| USB-C | |
| Type: | Digital audio / video / data / power – connector |
| Designer: | USB Implementers Forum |
| Design Date: | 11 August 2014 (published)[1] |
| Superseded: | All earlier USB connectors (Type-A and -B, and its different sizes: Standard, Mini, and Micro) DisplayPort Mini DisplayPort Lightning |
| Num Pins: | 24 |
USB-C, or USB Type-C, is a 24-pin connector (not a protocol) that supersedes previous USB connectors and can carry audio, video, and other data, e.g., to connect to monitors or external drives. It can also provide and receive power, to power, e.g., a laptop or a mobile phone. It is used not only by USB technology, but also by other protocols, including Thunderbolt, PCIe, HDMI, DisplayPort, and others. It is extensible to support future protocols.
The design for the USB-C connector was initially developed in 2012 by Intel, Texas Instruments and the USB Implementers Forum. The Type-C Specification 1.0 was published by the USB Implementers Forum (USB-IF) on August 11, 2014.[2] In July 2016, it was adopted by the IEC as "IEC 62680-1-3".[3]
The USB Type-C connector has 24 pins and is reversible.[4] [5] The designation "C" distinguishes it from the various USB connectors it replaced, all termed either Type-A or Type-B. Whereas earlier USB cables had a host end A and a peripheral device end B, a USB-C cable connects either way; and for interoperation with older equipment, there are cables with a Type-C plug at one end and either a Type-A (host) or a Type-B (peripheral device) plug at the other. The designation "C" refers only to the connector's physical configuration, or form factor, not to be confused with the connector's specific capabilities, such as Thunderbolt 3, DisplayPort 2.0, or USB 3.2 Gen 2x2. Based on the protocols supported by both devices, host and peripheral device, a USB-C connection normally provides (much) higher signalling and therefore data rates than the superseded connectors.
A device with a Type-C connector does not necessarily implement any USB transfer protocol, USB Power Delivery, or any of the Alternate Modes: the Type-C connector is common to several technologies while mandating only a few of them.[6]
USB 3.2, released in September 2017, fully replaced the USB 3.1 and USB 3.0 specifications. It preserves the former USB 3.1 SuperSpeed and SuperSpeed+ data transfer modes and introduces two additional data transfer modes by newly applying two-lane operations, with signalling rates of 10 Gbit/s (SuperSpeed USB 10 Gbps; raw data rate: 1.212 GB/s) and 20 Gbit/s (SuperSpeed USB 20 Gbps; raw data rate: 2.422 GB/s). They are only applicable with Full-Featured USB-C Fabrics (connectors, cables, hubs, host, and peripheral device) on all ends.
USB4, released in 2019, is the first USB transfer protocol standard that is applicable exclusively via USB-C.
The USB-C standard simplifies usage by specifying cables having identical plugs on both ends, which can be inserted without concern about orientation. When connecting two devices, the user can plug either end of the cable into either device. The plugs are flat, but will work if inserted right-side-up or upside-down.
The USB-C plugs have two-fold rotational symmetry because a plug may be inserted into a receptacle in either of two orientations. Electrically, USB-C plugs are not symmetric, as can be seen in the tables of pin layouts. Also the two ends of the USB-C are electrically different, as can be seen in the table of cable wiring. The illusion of symmetry results from how devices respond to the cable. Software makes the plugs and cables behave as though they are symmetric. According to the specifications, "Determination of this host-to-device relationship is accomplished through a Configuration Channel (CC) that is connected through the cable."[7]
The USB-C standard attempts to eliminate the need to have different cables for other communication technologies, such as Thunderbolt, PCIe, HDMI, DisplayPort, Wifi and more. USB-C cables can contain circuit boards and processors giving them much more capability than simple circuit connections.
USB-C cables interconnect hosts and peripheral devices, replacing various other electrical cables and connectors, including all earlier (legacy) USB connectors, HDMI connectors, DisplayPort ports, and 3.5 mm audio jacks.[8] [9]
USB Type-C and USB-C are trademarks of the USB Implementers Forum.[10]
The 24-pin double-sided connector is slightly larger than the micro-B connector, with a USB-C receptacle measuring 8.4mm wide, 2.6mm high, and 6.65mm deep.
Type-C cables can be split among various categories and subcategories. The first one is USB 2.0 or Full-Featured. Like the names imply, USB 2.0 Type-C cables have very limited wires and are only good for USB 2.0 communications and power delivery. They are also called charging cables colloquially. Whereas Full-Featured cables need to have all wires populated and in general support Alt modes and are further distinguished by their speed rating.
Full-Featured cables exist in 4 different speed grades. Their technical names use the "Gen A" notation, each higher number increasing capabilities in terms of bandwidth. The user-facing names are based on the bandwidth a user can typically expect "USB 5Gbps", "USB 20Gbps", "USB 40Gbps" and so on. This bandwidth notation considers the various USB standards and how they use the cable. A Gen 1 / 5 Gbit/s cable supports that bandwidth on every one of its 4 wire pairs. So technically it could be used to establish a USB3 Gen 1x2 connection with nominally 10 Gbit/s between two "SuperSpeed USB 20 Gbps" capable hosts. For a similar reason, the "USB 10Gbps" name is deprecated, as that is using only 2 of the 4 wire-pairs of a Gen 2 cable and thus synonymous with "USB 20Gbps" cables. The signal quality that the "Gen A" notation guarantees or requires is not uniform across all USB standards. See table for details.
The USB Implementers Forum certifies valid cables so they can be marked accordingly with the official logos and users can distinguish them from non-compliant products.[11] There have been simplifications in the logos.[12] Previous logos and names also referenced specific USB protocols like SuperSpeed for the USB3 family of connections or USB4 directly. The current official names and logos have removed those references as most full-featured cables can be used for USB4 connections as well as USB3 connections.
In order to achieve longer cable lengths, cable variants with active electronics to amplify the signals also exist. The Type-C standard mostly mandates these active cables to behave similar to passive cables with vast backwards compatibility. But they are not mandated to support all possible features and typically have no forward compatibility to future standards. Optical cables are even allowed to further reduce the backwards compatibility. For example, an active cable may not be able to use all high speed wire-pairs in the same direction (as used for DisplayPort connections), but only in the symmetric combinations expected by classic USB connections. Passive cables have no such limitations.
Every normal USB-C cable must support at least 3 A of current and up to 20 V for up to 60 W of power according to the USB PD specification. Cables are also allowed to support up to 5 A (with 20 V limit up to 100 W of power). Although the 20 V limit for 5 A cables has been deprecated in favor of 50 V. The combination of higher voltage support and 5 A current support is called and allows for up to 240 W (48 V, 5 A) of power according to the USB PD specification.
All Type-C cables except the minimal combination of USB 2.0 and only 3 A must contain E-Marker chips that identify the cable and its capabilities via the USB PD protocol. This identification data includes information about product/vendor, cable connectors, USB signalling protocol (2.0, Gen speed rating , Gen 2), passive/active construction, use of VCONN power, available VBUS current, latency, RX/TX directionality, SOP controller mode, and hardware/firmware version.[13] It also can include further vendor-defined messages (VDM) that detail support for Alt modes or vendor specific functionality outside of the USB standards.
| Cable Type | Speed | Marketing Names | Exp. max.Cable Length | USB2 | USB3 | USB4 | TB3 | DP | Power | |
|---|---|---|---|---|---|---|---|---|---|---|
| Remarks | ||||||||||
| Hi-Speed USB | ≤ 4m | USB PD:60W or 100W or 240W | ||||||||
| Gen 1 | USB 5Gbps | ≤ 2m | rowspan="2" | |||||||
| Gen 2 | USB 20Gbps(USB 10Gbps deprecated) | ≤ 1m | ||||||||
| (incl. passive TB4 & TB5) | Gen 3 & Gen 4 | USB 40GbpsUSB 80Gbps | ≤ 0.8m | (or asymm.) | rowspeed="2" | |||||
| Gen 2 | USB 20Gbps(USB 10Gbps deprecated) | < 5m | ||||||||
| (incl. active TB4) | Gen 3 | USB 40Gbps | rowspan="2" TB up to 2m | |||||||
| (incl. active TB5) | Gen 4 | USB 80Gbps | (or asymm.) | |||||||
| USB3 active | Gen 2 | |||||||||
| USB3 | Gen 2 | rowspan="3" | ||||||||
| USB4 | Gen 3 | rowspan="2" | ||||||||
| Gen 4 | (asymm. optional) | |||||||||
For any two pieces of equipment connecting over USB, one is a host (with a downstream-facing port, DFP) and the other is a peripheral device (with an upstream-facing port, UFP). Some products, such as mobile phones, can take either role, whichever is opposite that of the connected equipment. Such equipment is said to have Dual-Role-Data (DRD) capability, which was known as USB On-The-Go in the previous specification.[15] With USB-C, when two such devices are connected, the roles are first randomly assigned, but a swap can be commanded from either end, although there are optional path and role detection methods that would allow equipment to select a preference for a specific role. Furthermore, Dual-Role equipment that implements USB Power Delivery may swap data and power roles independently using the Data Role Swap or Power Role Swap processes. This allows for charge-through hub or docking station applications such as a portable computer acting as a host to connect to peripherals but being powered by the dock, or a computer being powered by a display, through a single USB-C cable.[6]
USB-C devices may optionally provide or consume 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 implement the full USB Power Delivery specification using both the BMC-coded configuration line and the legacy BFSK-coded VBUS line.[6] [16]
All older USB connectors (all Type-A and Type-B) are designated legacy. Connecting legacy and modern, USB-C equipment requires either a legacy cable assembly (a cable with any Type-A or Type-B plug on one end and a Type-C plug on the other) or, in very specific cases, a legacy adapter assembly.
An older device can connect to a modern (USB-C) host by using a legacy cable, with a Standard-B, Mini-B, or Micro-B plug on the device end and a USB-C plug on the other. Similarly, a modern device can connect to a legacy host by using a legacy cable with a USB-C plug on the device end and a Standard-A plug on the host end. Legacy adapters with USB-C receptacles are "not defined or allowed" by the specification because they can create "many invalid and potentially unsafe" cable combinations (being any cable assembly with two A ends or two B ends). However, exactly two types of adapter with USB-C plugs are defined: one with a Standard-A receptacle (for connecting a legacy device (such as a flash drive—not a cable) to a modern host, and supporting up to USB 3.1), and one with a Micro-B receptacle (for connecting a modern device to a legacy host, and supporting up to USB 2.0).
A device with a USB-C port may support analog headsets through an audio adapter with a 3.5 mm jack, providing three analog audio channels (left and right output and microphone). The audio adapter may optionally include a USB-C charge-through port to allow 500 mA device charging. The engineering specification states that an analog headset shall not use a USB-C plug instead of a 3.5 mm plug. In other words, headsets with a USB-C plug should always support digital audio (and optionally the accessory mode).[17]
Analog signals use the USB 2.0 differential pairs (Dp and Dn for Right and Left) and the two side-band use pairs for Mic and GND. The presence of the audio accessory is signaled through the configuration channel and VCONN.
An Alternate Mode dedicates some of the physical wires in a USB-C cable for direct device-to-host transmission using non-USB data protocols, such as DisplayPort or Thunderbolt. The four high-speed lanes, two side-band pins, and (for dock, detachable device and permanent-cable applications only) five additional pins can be used for Alternate Mode transmission. The modes are configured using vendor-defined messages (VDM) through the configuration channel.
The USB Type-C specification 1.0 was published by the USB Implementers Forum (USB-IF) and was finalized in August 2014.[9]
It defines requirements for cables and connectors.
Adoption as IEC specification:
The receptacle features four power and four ground pins, two differential pairs (connected together on devices) for legacy USB 2.0 high-speed data, 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.
| Name | Description | ||
|---|---|---|---|
| A1 | GND | Ground return | |
| A2 | SSTXp1 ("TX1+") | SuperSpeed differential pair #1, transmit, positive | |
| A3 | SSTXn1 ("TX1-") | SuperSpeed differential pair #1, transmit, negative | |
| A4 | VBUS | Bus power | |
| A5 | CC1 | Configuration channel | |
| A6 | D+ | USB 2.0 differential pair, position 1, positive | |
| A7 | D− | USB 2.0 differential pair, position 1, negative | |
| A8 | SBU1 | Sideband use (SBU) | |
| A9 | VBUS | Bus power | |
| A10 | SSRXn2 ("RX2-") | SuperSpeed differential pair #4, receive, negative | |
| A11 | SSRXp2 ("RX2+") | SuperSpeed differential pair #4, receive, positive | |
| A12 | GND | Ground return |
| Name | Description | ||
|---|---|---|---|
| B12 | GND | Ground return | |
| B11 | SSRXp1 ("RX1+") | SuperSpeed differential pair #2, receive, positive | |
| B10 | SSRXn1 ("RX1-") | SuperSpeed differential pair #2, receive, negative | |
| B9 | VBUS | Bus power | |
| B8 | SBU2 | Sideband use (SBU) | |
| B7 | D− | USB 2.0 differential pair, position 2, negative | |
| B6 | D+ | USB 2.0 differential pair, position 2, positive | |
| B5 | CC2 | Configuration channel | |
| B4 | VBUS | Bus power | |
| B3 | SSTXn2 ("TX2-") | SuperSpeed differential pair #3, transmit, negative | |
| B2 | SSTXp2 ("TX2+") | SuperSpeed differential pair #3, transmit, positive | |
| B1 | GND | Ground return |
The plug has only one USB 2.0 high-speed differential pair, and one of the CC pins (CC2) is replaced by VCONN, to power optional electronics in the cable, and the other is used to actually carry the Configuration Channel (CC) signals. These signals are used to determine the orientation of the cable, as well as to carry USB Power Delivery communications.
