How do I control the VBUS on my USB-C downstream facing or dual-role port?
The USB-C specification defines 3 types of ports that a type-C connector can be configured as. These are downstream facing (DFP), upstream facing (UFP), and dual-role (DRP). A dual role port can act as both a DFP or a UFP depending on the attached device.
When making a DFP or DRP, you need to control the Type-C VBUS such that VBUS is only supplied when a UFP is attached to the type-C port and the CC negotiation has finished. In our CC controllers (TUSB320/321/322), this is done using the ID pin. The ID pin will remain high when there is no attachment, or when the type-C port is acting as a UFP. ID will go low only when a UFP is attached to the port, negotiation is complete, and our DFP/DRP expects to provide VBUS.
Here is an example diagram showing the behavior of the ID pin:
If you are using a VBUS switch with a low-enable pin, the ID pin can be directly routed to the enable on your switch. Here is a diagram showing how the CC controller and VBUS switch could fit into a Type-C ecosystem:
A UFP does not require a VBUS switch as it never supplies VBUS itself.
