The USB-C pinout allows it to consolidate data, power, and video signals into a single, universal port.
For over two decades, USB has unified device peripherals. With USB-C, that role expands even further. Now the EU’s charging standard, the USB-C, is more than a reversible plug; it delivers high-speed data, substantial power, and video.
For PCB designers, understanding the USB-C connector pinout is essential. Though complex, mastering its layout and operating modes is crucial for modern electronics. This guide summarizes the USB-C pinout, its modes, and key design considerations.
The Basics of the USB-C Connector Pinout
A critical distinction to make is that “USB-C” refers to the physical connector, not the data transfer protocol (like USB 2.0, USB 3.2, or USB4). The connector’s 24-pin, symmetrical design enables its key features, including reversible mating and a multitude of operating modes.
The receptacle (the port on the device) contains all 24 pins, allowing for the orientation to be flipped. The plug (on the cable), however, is slightly different: it only contains one set of USB 2.0 D+/D- pins (A6/A7), and the B6/B7 pin locations are absent. Additionally, on the plug, the B5 pin is repurposed as VCONN, which is used to power electronics inside active or electronically marked cables.
| USB-C 24 Pins Layout | ||||||||||||
| Pin Des | A1 | A2 | A3 | A4 | A5 | A6 | A7 | A8 | A9 | A10 | A11 | A12 |
| Pin Name | GND | TX1+ | TX1- | VBUS | CC1 | D1+ | D1- | SBU1 | VBUS | RX2- | RX2+ | GND |
| GND | RX1+ | RX1- | VBUS | SBU2 | D2- | D2+ | CC2 | VBUS | TX2- | TX2+ | GND | |
| Pin Des | B12 | B11 | B10 | B9 | B8 | B7 | B6 | B5 | B4 | B3 | B2 | B1 |
The USB Type-C receptacle pinout viewed from the end. The plug pin designators are mirrored horizontally across the center pins alongside slight changes to the pinout.7777
| USB-C Connector Pinout Description | ||
| Pin(s) | Function | Description |
| GND | Ground | Return plane for the connection. |
| VBUS | Power | Main power supply for the device. |
| TX1+/TX1-, TX2+/TX2- | High-speed differential pairs (Transmit) | Positive and negative lines used for high-speed protocols such as USB 3.x, USB4, DisplayPort, and Thunderbolt. |
| RX1+/RX1-, RX2+/RX2- | High-speed differential pairs (Receive) | Positive and negative lines for high-speed data reception. |
| D1+/D1-, D2+/D2- | USB 2.0 differential pairs | Legacy USB 2.0 communication; only one pair is active depending on plug orientation. |
| CC1/CC2 | Configuration Channel | Detects connection, orientation, cable type, and negotiates power delivery and alternate modes. One CC pin can also serve as VCONN to power active cables. |
| SBU1/SBU2 | Sideband Use | Auxiliary pins for alternate modes, such as the AUX channel in DisplayPort. |
Alternatively, the plug for USB-C pinout substitutes the channel config pin on B5 with a VCONN pin to enable power delivery services. The B6 and B7 pins are also removed, and the second USB 2.0 differential data lines go unreplaced.
One of the most compelling features of USB-C is the number of operating modes available. Since it has more pin counts and functionality than older physical USB systems, it can cover deprecated protocols without needing an intermediate translation. While this allows users to interface with older devices and systems, USB-C offers much more than compatibility with legacy standards. The gains in transfer speeds enable the support of newer, modern protocols for audiovisual purposes with a single connector system.
USB Operating Modes, Applications, and Pin Configurations
The true power of the USB-C connector lies in its ability to support multiple modes by re-purposing its pins. The following guide details common USB-C operating modes, including USB 2.0, High-Speed Data (USB 3.x/USB4), USB Power Delivery (PD), and Alternate Modes with their corresponding active pin configurations, providing a clear reference for design implementation.
How USB-C Modes are Negotiated
The intelligence of USB-C lies in the Configuration Channel (CC) pins. When a connection is made, a dedicated controller IC uses the CC line to perform a digital “handshake” that determines how the port will operate.
This negotiation process establishes several key things:
- Detection & Orientation: Pull-up/pull-down resistors on the CC line detect the connection and the plug’s orientation, allowing the system to correctly route the USB 2.0 (D+/D-) signals.
- Power Contract: The source (charger) advertises its power capabilities (e.g., “I can provide 5V/3A and 9V/2A”). The sink (device) requests one of these profiles. Once agreed, the source provides the requested voltage on VBUS. This is the core of USB Power Delivery (PD).
- Alternate Mode Entry: If a device supports a feature like DisplayPort, it advertises this capability over the CC line. If the partner device also supports it, they agree to enter that “Alternate Mode,” and internal high-speed switches reroute the TX/RX pins to carry video data instead of USB data.
