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USB-C From Wikipedia - Specifications

Specifications[edit]

USB Type-C Cable and Connector Specification[edit]

The USB Type-C specification 1.0 was published by the USB Implementers Forum (USB-IF) and was finalized in August 2014.[3]

It defines requirements for cables and connectors.

Adoption as IEC specification:

Receptacles[edit]

The receptacle features four power and four ground pins, two differential pairs for high-speed USB data (though they are connected together on devices), four shielded differential pairs for Enhanced SuperSpeed data (two transmit and two receive pairs), two Sideband Use (SBU) pins, and two Configuration Channel (CC) pins.

USB-C receptacle A pin layout
PinNameDescription
A1GNDGround return
A2SSTXp1SuperSpeed differential pair #1, TX, positive
A3SSTXn1SuperSpeed differential pair #1, TX, negative
A4VBUSBus power
A5CC1Configuration channel
A6Dp1USB 2.0 differential pair, position 1, positive
A7Dn1USB 2.0 differential pair, position 1, negative
A8SBU1Sideband use (SBU)
A9VBUSBus power
A10SSRXn2SuperSpeed differential pair #4, RX, negative
A11SSRXp2SuperSpeed differential pair #4, RX, positive
A12GNDGround return

 

USB-C receptacle B pin layout
PinNameDescription
B12GNDGround return
B11SSRXp1SuperSpeed differential pair #2, RX, positive
B10SSRXn1SuperSpeed differential pair #2, RX, negative
B9VBUSBus power
B8SBU2Sideband use (SBU)
B7Dn2USB 2.0 differential pair, position 2, negative[a]
B6Dp2USB 2.0 differential pair, position 2, positive[a]
B5CC2Configuration channel
B4VBUSBus power
B3SSTXn2SuperSpeed differential pair #3, TX, negative
B2SSTXp2SuperSpeed differential pair #3, TX, positive
B1GNDGround return

USB-C receptacle pinout end-on view
Notes[edit]
  1. Jump up to:a b There is only a single non-SuperSpeed differential pair in the cable. This pin is not connected in the plug/cable.

Plugs[edit]

The male connector (plug) has only one high-speed differential pair, and one of the CC pins is replaced by VCONN, to power electronics in the cable, and the other is used to actually carry the Configuration Channel signals. These signals are used to determine the orientation of the cable, as well as to carry USB Power Delivery communications.

USB-C plug pinout end-on view

Cables[edit]

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 colorNoNameDescription2.0[a]PinName
ShellShieldBraidBraidShieldCable external braidShellShield
A1, B12, 
B1, A12
GNDTin-plated1GND_PWRrt1Ground for power returnA1, B12, 
B1, A12
GND
16GND_PWRrt2
A4, B9, 
B4, A9
VBUSRed2PWR_VBUS1VBUS powerA4, B9, 
B4, A9
VBUS
17PWR_VBUS2
B5VCONNYellow 
18PWR_VCONNVCONN power, for powered cables[b]B5VCONN
A5CCBlue3CCConfiguration channelA5CC
A6Dp1White4UTP_Dp[c]Unshielded twisted pair, positiveA6Dp1
A7Dn1Green5UTP_Dn[c]Unshielded twisted pair, negativeA7Dn1
A8SBU1Red14SBU_ASideband use AB8SBU2
B8SBU2Black15SBU_BSideband use BA8SBU1
A2SSTXp1Yellow[d]6SDPp1Shielded differential pair #1, positiveB11SSRXp1
A3SSTXn1Brown[d]7SDPn1Shielded differential pair #1, negativeB10SSRXn1
B11SSRXp1Green[d]8SDPp2Shielded differential pair #2, positiveA2SSTXp1
B10SSRXn1Orange[d]9SDPn2Shielded differential pair #2, negativeA3SSTXn1
B2SSTXp2White[d]10SDPp3Shielded differential pair #3, positiveA11SSRXp2
B3SSTXn2Black[d]11SDPn3Shielded differential pair #3, negativeA10SSRXn2
A11SSRXp2Red[d]12SDPp4Shielded differential pair #4, positiveB2SSTXp2
A10SSRXn2Blue[d]13SDPn4Shielded differential pair #4, negativeB3SSTXn2
  1. ^ USB 2.0 Type-C cables do not include wires for SuperSpeed or sideband use.

