Figure 1. Since USB Type-C hub ports will soon be able to deliver up to 100 W of bidirectional power, the door is open for many scenarios, such as displays powering or being powered by a network of devices.
To achieve 100 W, USB Power Delivery is used. This is an optional feature that works with unmodified USB Type-C cables and connectors, so any Type-C connector or cable that draws power from VBUS must be capable of delivering 100 W (@ 5 A).
After establishing voltage limits, the USB Type-C hub current specification provides two key extensions: it can provide higher current (5 A @ 5 V, vs 3.1 or 1.0 A @ 5 V), and it allows power management of the current it provides .
Therefore, the downstream port (DFP) advertises the amount of current it can provide to the upstream port (UFP) using the two channel configuration (CC) pins discussed earlier. When implementing USB PD, the USB PD Biphase Marker Coding (BMC) signal on the CC line is used to communicate between USB Type-C hub ports, but this can only begin after VBUS is stable.
USB PD Binary Frequency Shift Keying (BFSK) on VBUS can also be used to communicate with USB PD products, but only if the USB PD BMC is unable to establish PD communication. If a USB Type-C hub-based UFP supporting USB PD BFSK requires more than 1.5 A, VCONN needs to be provided and confirmation that the cable is electronically marked and capable of meeting the requested current level.
Now is the time to note that while all USB Type-C based devices are required to support USB Type-C Current, support for other USB-defined power methods is optional. These other alternative methods include USB Power Delivery, USB BC 1.2, and the default power mode for USB 3.1 and USB 2.0.
If all power modes are available, there is an order of precedence, as shown in Figure 2. USB BC 1.2 replaces USB 2.0 and USB 3.1, USB Type-C current of 1.5 A and 3.0 A replaces USB BC 1.2, USB Power Delivery replaces USB Type-C current.
Figure 2. USB Power Delivery has a number of profiles ranging from 10 W to 100 W and takes precedence over all other power modes if present.
