Type-C™ CC and VCONN Signals
Upstream Facing Port (UFPs) and Downstream Facing Port (DFPs) each have a CC1 and a CC2 pin. These pins connect to the CC and VCONN lines of the Type-C™ cable. Both CC1 and CC2 must be able to support both the CC and the VCONN functions.
CC1 and CC2
Resistors are attached to these signals in various configurations depending upon the usage. Pull-up and Pull-down resistors are used on UFP and DFP elements, as well as within electronically marked active cables (see Type-C Cable page for details)
The attached resistors allow the CC pins to perform the following functions:
- Detection of cable attachment
- Detect the orientation of the attached cable
- Advertisement of the power capabilities of the DFP
Upstream Facing Ports (UFPs) are connected with the pull-down resistor (Rd) on CC1 and CC2. Type-C cables are populated with only one CC line. By monitoring both CC1 and CC2, the Downstream Facing Port (DFP) can determine if a cable is connected and the orientation of the cable.
Powered Type-C cables, both electronically marked and managed active cables, have pull-down resistors (Ra) connected to the non-CC line. Monitoring Ra allows the DFP to recognize the existence and orientation of a powered Type-C cable.
Cable Connection State
| CC1 | CC2 | Status | Orientation |
|---|---|---|---|
| — | — | Nothing connected | n/a |
| Rd | — | UFP connected | Normal |
| — | Rd | UFP connected | Flipped |
| — | Ra | Power Cable, no UFP connection | Normal |
| Ra | — | Power Cable, no UFP connection | Flipped |
| Rd | Ra | Power Cable with UFP connection | Normal |
| Ra | Rd | Power Cable with UFP connection | Flipped |
How Much Power Can the DFP Supply?
The value of the pull-up resistors (Rp) attached to CC1 and CC2 advertise the current supplying capabilities of the DFP. Rp can be tied to a 3.3 V, 5V, or current source signal. The following table shows the values of Rp used to advertise current:
USB Type-C™ CC and VCONN Signals
| DFP Capability | Rd for 5 V signal | Rd for 3.3 V | Current source |
|---|---|---|---|
| USB 2.0 Default 500 mA | 56 kΩ | 36 kΩ | 80 μA |
| USB 3.x Default 900 mA | 56 kΩ | 36 kΩ | 80 μA |
| 1.5 A @ 5V | 22 kΩ | 12 kΩ | 180 μA |
| 3.0 A @ 5V | 10 kΩ | 4.7 kΩ | 330 μA |
VCONN
VCONN is a 5V 1W power supply used to power the Integrated Circuit (IC) within an electronically marked Type-C cable. The DFP will supply the VCONN power upon start-up.
If two Dual Role ports are connected, and they both support the Power Delivery Protocol, the responsibility for supplying VCONN can be passed to the UFP with negotiation. See the Power Delivery Protocol page for implementation details.
VCONN can be supplied in one of two ways:
- If a valid Rp/Rd connection is detected on one of the CC pins, VCONN can be connected to the other pin.
- After a valid Rp/Rd connection is detected on one CC pin, the other pin is monitored for a valid Ra before connecting VCONN.