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

  3. Jump up to:a b 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.

  4. Jump up to:a b c d e f g h Wire colors for differential pairs are not mandated.

Related USB-IF specifications[edit]

USB Type-C Locking Connector Specification[edit]

The USB Type-C Locking Connector Specification was published 2016-03-09. It defines the mechanical requirements for USB-C plug connectors and the guidelines for the USB-C receptacle mounting configuration to provide a standardized screw lock mechanism for USB-C connectors and cables.[23]

USB Type-C Port Controller Interface Specification[edit]

The USB Type-C Port Controller Interface Specification was published 2017-10-01. It defines a common interface from a USB-C Port Manager to a simple USB-C Port Controller.[24]

USB Type-C Authentication Specification[edit]

Adopted as IEC specification:

USB 2.0 Billboard Device Class Specification[edit]

USB 2.0 Billboard Device Class is defined to communicate the details of supported Alternate Modes to the computer host OS. It provides user readable strings with product description and user support information. Billboard messages can be used to identify incompatible connections made by users. They are not required to negotiate Alternate Modes and only appear when negotiation fails between the host (source) and device (sink).

USB Audio Device Class 3.0 Specification[edit]

USB Audio Device Class 3.0 defines powered digital audio headsets with a USB-C plug.[6] The standard support the transfer of both digital and analog audio signals over the USB port.[26]

USB Power Delivery Specification[edit]

While it is not necessary for USB-C compliant devices to implement USB Power Delivery, for USB-C DRP/DRD (Dual-Role-Power/Data) ports, USB Power Delivery introduces commands for altering a port's power or data role after the roles have been established when a connection is made.[27]

USB 3.2 Specification[edit]

USB 3.2, released in September 2017, replaces the USB 3.1 standard. It preserves existing USB 3.1 SuperSpeed and SuperSpeed+ data modes and introduces two new SuperSpeed+ transfer modes over the USB-C connector using two-lane operation, with data rates of 10 and 20 Gbit/s (1250 and 2500 MB/s).

Alternate Mode partner specifications[edit]

As of 2018, five system-defined Alternate Mode partner specifications exist. Additionally, vendors may support proprietary modes for use in dock solutions. Alternate Modes are optional; USB-C features and devices are not required to support any specific Alternate Mode. The USB Implementers Forum is working with its Alternate Mode partners to make sure that ports are properly labelled with respective logos.[28]

List of Alternate Mode partner specifications
LogoNameDateProtocol
DP from DisplayPort.svgDisplayPort Alternate ModePublished in September 2014DisplayPort 1.4[29][30]
Mobile High-Definition Link (logo).svgMobile High-Definition Link (MHL) Alternate ModeAnnounced in November 2014[31]MHL 1.0, 2.0, 3.0 and superMHL 1.0[32][33][34][35]
ThunderboltFulmine.svgThunderbolt Alternate ModeAnnounced in June 2015[36]Thunderbolt 3 (also carries DisplayPort 1.2 or DisplayPort 1.4)[36][37][38][39]
High Definition Multimedia Interface Logo.svgHDMI Alternate ModeAnnounced in September 2016[40]HDMI 1.4b[41][42][43][44]

VirtualLink Alternate ModeAnnounced in July 2018[45]VirtualLink 1.0 (not yet standardized)[46]
Table showing various protocols supported by USB-C

Other protocols like Ethernet[47] have been proposed.

All Thunderbolt 3 controllers both support "Thunderbolt Alternate Mode" and "DisplayPort Alternate Mode".[48] Because Thunderbolt can encapsulate DisplayPort data, every Thunderbolt controller can either output DisplayPort signals directly over "DisplayPort Alternative Mode" or encapsulated within Thunderbolt in "Thunderbolt Alternate Mode". Low cost peripherals mostly connect via "DisplayPort Alternate Mode" while some docking stations tunnel DisplayPort over Thunderbolt.[49]

The USB SuperSpeed protocol is similar to DisplayPort and PCIe/Thunderbolt, in using packetized data transmitted over differential LVDS lanes with embedded clock using comparable bit rates, so these Alternate Modes are easier to implement in the chipset.[29]

Alternate Mode hosts and sinks can be connected with either regular full-featured USB-C cables, or converter cables/adapters:

Active cables/adapters contain powered ICs to amplify/equalise the signal for extended length cables, or to perform active protocol conversion. The adapters for video Alt Modes may allow conversion from native video stream to other video interface standards (e.g., DisplayPort, HDMI, VGA or DVI).

Using full-featured USB-C cables for Alternate Mode connections provides some benefits. Alternate Mode does not employ USB 2.0 lanes and the configuration channel lane, so USB 2.0 and USB Power Delivery protocols are always available. In addition, DisplayPort and MHL Alternate Modes can transmit on one, two, or four SuperSpeed lanes, so two of the remaining lanes may be used to simultaneously transmit USB 3.1 data.[52]

Alternate Mode protocol support matrix for USB-C cables and adapters
ModeUSB 3.1 Type-C cable[a]Adapter cable or adapterConstruction
USB[b]DisplayPortThunderboltsuperMHLHDMIHDMIDVI-DComponent video
3.11.21.420 Gbit/s40 Gbit/s1.4b1.4b2.0bsingle-linkdual-link(YPbPr, VGA/DVI-A)
DisplayPortYesYes
NoPassive

OptionalYesYesYesActive
ThunderboltYes[c]Yes[c]YesYes[d]
NoPassive

OptionalOptionalYesYesYesYesActive
MHLYes
Yes
YesNoYesNoNoPassive

Optional
Yes
YesActive
HDMI
YesYesNoYesNoNoPassive
Optional
YesActive
  1. ^ USB 2.0 and USB Power Delivery are available at all times in a Type-C cable

  2. ^ USB 3.1 can be transmitted simultaneously when the video signal bandwidth requires two or fewer lanes.

  3. Jump up to:a b Is only available in Thunderbolt 3 DisplayPort mode.

  4. ^ Thunderbolt 3 40 Gbit/s passive cables are only possible <0.5 m due to limitations of current cable technology.

USB-C receptacle pin usage in different modes[edit]

The diagrams below depict the pins of a USB-C socket in different use cases.

USB 2.0/1.1[edit]

A simple USB 2.0/1.1 device mates using one pair of D+/D− pins. Hence, the source (host) does not require any connection management circuitry, and therefore USB-C is backward compatible with even the oldest USB devices. VBUS and GND provide 5 V up to 500 mA of current. However, to connect a USB 2.0/1.1 device to a USB-C host, use of Rd[53] on the CC pins is required, as the source (host) will not supply VBUS until a connection is detected through the CC pins.

GNDTX1+TX1−VBUSCC1D+D−SBU1VBUSRX2−RX2+GND
GNDRX1+RX1−VBUSSBU2D−D+CC2VBUSTX2−TX2+GND

USB Power Delivery[edit]

USB Power Delivery uses one of CC1, CC2 pins for power negotiation up to 20 V at 5 A (or whatever less the source can provide). It is transparent to any data transmission mode, and can therefore be used together with any of them.

GNDTX1+TX1−VBUSCC1D+D−SBU1VBUSRX2−RX2+GND
GNDRX1+RX1−VBUSSBU2D−D+CC2VBUSTX2−TX2+GND

USB 3.0/3.1/3.2[edit]

In the USB 3.0/3.1/3.2 mode, two or four high speed links are used in TX/RX pairs to provide 5 to 20 Gbit/s throughput. One of the CC pins is used to negotiate the mode.

VBUS and GND provide 5 V up to 900 mA, in accordance with the USB 3.1 specification. A specific USB-C mode may also be entered, where 5 V up to 3 A is provided.[54] A third alternative is to establish a Power Delivery contract.

The D+/D− link for USB 2.0/1.1 is typically not used when USB 3.x connection is active, but devices like hubs open simultaneous 2.0 and 3.x uplinks in order to allow operation of both type devices connected to it. Other devices may have fallback mode to 2.0, in case the 3.x connection fails.

GNDTX1+TX1−VBUSCC1D+D−SBU1VBUSRX2−RX2+GND
GNDRX1+RX1−VBUSSBU2D−D+CC2VBUSTX2−TX2+GND

Alternate Mode[edit

In the Alternate Mode one of up to four high speed links are used in whatever direction is needed. SBU1, SBU2 provide an additional lower speed link. If two high speed links remain unused, then a USB 3.0/3.1 link can be established concurrently to the Alternate Mode.[30] One of the CC pins is used to perform all the negotiation. An additional low band bidirectional channel (other than SBU) may share that CC pin as well.[30][41] USB 2.0 is also available through D+/D− pins.

