USB-C Wiring Diagram: 24-Pin Connector Pinout, CC Lines, and Power Delivery Explained

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A USB-C wiring diagram maps all 24 pins of the reversible USB Type-C connector, covering VBUS, GND, SuperSpeed TX/RX pairs, CC1/CC2 for orientation and PD negotiation, SBU sideband, and D+/D− legacy data.

The USB Type-C connector is defined by the USB Type-C Cable and Connector Specification, maintained by the USB Implementers Forum (USB-IF). Its 24 pins occupy a symmetrical, reversible connector body — the plug can be inserted in either orientation and the electrical system detects the orientation automatically using the CC (Configuration Channel) pins.

The 24 pins break down into functional groups:

VBUS (pins A4, A9, B4, B9): Four VBUS pins carry the power bus voltage — 5 V by default, negotiated up to 48 V under USB Power Delivery 3.1 (PD 3.1). Multiple pins are used to distribute current and reduce contact resistance.

GND (pins A1, A12, B1, B12): Four ground return pins, again distributed for current sharing.

CC1 and CC2 (pins A5 and B5): The Configuration Channel pins are the intelligence of USB-C. When a cable is inserted, CC1 and CC2 determine plug orientation (one CC pin connects to the cable CC wire; the other to the VCONN pin supplying active cable electronics). In power delivery, CC1 and CC2 carry the BMC-encoded PD negotiation protocol between power source and sink — allowing the sink to request a specific voltage and current up to 48 V / 5 A (240 W) under PD 3.1 EPR (Extended Power Range).

SuperSpeed differential pairs (TX1+/−, TX2+/−, RX1+/−, RX2+/−): Eight pins carry USB 3.x SuperSpeed data at up to 20 Gbps per lane (USB 3.2 Gen 2×2) or higher with USB4 at up to 40 Gbps. The two TX and two RX pairs allow simultaneous bidirectional data at full throughput.

D+ and D− (pins A6, A7 / B6, B7): USB 2.0 legacy data differential pair, present for backward compatibility with USB 2.0 devices.

SBU1 and SBU2 (pins A8, B8): Sideband Use pins. These are reserved for alternate mode use — for example, DisplayPort Alt Mode uses SBU1 and SBU2 for audio return channel (ARC) and other DisplayPort auxiliary signals.

VCONN (on CC2 or CC1, depending on orientation): Powers active electronics in electronically marked cables (E-Marker chips), which identify cable capabilities (current rating, USB4 certification, etc.) to both ends of the connection.

All wiring references are illustrative. USB-C connector assembly requires precision tooling and controlled impedance PCB design — it is not a field-terminated connector.

How to wire usb c wiring diagram

Identify the USB-C connector standard and required functionality Determine what the connection needs to carry: charging only (VBUS/GND/CC minimum), USB 2.0 data, USB 3.x SuperSpeed data, Power Delivery, DisplayPort Alt Mode, Thunderbolt, or USB4. Each capability requires a different set of conductors to be implemented. A charging-only cable needs far fewer conductors than a Thunderbolt 4 cable.
Understand the pin assignment before any hardware work Obtain the USB Type-C Specification pinout (available from USB-IF). The 24 pins are split across two rows (A-side and B-side), with the A-side and B-side mirroring each other to allow reversible insertion. Pin A1/B1 = GND, A4/B4 = VBUS, A5 = CC1, B5 = CC2, A6/B6 = D+, A7/B7 = D−, A8/B8 = SBU1/SBU2, and A2/A3/B2/B3 and A10/A11/B10/B11 are the SuperSpeed TX and RX differential pairs.
For power delivery integration, understand the CC resistor scheme Without active PD negotiation, a power source signals its current capability to a sink via pull-up resistors on CC1/CC2 (Ra and Rp values). A source capable of 5 V/900 mA uses Rp = 56 kΩ; 5 V/1.5 A uses Rp = 22 kΩ; 5 V/3 A uses Rp = 10 kΩ. A powered sink pulls CC down with Rd = 5.1 kΩ. The combination of pull-up and pull-down determines the advertised current level. Active PD negotiation uses the CC wire to exchange packets at 300 kbps BMC encoding.
For cable assembly or PCB design, match impedance requirements USB 3.x SuperSpeed differential pairs require a controlled characteristic impedance of 90 Ω ± 15% differential within the cable. USB4 and Thunderbolt tighten this to ±10%. PCB routing from the USB-C connector pads to the controller IC must also maintain controlled impedance and minimise length asymmetry within each differential pair (skew control). This is not achievable without impedance-controlled PCB stack-up and appropriate EDA tools.
Verify VCONN provision for active cable support If the design must support E-Marker cables or active USB-C cables (optical or active copper), the host/DFP (Downstream Facing Port) must supply VCONN — typically 5 V at 70–700 mW — on the CC pin that is not used for CC communication (determined after orientation detection). Include a VCONN power switch with current limiting in the host design. UFP (Upstream Facing Port) devices such as chargers do not supply VCONN.
Test the connection with a USB-C cable tester before deployment USB-C cable testers (commercially available, dedicated devices) verify which conductors are present and connected, confirm correct CC resistor values, and identify miswired cables. Testing is essential because a cable that is only missing the SuperSpeed conductors will still charge and pass USB 2.0 data, making a wiring error non-obvious in casual use but problematic for high-speed or Alt Mode operation.

