilities and is discussed in the following subsections.
Figure 3-7 and Figure 3-8 show the Shared Capacity Policy selection in the GUI's Simple Configuration view and Advanced Configuration view.
Note that although freely configurable in the GUI, according to the USB Type-C Cable and Connector Specification Release 2.2, the following behavioral rules must apply for Source ports configured with Shared Capacity Policy: