USB Type-C

January 12 ,2017 USB Type-C Professional Knowledge USB Type-C is a USB specification for a small 24-pin fully reversible-plug connector for USB devices and USB cabling.

USB Type-C is a USB specification for a small 24-pin fully reversible-plug connector for USB devices and USB cabling.

The USB Type-C Specification 1.0 was published by the USB Implementers Forum (USB-IF) and was finalized in August 2014. It was developed at roughly the same time as the USB 3.1 specification.

If a product implements USB Type-C, it does not necessarily support USB 3.1 or USB Power Delivery.



USB Type-C on a MacBook                 The 24-pin USB Type-C plug



The USB  Type-C connectors connect to both hosts and devices, replacing various  Type-B and Type-A connectors and cables with a standard meant to be future-proof. The 24-pin double-sided connector is slightly larger than the micro-B connector,  with a USB Type-C port measuring 8.4 millimetres (0.33 in) by 2.6  millimetres (0.10 in). The connector provides four power/ground pairs,  two differential pairs for non-SuperSpeed data (though only one pair is  populated in a USB Type-C cable), four pairs for SuperSpeed data bus  (twice as much as on the USB3 connector), two "sideband use" pins, and  two configuration pins for cable orientation detection, dedicated biphase mark code (BMC) configuration data channel, and VCONN +5 V power for active cables. Connecting an older device to a host with a USB Type-C receptacle  requires a cable or adapter with a Type-A or Type-B plug or receptacle  on one end and a USB Type-C plug on the other end. Legacy adapters with a  USB Type-C receptacle are "not defined or allowed" by the  specification, due to their being able to create "many invalid and  potentially unsafe" cable combinations.

USB 3.1 Type-C to Type-C cables are considered full-featured USB Type-C cables and must be active,  electronically marked cables that contain a chip with an ID function  based on the configuration channel and vendor-defined messages (VDMs)  from the USB Power Delivery 2.0  specification. USB Type-C devices may optionally support bus power  currents of 1.5 A and 3.0 A (at 5 V) in addition to baseline bus power  provision; power sources can either advertise increased USB current  through the configuration channel, or they can support the full power  delivery specification using both BMC-coded configuration line and  legacy BFSK-coded VBUS  line. USB 2.0 Type-C to Type-C cables are only required to contain  e-marker chips if the cable supports 5A instead of the default 3A, which  requires USB Power Delivery support.

Devices may be hosts or peripherals. Some, such as mobile phones,  can take either role depending on what kind is detected on the other  end. These types of ports are called Dual-Role-Data (DRD). When two such  devices are connected, the roles are randomly assigned but a swap can  be commanded from either end. Furthermore, dual-role devices that  support USB Power Delivery  may independently and dynamically swap data and power roles using the  Data Role Swap or Power Role Swap processes. This allows for  charge-through hub or docking station applications where the Type-C device acts as a USB data host while acting as a power consumer rather than a source.

Alternate Mode


 USB Type C cable

An Alternate Mode dedicates some of the physical wires in the USB  Type-C cable for direct device-to-host transmission of alternate data  protocols. The four high-speed lanes, two sideband pins, and (for dock,  detachable device and permanent cable applications only) two  non-SuperSpeed data pins and one configuration pin can be used for  alternate mode transmission. The modes are configured using VDMs through  the configuration channel.

List of Alternate Mode partner specifications
DisplayPort Alternate ModeDP from DisplayPort.pngpublished in September 2014DisplayPort 1.3 (includes USB 3.1).
MHL Alternate ModeNew MHL Logo.jpgannounced in November 2014MHL 1.0, 2.0, 3.0 and superMHL.
Thunderbolt Alternate ModeThunderboltFulmine.svgannounced in June 2015 Thunderbolt 3 (includes DisplayPort Alternate Mode).
HDMI Alternate ModeHDMI Logo.svgannounced in September 2016HDMI 1.4b.

Other serial protocols like PCI Express and Base-T Ethernet are possible.

Compliant Alternate Mode hosts and sinks can be connected with  regular passive USB 3.1 Type-C cables or passive converter  cables/adapters:

  • USB 3.1 Type-C cable

  • Alternate Mode DisplayPort, MHL, HDMI and Thunderbolt 20 Gbps ports  can be interconnected with standard "full-featured" USB 3.1 Type-C  cables. Thunderbolt3 (40Gbps) protocol requires specially tested reduced  length cables that are certified and electronically marked for  high-speed, similarly to high-power USB Power Delivery.

  • USB 3.1 Type-C adapter cable (plug) or adapter (socket)

  • These cables/adapters typically contain a DisplayPort plug, HDMI plug or socket, or superMHL plug on the other end.

Alternate Mode does not use USB 2.0 lanes and configuration channel  pin, so USB 2.0 and USB Power Delivery protocols are always available.  DisplayPort (Thunderbolt 3) Alternate Mode can simultaneously trasmist  USB 3.1 signal using two of the four SuperSpeed lanes.

A Type-C device is not required to support any Alternate Mode. The  USB Implementers Forum is working with its Alternate Mode partners to  make sure that ports are properly labelled with respective logos.

Protocol conversion requires active cables/adapters which contain  powered ICs. DisplayPort Alternate Mode (and DisplayPort Alternate Mode  support within the Thunderbolt 3 Alternate Mode) can be used for active  conversion to Analog VGA, component video, dual-link DVI, and HDMI; passive HDMI 2.0 conversion using Dual-Mode DisplayPort (DP++) is not supported. MHL Alternate Mode can be used for active conversion to HDMI. HDMI Alternate Mode does not define protocol conversion.

As of December 2016, existing USB Type-C ports and  USB-HDMI/USB-DisplayPort convertors use regular USB 2.0/3.1 protocols;  Type-C Alternate Mode compliant products are expected to appear during  H1 2017.

Connector pinouts and cable wiring

Connector pinouts

Type-C plug and receptacle pinouts

A1GNDGround returnB12GNDGround return

A2SSTXp1SuperSpeed differential pair #1, TX, positiveB11SSRXp1SuperSpeed differential pair #2, RX, positive

A3SSTXn1SuperSpeed differential pair #1, TX, negativeB10SSRXn1SuperSpeed differential pair #2, RX, negative

A4VBUSBus powerB9VBUSBus power

A5CC1Configuration channelB8SBU2Sideband use (SBU)

A6Dp1Non-SuperSpeed differential pair, position 1, positiveB7Dn2Non-SuperSpeed differential pair, position 2, negative

A7Dn1Non-SuperSpeed differential pair, position 1, negativeB6Dp2Non-SuperSpeed differential pair, position 2, positive

A8SBU1Sideband use (SBU)B5CC2Configuration channel

A9VBUSBus powerB4VBUSBus power

A10SSRXn2SuperSpeed differential pair #4, RX, negativeB3SSTXn2SuperSpeed differential pair #3, TX, negative

A11SSRXp2SuperSpeed differential pair #4, RX, positiveB2SSTXp2SuperSpeed differential pair #3, TX, positive

A12GNDGround returnB1GNDGround return

  1. There is only a single Non-SuperSpeed differential pair in the cable. This pin is not connected in the plug/cable.


 USB Type-C receptacle pinout end-on view


 USB Type-C plug pinout end-on view

Cable wiring

The  capabilities of USB Type-C cables depends on (1) USB modes supported,  (2) Amount of power supported for charging and (3) Alternate modes  supported by the cable. There are cables which support only USB 2.0 with up to 480 Mbps data rate. The cables which support USB 3.0/USB 3.1 Gen 1 can handle up to 5 Gbps data rate at full duplex and are marked as super-speed cable. The cables which support USB 3.1  Gen 2 handle up to 10 Gbps data rate at full duplex and are marked as  super-speed+. The charging capacity of USB Type-C cables may go up to 5A  (100W), but 3A (i.e. up to 60W) cables are commonly available.

The support for alternate modes requires extra connections for  optional pins as well - like additional super-speed lanes, and  'side-band use' pins. The support for alternate modes usually adds an  extra bandwidth requirement to the cable - in addition to the bandwidth  already needed for USB data transfer. For example:

  • A USB 3.1 Gen 2 super-speed+ cable supporting 10 Gbps data rate has  an aggregate bandwidth capacity of 20 Gbps (i.e. 10 Gbps transmit + 10  Gbps receive).

  • A USB 3.0 data stream of 5 Gbps has a bandwidth requirement of 10 Gbps (i.e. 5 Gbps transmit + 5 Gbps receive).

  • A 4K UHD 30fps video stream has a bandwidth requirement of 10 Gbps.

  • A 4K UHD 60fps video stream has a bandwidth requirement of 18 Gbps.

Hence, a USB 3.1 super-speed+ cable can safely carry a simultaneous 5  Gbps data stream and 4K UHD 30fps video stream at once (i.e. 10 Gbps  data stream + 10 Gbps video stream roughly fits in to 20 Gbps cable  capacity). Or it can carry a 4K UHD 60fps video stream alone. There are USB-IF certification programs available for USB Type-C cables and it is recommended to use USB-IF certified cables.

Full-featured USB 3.1 and 2.0 Type-C cable wiring
Plug 1, USB Type-CUSB Type-C cablePlug 2, USB Type-C
PinNameWire colourNoNameDescription2.0PinName
ShellShieldBraidBraidShieldCable external braidShellShield
A1, B12,
B1, A12
GNDTin-plated1GND_PWRrt1Ground for power returnA1, B12,
B1, A12
A4, B9,
B4, A9
B4, A9
18PWR_VCONNVCONN power, for active cablesB5VCONN
A5CCBlue3CCConfiguration channelA5CC
A6Dp1White4UTP_DpUnshielded twisted pair, positiveA6Dp1
A7Dn1Green5UTP_DnUnshielded twisted pair, negativeA7Dn1
A8SBU1Red14SBU_ASideband use AB8SBU2
B8SBU2Black15SBU_BSideband use BA8SBU1
A2SSTXp1Yellow6SDPp1Shielded differential pair #1, positiveB11SSRXp1
A3SSTXn1Brown7SDPn1Shielded differential pair #1, negativeB10SSRXn1
B11SSRXp1Green8SDPp2Shielded differential pair #2, positiveA2SSTXp1
B10SSRXn1Orange9SDPn2Shielded differential pair #2, negativeA3SSTXn1
B2SSTXp2White10SDPp3Shielded differential pair #3, positiveA11SSRXp2
B3SSTXn2Black[d]11SDPn3Shielded differential pair #3, negativeA10SSRXn2
A11SSRXp2Red12SDPp4Shielded differential pair #4, positiveB2SSTXp2
A10SSRXn2Blue[d]13SDPn4Shielded differential pair #4, negativeB3SSTXn2

  • USB 2.0 Type-C cables do not include wires for SuperSpeed, sideband use, or as great power capacity.

  • VCONN must not traverse end-to-end through the cable. Some isolation method must be used.

  • There  is only a single differential pair for non-SuperSpeed data in the  cable, which is connected to A6 and A7. Contacts B6 and B7 should not be  present in the plug.

    1. Wire colours for differential pairs are not mandated.

    Software support

    Hardware support

    An increasing number of motherboards, notebooks, tablet computers, smartphones, hard disk drives, USB hubs and other devices released from 2014 onwards feature Type-C receptacles.

    Some non-compliant cables with a Type-C connector on one end and a  legacy Standard-A plug or Micro-B receptacle on the other end  incorrectly terminate the Configuration Channel (CC) with a 10kΩ pullup  to VBUS instead of the specification mandated 56kΩ pullup, causing a device connected to the cable to incorrectly  determine the amount of power it is permitted to draw from the cable.  Cables with this issue may not work properly with certain products,  including Apple and Google products, and may even damage power sources  such as chargers, hubs, or PC USB ports.

    Relation to other specifications

    USB-IF specifications

    1. USB Type-C Locking Connector Specification

    2. USB Audio Device Class 3.0 Specification / USB Audio over USB Type-C

    3. USB Type-C Cable and Connector Language Usage Guidelines

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