Specifications

USB-C connector pin count	24 pins (12 on A-side, 12 on B-side; symmetrical for reversible insertion)
VBUS voltage range	5 V (default) up to 48 V under USB PD 3.1 EPR
Maximum power (USB PD 3.1 EPR)	240 W (48 V × 5 A); requires EPR-rated E-Marker cable and EPR-capable source and sink
CC line communication speed (PD protocol)	300 kbps (BMC-encoded biphase mark coding)
SuperSpeed differential pair impedance	90 Ω ± 15% differential (USB 3.x); ± 10% for USB4/Thunderbolt
USB 3.2 Gen 2×2 maximum data rate	20 Gbps aggregate (2 × 10 Gbps using both TX and RX SuperSpeed lane pairs)
USB4 maximum data rate	40 Gbps (USB4 Gen 3×2) or 80 Gbps (USB4 Gen 4, requires USB4 v2.0 capable devices)
VCONN supply limit	5 V; maximum 700 mW to active cable electronics

Safety warnings

Under USB PD 3.1 EPR, VBUS can reach 48 V — treat the VBUS rail with appropriate care in any design or repair context. 48 V DC is above the generally accepted safe low-voltage threshold.
Do not attempt to cut, strip, or re-terminate USB-C cables unless you have appropriate micro-precision tooling. USB-C connector pins have 0.5 mm pitch — incorrect termination creates short circuits between adjacent pins that are not detectable without test equipment.
ESD (electrostatic discharge) can damage USB-C controller ICs and suppress protection devices. Handle PCBs and components with ESD precautions (wrist strap, anti-static mat, grounded work surface).
A non-compliant USB-C cable or charger can deliver incorrect voltages to a sink device. Always use cables and chargers carrying verifiable USB-IF certification for the power level required. Non-certified high-wattage chargers have caused device damage and in rare cases fire.
Do not rely on cable colour or physical appearance to determine cable capability — a USB-C cable with or without SuperSpeed conductors is physically identical. Use a USB-C cable tester to verify before assuming capability.

Tools needed

USB-C cable tester (verifies all 24 pins, CC resistors, E-Marker communication)
Digital multimeter with continuity and resistance measurement (for VBUS, GND, and CC verification)
Impedance-controlled PCB design tools (for designs involving SuperSpeed or USB4 routing)
ESD wrist strap and anti-static mat (for handling connector ICs and PCBs)
Microscope or magnifier (for inspection of 0.5 mm pitch USB-C connector solder joints)
Oscilloscope with high-bandwidth probes (for SuperSpeed signal integrity testing at 10+ Gbps)

Common mistakes

Assuming all USB-C cables support USB 3.x SuperSpeed data or Alt Mode video — many low-cost cables omit the SuperSpeed conductors entirely and support only charging and USB 2.0 data.
Confusing the CC resistor scheme: placing a pull-down resistor (Rd = 5.1 kΩ) on a source/charger port instead of a pull-up resistor (Rp) — this prevents the source from advertising its current capability and the sink may default to 500 mA draw.
Routing SuperSpeed differential pairs without impedance control on a PCB — uncontrolled impedance causes reflections and signal integrity failures at USB 3.x speeds, resulting in intermittent data errors or link training failures.
Omitting ESD protection on the CC lines and VBUS — USB-C connectors are user-accessible and subject to frequent plugging cycles with static discharge risk. Unprotected CC pins and VBUS can be damaged by ESD events.
Using a USB-C to USB-C cable that lacks an E-Marker chip for EPR charging over 60 W — the PD source must detect an E-Marker confirming the cable is rated for ≥ 5 A before it will supply currents above 3 A on VBUS.

Troubleshooting

Device charges at 5 V / 900 mA regardless of charger capability: Cause: CC lines are not connected, CC resistors are incorrect, or the PD controller is not enumerating — the sink defaults to 5 V / 900 mA (USB Type-C default current) when CC negotiation fails Fix: Verify CC1 and CC2 continuity in the cable with a USB-C cable tester. Measure the pull-up voltage on CC pins at the source — should be approximately 4.5 V (10 kΩ to 5 V) for 3 A advertisement. Confirm the sink device's PD controller is enumerating by monitoring CC communication with a USB-C protocol analyser.
SuperSpeed USB 3.x data link does not establish — only USB 2.0 operates: Cause: Cable does not contain SuperSpeed conductors; SuperSpeed pair impedance is out of specification causing link training failure; connector solder joint quality issue on TX/RX pads Fix: Test the cable with a USB-C cable tester to confirm SuperSpeed conductors are present and connected. If the cable is confirmed good, check PCB routing impedance for the SuperSpeed pairs and inspect connector pad solder joints under magnification.
USB-C Alt Mode (DisplayPort video) does not work: Cause: Cable does not support Alt Mode (no SuperSpeed conductors, no SBU conductors); the host or device does not support the specific Alt Mode; the Alternate Mode negotiation on CC failed due to incorrect mux configuration Fix: Verify cable supports DP Alt Mode using a cable tester. Confirm both devices advertise DP Alt Mode capability. If hardware is confirmed compatible, check the USB-C mux/switch IC configuration on the host — it must route the SuperSpeed pairs to the DisplayPort Alt Mode path after CC negotiation selects DP mode.

Frequently asked questions

What do CC1 and CC2 do in a USB-C connector?

CC1 (A5) and CC2 (B5) are the Configuration Channel pins. They serve two functions: detecting plug orientation (when the plug is inserted one way, CC1 connects to the cable CC wire; the other way, CC2 does), and carrying the USB Power Delivery protocol — a serial communication protocol (BMC-encoded at 300 kbps) that allows a power sink to request specific voltages and currents from a power source up to 240 W under PD 3.1.

How does USB-C Power Delivery reach 240 W?

USB Power Delivery 3.1 (PD 3.1) introduced Extended Power Range (EPR), allowing VBUS to be negotiated up to 48 V at up to 5 A, giving a maximum of 240 W. The negotiation occurs over the CC lines using structured message exchanges. Both the power source and sink must support PD 3.1 EPR and the cable must be an EPR-rated electronically marked cable (E-Marker). Standard PD 3.0 is limited to 20 V / 5 A = 100 W.

What is an electronically marked USB-C cable?

Electronically marked (E-Marker) cables contain a small chip in the plug housing, powered via the VCONN pin, that communicates the cable's capabilities — maximum current rating, USB version support, and whether it supports EPR — to both connected devices via the CC wire. Devices read this information before applying higher power levels. Non-E-Marker cables default to 3 A maximum by convention.

Can all USB-C cables carry video (DisplayPort Alt Mode)?

No. DisplayPort Alternate Mode (DP Alt Mode) repurposes the SuperSpeed lanes and SBU pins to carry DisplayPort signals. The cable must be certified for DP Alt Mode and the devices at both ends must support it. A USB-C to DisplayPort cable or a Thunderbolt 3/4 cable typically supports DP Alt Mode. A basic USB 2.0 charging-only USB-C cable has no SuperSpeed conductors and cannot carry video.

Why does a USB-C cable sometimes support only USB 2.0 speeds?

Many low-cost USB-C cables omit the SuperSpeed differential pair conductors entirely, implementing only VBUS, GND, CC, and D+/D−. These cables support charging and USB 2.0 data (480 Mbps) but cannot carry USB 3.x SuperSpeed data or video. An electronically marked cable or one sold with a specific USB 3.x or Thunderbolt certification is guaranteed to have the full conductor set.

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