In regard to power, the devices are supposed to negotiate a Power Delivery contract before an alternate mode is entered.[55]

GNDTX1+TX1−VBUSCC1D+D−SBU1VBUSRX2−RX2+GND
GNDRX1+RX1−VBUSSBU2D−D+CC2VBUSTX2−TX2+GND

Debug Accessory Mode[edit]

The external device test system signals to the target system to enter debug accessory mode via CC1 and CC2 both being pulled down with an Rn resistor value or pulled up as Rp resistor value from the test plug (Rp and Rn specified in Type-C spec).

After entering debug accessory mode, optional orientation detection via the CC1 and CC2 is done via setting CC1 as a pullup of Rd resistance and CC2 pulled to ground via Ra resistance (From the test system type-c plug). While optional, orientation detection is required if you want usb power delivery communication to be functional.

In this mode, all digital circuits are disconnected from the connector, and 14 underlined pins can be used to expose debug related signals (e.g. JTAG interface). USB IF requires for certification that security and privacy consideration and precaution has been taken and that the user has actually requested that debug test mode be performed.

GNDTX1+TX1−VBUSCC1D+D−SBU1VBUSRX2−RX2+GND
GNDRX1+RX1−VBUSSBU2D−D+CC2VBUSTX2−TX2+GND

If a reversible Type-C cable is required but Power Delivery support is not, the test plug will need to be arranged as below, with CC1 and CC2 both being pulled down with an Rn resistor value or pulled up as Rp resistor value from the test plug:

GNDTS1TS2VBUSCC1TS6TS7TS5VBUSTS4TS3GND
GNDTS3TS4VBUSTS5TS7TS6CC2VBUSTS2TS1GND

This mirroring of test signals will only provide 7 test signals for debug usage instead of 14, but with the benefit of minimising extra parts count for orientation detection.

Audio Adapter Accessory Mode[edit]

In this mode, all digital circuits are disconnected from the connector, and certain pins become reassigned for analog outputs or inputs. The mode, if supported, is entered when both CC pins are shorted to GND. D- and D+ become audio output left L and right R, respectively. The SBU pins become a microphone pin MIC, and the analog ground AGND, the latter being a return path for both outputs and the microphone. Nevertheless, the MIC and AGND pins must have automatic swap capability, for two reasons: firstly, the USB-C plug may be inserted either side; secondly, there is no agreement, which TRRS rings shall be GND and MIC, so devices equipped with a headphone jack with microphone input must be able to perform this swap anyway.[56]

This mode also allows concurrent charging of a device exposing the analog audio interface (through VBUS and GND), however only at 5 V and 500 mA, as CC pins are unavailable for any negotiation.

GNDTX1+TX1−VBUSCC1RLMICVBUSRX2−RX2+GND
GNDRX1+RX1−VBUSAGNDLRCC2VBUSTX2−TX2+GND

Plug insertions detection is performed by the TRRS plug's physical plug detection switch. On plug insertions, this will pull down both CC and VCONN in the plug (CC1 and CC2 in the receptacle). This resistance must be less than 800 ohms which is the minimum "Ra" resistance specified in the USB Type-C specification). This is essentially a direct connection to USB digital ground.

TRRS rings wiring to Type-C male plug (Figure A-2 of USB Type-C Cable and Connector Specification Release 1.3)
TRRS SocketAnalog Audio SignalUSB Type-C male plug
TipLD- (Data -)
Ring1RD+ (Data +)
Ring2MIC/GNDSBUS1 or SBUS2
SleeveMIC/GNDSBUS2 or SBUS1
DETECT1Plug presence detection switchCC & VCONN
DETECT2Plug presence detection switchGND

Software support[edit]

Hardware support[edit]

USB-C devices[edit]

An increasing number of motherboards, notebooks, tablet computers, smartphones, hard disk drives, USB hubs and other devices released from 2014 onwards feature USB-C receptacles. However, further adoption of USB-C is limited by the comparatively high cost of USB-C cables and connectors.[66]

Currently, DisplayPort is the most widely implemented alternate mode, and is used to provide video output on devices that do not have standard-size DisplayPort or HDMI ports, such as smartphones and laptops. A USB-C multiport adapter converts the device's native video stream to DisplayPort/HDMI/VGA, allowing it to be displayed on an external display, such as a television set or computer monitor.