This negotiation all happens automatically in milliseconds upon connection, allowing the single port to adapt to the specific needs of the connected devices.
Mode 1: USB 2.0 (Legacy Data and Basic Power)
This is the most basic operational mode of a USB-C connector, designed for backward compatibility and low-speed applications. It relies only on the D+/D- differential pair (A6/A7 or B6/B7) for data, along with the VBUS and GND pins for power.
- Common Applications: Keyboards, mice, basic audio interfaces, firmware update ports, and charging low-power devices, such as wireless headphones.
- Key Feature: The simplicity of this mode allows for longer and less expensive cable designs, with reliable connections possible up to 4 meters.
- Design Considerations: The D+/D- lines should still be routed as a 90Ω differential pair to ensure good signal integrity. It is critical to always use certified, compliant cables and adapters, as non-compliant versions with incorrect pull-up resistors (Rp) can cause a device to draw excessive current, risking damage to the host.
| Active Pins in USB 2.0 Mode | ||||||||||||
| Pin Des | A1 | A2 | A3 | A4 | A5 | A6* | A7* | A8 | A9 | A10 | A11 | A12 |
| Pin Name | GND | VBUS | D1+ | D1- | VBUS | GND | ||||||
| GND | VBUS | VBUS | GND | |||||||||
| Pin Des | B12 | B11 | B10 | B9 | B8 | B7* | B6* | B5 | B4 | B3 | B2 | B1 |
*Only one USB 2.0 differential pair can be active at any one time in this mode. Because of the reversibility of USB-C, B6/7 could be utilized instead of A6/7.
Mode 2: High-Speed Data (USB 3.x / USB4)
To achieve the fast data transfer rates modern devices demand, the USB-C connector utilizes its four high-speed TX/RX differential pairs. This mode is essential for any device where data throughput is critical, such as external SSDs, high-resolution 4K webcams, VR headsets, and powerful docking stations.
When designing for high-speed data, signal integrity is paramount.
- Controlled Impedance: The high-speed TX/RX pairs must be routed as controlled-impedance differential pairs, typically 90Ω, along their entire length.
- Length Matching: The two traces within each pair must be precisely length-matched to prevent timing skew, which can corrupt data.
- Minimize Discontinuities: Avoid using vias on these traces whenever possible. If a via is unavoidable, it must be carefully designed with adjacent ground stitching vias to maintain a continuous return path and minimize impedance changes.
If a high-speed device only connects at slow USB 2.0 speeds or experiences intermittent disconnects, a signal integrity issue in the high-speed routing is very often the root cause.
| Active Pins in High-Speed Mode | ||||||||||||
| Pin Des | A1 | A2* | A3* | A4 | A5* | A6† | A7† | A8 | A9 | A10* | A11* | A12 |
| Pin Name | GND | TX1+ | TX1- | VBUS | CC1 | VBUS | GND | |||||
| GND | RX1+ | RX1- | VBUS | VBUS | GND | |||||||
| Pin Des | B12 | B11* | B10* | B9 | B8 | B7† | B6† | B5* | B4 | B3* | B2* | B1 |
*: For single-lane mode, only the differential pairs closest to the active channel config pin will be in use. Double-lane mode utilizes channel config pins and the four Tx/Rx differential pairs.
†: The USB 2.0 differential pairs generally go unused in USB 3.x mode, but certain devices can operate simultaneously or use the USB 2.0 differential pairs as backup lines in case of a USB 3.x transmission failure.
Mode 3: USB Power Delivery (PD)
Power delivery can provide power far above most USB standards: 20V/5A with specialty cables (or 20V/3A as the default specification). The Power Delivery mode is compatible with any data protocol, provided one of the two CC pins is available, allowing for simultaneous power and data transfer.
Because of the high power capability, the most common design pitfall is underestimating the current on the VBUS line. The VBUS and GND traces on your PCB must be made wide enough to handle the maximum negotiated current (e.g., 3A or 5A) without a significant voltage drop or overheating. Always use a PCB trace width calculator when routing these nets. Implementing USB PD also requires a dedicated PD controller IC.
| Active Pins in Power Delivery Mode | ||||||||||||
| Pin Des | A1 | A2 | A3 | A4 | A5* | A6 | A7 | A8 | A9 | A10 | A11 | A12 |
| Pin Name | GND | VBUS | CC1 | VBUS | GND | |||||||
| GND | VBUS | VBUS | GND | |||||||||
| Pin Des | B12 | B11 | B10 | B9 | B8 | B7 | B6 | B5* | B4 | B3 | B2 | B1 |
*Only one of the channel config pins is utilized in Power Delivery mode, but once again, the reversibility of the USB-C system requires either A5 or B5 (but not both) during operation.
