SLVAFG6A December 2022 – November 2023 TPS25762-Q1 , TPS25772-Q1
Hybrid Mode is an optional power policy that behaves as a hybrid of the Assured Capacity Policy and Shared Capacity Policy. It provides the benefit of the Assured Capacity Policy by initially advertising the Port Max Power when one Sink is connected, while allowing equal distribution of the Total USB VBUS Power, similar to the Shared Capacity Policy, when two Sinks are connected.
There are some Sink devices that request power based on the first Source Capabilities received and do not attempt to renegotiate for a more favorable contract when higher PDOs are offered in following Source Capabilities messages. This is a problem when FSP is desired, so Source ports are configured as Shared Capacity and Port Min Power is advertised in the initial Source Capabilities message. With Hybrid Mode, FSP is possible while ensuring that the aforementioned Sink-type's power requirements are met.
Hybrid Mode can be enabled from either the Simple Configuration or Advanced Configuration view. After the SPM Engine parameters are entered with Assured Capacity Policy selected, Hybrid Mode can be enabled by modifying the Total USB VBUS Power (System Max Power) to a value less than the sum of Port A and Port B's Max Power. The GUI then displays Hybrid Mode in red text to indicate that Hybrid Mode is active as shown in Figure 3-9 and Figure 3-10.
The Hybrid Mode parameters shown in Table 3-5 are used in the power distribution method.
Hybrid Mode Parameters | Description |
---|---|
Equally Divided System Power | Equally divided Total USB VBUS Power distributed to each port
when two PD-Sinks are connected: Total USB VBUS Power / Total number of ports. |
Single Port Max Power Capacity | Maximum VBUS power for a port when a single PD-Sink is connected:
Total USB VBUS Power - Port Min Power (limited up to the Port Max Power) |
Non-PD USB-C Power | USB Type-C 5 V output for non-PD based USB Type-C charging; 7.5W or 15W. |
The typical flow of the Hybrid Mode power distribution is as follows:
In the event where one PD Sink and one non-PD Sink are connected to the ports, the Equally Divided System Power is initially distributed to each Sink. This connection takes roughly 8.5 seconds for the TPS257xx-Q1 firmware to identify a non-PD Sink. Once a non-PD Sink is identified, the SPM Engine can reallocate and redistribute system power; Non-PD USB-C Power is distributed to the non-PD Sink and the remaining power (the difference between the Total USB VBUS Power and the Non-PD USB-C Power) is distributed to the PD Sink. The Non-PD USB-C Power can be selected by configuring the USB Type-C Current parameter from the GUI's USB PORT(S) window (see Figure 3-11).
See Section 5.3 for example scenarios of Hybrid Mode to better understand this mode's power distribution method.