Examples of devices that support DisplayPort Alternate Mode over USB-C include: MacBookChromebook PixelSurface Book 2Samsung Galaxy TabPro SSamsung Galaxy Tab S4iPad Pro (3rd generation)Essential PhoneROG PhoneRazer Phone/2HTC 10/U UltraHuawei Mate 10/20Samsung Galaxy S8/S9Microsoft Lumia 950LG V20 etc.

Examples of devices that support high-power charging according to the USB Power Delivery specification include: MacBookChromebook PixelSurface Book 2, Dell Venue 10 Pro, Lenovo ThinkPad X1, Samsung Galaxy TabPro SSamsung Galaxy Tab S4iPad ProNintendo SwitchNexus 5X/6PGoogle Pixel/2ROG PhoneBlackBerry Key2Essential PhoneHTC 10/U UltraLG G5/G6Moto ZNokia 8Razer PhoneSamsung Galaxy S8/S9Samsung Galaxy Note 8/Note 9,Sony Xperia XZ1/XZ2Apple iPhone 8/X etc.

USB-C cables[edit]

Many cables claiming to support USB-C are actually not compliant to the standard. Using these cables would have a potential consequence of damaging devices that they are connected to.[67][68][69] There are reported cases of laptops being destroyed due to the use of non-compliant cables.[70]

Power issues[edit]

Some non-compliant cables with a USB-C connector on one end and a legacy USB-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 56 kΩ pullup,[71]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.[72][73]

Compatibility issues[edit]

Compatibility with audio adapters[edit]

On devices that have omitted the 3.5 mm audio jack, the USB-C port can be used to connect wired accessories such as headphones.

There are primarily two types of USB-C adapters (active adapters with DACs, passive adapters without DACs) and two modes of audio output from devices (phones without onboard DACs that send out digital audio, phones with onboard DACs that send out analog audio).[74][75]

When an active set of USB-C headphones or adapter is used, digital audio is sent through the USB-C port. The conversion by the DAC and amplifier is done inside of the headphones or adapter, instead of on the phone. The sound quality is dependent on the headphones/adapter's DAC. Active adapters with a built-in DAC have near-universal support for devices that output digital and analog audio, adhering to the Audio Device Class 3.0 and Audio Adapter Accessory Mode specifications.

Examples of such active adapters include external USB sound cards/DACs that do not require special drivers,[76] and USB-C to 3.5 mm headphone jack adapters by Apple, Google, Essential, Razer, HTC.[77]

On the other hand, when a passive set of USB-C headphones or adapter is used, analog audio is sent through the USB-C port. The conversion by the DAC and amplifier is done on the phone; the headphones or adapter simply passthrough the signal. The sound quality is dependent on the phone's onboard DAC. Passive adapters without a built-in DAC are only compatible with devices that output analog audio, adhering to the Audio Adapter Accessory Mode specification.

USB-C to 3.5 mm audio adapters and USB sound cards compatibility
Supported modeSpecificationDevicesUSB-C adapters with DACs (active adapters)USB-C adapters without DACs (passive adapters)
Digital audio outputAudio Device Class 3.0 (digital audio)Google Pixel 2, HTC U11, 
Essential Phone, Razer Phone etc.

Digital-to-analog conversion by adapter

Incompatible (conversion required)

Analog audio outputAudio Device Class 3.0 (digital audio)

Audio Adapter Accessory Mode (analog audio)

Moto Z2 Force, Sony Xperia XZ2, 
Huawei P20 Pro, LeEco, Xiaomi phones etc.

Digital-to-analog conversion by adapter

Analog passthrough (no conversion)

Compatibility with other fast charging technology[edit]

In 2016, Benson Leung, an engineer at Google, pointed out that Quick Charge 2.0 and 3.0 technologies developed by Qualcomm are not compatible with the USB-C standard.[78] Qualcomm responded that it is possible to make fast charge solutions fit the voltage demands of USB-C and that there are no reports of problems; however, it did not address the standard compliance issue at that time.[79] Later in the year, Qualcomm released Quick Charge 4 technology, which cited – as an advancement over previous generations – "USB Type-C and USB PD compliant".[80]