Additional Functionality and Support for USB-C Connectors
Beyond standard USB data and power, the USB-C specification includes several special modes that reconfigure the pinout for other functions. These modes enable the single connector to support video, analog audio, and even hardware debugging, further enhancing its versatility and helping to eliminate the need for other legacy ports.
Alternate Mode
Perhaps the most valuable feature for modern device design is “Alternate Mode.” This allows the USB-C connector to carry non-USB protocols by re-purposing the high-speed TX/RX data pairs. For PCB designers, this capability is a powerful tool for reducing the number of physical ports on a device, saving board space, and simplifying routing in high-density designs.
Supported interfaces include:
- DisplayPort: A packetized digital interface for high-resolution video and audio. This is the most common alternate mode, enabling direct connection to monitors.
- Thunderbolt™: A high-speed protocol developed by Intel and Apple that combines PCIe and DisplayPort data into a single stream, offering extremely high bandwidth for demanding peripherals. The latest versions use the USB-C connector exclusively.
- HDMI: Through the use of an adapter, the connector can be configured to output HDMI video and audio signals.
- MHL (Mobile High-Definition Link): An older standard used for connecting mobile devices to displays.
| Active Pins in Alternate Mode | ||||||||||||
| Pin Des | A1 | A2 | A3 | A4 | A5* | A6* | A7* | A8 | A9 | A10 | A11 | A12 |
| Pin Name | GND | TX1+ | TX1- | VBUS | CC1 | D1+ | D1- | SBU1 | VBUS | RX2- | RX2+ | GND |
| GND | RX1+ | RX1- | VBUS | SBU2 | VBUS | TX2- | TX2+ | GND | ||||
| Pin Des | B12 | B11 | B10 | B9 | B8 | B7* | B6* | B5* | B4 | B3 | B2 | B1 |
*Alternate mode allows for USB 2.0 differential pair transfer. Similar to USB 2.0, only one pair can be active at a time.
Audio Adapter
USB-C can support audio output from an on-device ADC or one within the adapter. Similar to other modes, device charging is allowed while using Audio Adapter Mode, but only at USB 2.0 levels (5V/500mA) as the channel config pins are in use.
| USB-C Audio Adapter Mode Pinout | ||||||||||||
| Pin Des | A1 | A2 | A3 | A4 | A5* | A6* | A7* | A8* | A9 | A10 | A11 | A12 |
| Pin Name | GND | VBUS | CC1 | R | L | MIC | VBUS | GND | ||||
| GND | VBUS | AGND | CC2 | VBUS | GND | |||||||
| Pin Des | B12 | B11 | B10 | B9 | B8* | B7* | B6* | B5* | B4 | B3 | B2 | B1 |
*Audio Adapter mode places the audio channel on one of the two USB 2.0 differential pairs, dependent on the orientation of the receptacle.
Debug
For hardware engineers and accessory developers, the USB-C specification defines a special Debug Accessory Mode. This mode allows engineers to test the functionality of a USB-C port and its connection to a device. A typical use case is to isolate hardware faults; for example, if a DisplayPort connection fails, a designer can use this mode to directly probe the TX/RX pairs with an oscilloscope to verify signal integrity. It is entered by using a special test fixture that pulls the CC pins high or low in a specific way. Once in this mode, all digital logic is disconnected from the high-speed and sideband pins, allowing them to be used for direct signal analysis. When Power Delivery is active, all 14 signal lines (the four TX/RX pairs, two D+/D- pairs, and two SBU lines) can be used for debugging.
| Active Pins in Debug Mode | ||||||||||||
| Pin Des | A1 | A2* | A3* | A4* | A5 | A6* | A7* | A8 | A9 | A10* | A11* | A12 |
| Pin Name | GND | TX1+ | TX1- | VBUS | CC1 | D1+ | D1- | SBU1 | VBUS | RX2- | RX2+ | GND |
| GND | RX1+ | RX1- | VBUS | SBU2 | D2- | D2+ | CC2 | VBUS | TX2- | TX2+ | GND | |
| Pin Des | B12 | B11* | B10* | B9 | B8* | B7* | B6* | B5 | B4 | B3* | B2* | B1 |
The key to unlocking the potential of the most recent USB connector system lies in understanding the USB-C connector pinout and the features each mode can support. As much as end users enjoy the flexibility of an all-inclusive connector, designers benefit even more from a streamlined approach in compact layouts. Given the importance of the connector to a wealth of device applications, ensuring the quality of its associated land pattern can be the difference between a PCB assembly and testing progressing smoothly or requiring rework or revision.
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