Although plugs have 24 pins, cables have only 18 wires. In the following table, the "No." column shows the wire number.
| USB Type-C cable | Plug 2, USB Type-C | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Pin | Name | Wire color | No. | Name | Description | 2.0 | Pin | Name | |
| Shell | Shield | Braid | Braid | Shield | Cable external braid | Shell | Shield | ||
| A1, B12, B1, A12 | GND | Tin-plated | 1 | GND_PWRrt1 | Ground for power return | A1, B12, B1, A12 | GND | ||
| 16 | GND_PWRrt2 | ||||||||
| A4, B9, B4, A9 | VBUS | Red | 2 | PWR_VBUS1 | VBUS power | A4, B9, B4, A9 | VBUS | ||
| 17 | PWR_VBUS2 | ||||||||
| B5 | VCONN | Yellow | 18 | PWR_VCONN | VCONN power, for powered cables | B5 | VCONN | ||
| A5 | CC | Blue | 3 | CC | Configuration channel | A5 | CC | ||
| A6 | D+ | Green | 4 | UTP_Dp | Unshielded twisted pair, positive | A6 | D+ | ||
| A7 | D− | White | 5 | UTP_Dn | Unshielded twisted pair, negative | A7 | D− | ||
| A8 | SBU1 | Red | 14 | SBU_A | Sideband use A | B8 | SBU2 | ||
| B8 | SBU2 | Black | 15 | SBU_B | Sideband use B | A8 | SBU1 | ||
| A2 | SSTXp1 | Yellow | 6 | SDPp1 | Shielded differential pair #1, positive | B11 | SSRXp1 | ||
| A3 | SSTXn1 | Brown | 7 | SDPn1 | Shielded differential pair #1, negative | B10 | SSRXn1 | ||
| B11 | SSRXp1 | Green | 8 | SDPp2 | Shielded differential pair #2, positive | A2 | SSTXp1 | ||
| B10 | SSRXn1 | Orange | 9 | SDPn2 | Shielded differential pair #2, negative | A3 | SSTXn1 | ||
| B2 | SSTXp2 | White | 10 | SDPp3 | Shielded differential pair #3, positive | A11 | SSRXp2 | ||
| B3 | SSTXn2 | Black | 11 | SDPn3 | Shielded differential pair #3, negative | A10 | SSRXn2 | ||
| A11 | SSRXp2 | Red | 12 | SDPp4 | Shielded differential pair #4, positive | B2 | SSTXp2 | ||
| A10 | SSRXn2 | Blue | 13 | SDPn4 | Shielded differential pair #4, negative | B3 | SSTXn2 | ||
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.[31]
five system-defined Alternate Mode partner specifications exist. Additionally, vendors may support proprietary modes for use in dock solutions. Alternate Modes are optional; Type-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.[32]
| Thunderbolt Alternate Mode | Announced in June 2015 | USB-C is the native (and only) connector for Thunderbolt 3 and later Thunderbolt 3 (also carries 4× PCI Express 3.0, DisplayPort 1.2, DisplayPort 1.4, USB 3.1 Gen 2),[33] [34] [35] [36] Thunderbolt 4 (also carries 4× PCI Express 3.0, DisplayPort 2.0, USB4), Thunderbolt 5 (also carries 4× PCI Express 4.0, DisplayPort 2.1, USB4) | Current | ||
| DisplayPort Alternate Mode | Published in September 2014 | DisplayPort 1.2, DisplayPort 1.4,[37] [38] DisplayPort 2.0[39] | Current | ||
| Mobile High-Definition Link (MHL) Alternate Mode | Announced in November 2014[40] | MHL 1.0, 2.0, 3.0 and superMHL 1.0[41] [42] [43] [44] | Current | ||
| HDMI Alternate Mode | Announced in September 2016[45] | HDMI 1.4b[46] [47] [48] [49] | Not being updated | ||
| VirtualLink Alternate Mode | Announced in July 2018[50] | VirtualLink 1.0[51] | Abandoned |
Other protocols like Ethernet[52] have been proposed, although Thunderbolt 3 and later are also capable of 10 Gigabit Ethernet networking.[53]
All Thunderbolt 3 controllers support both Thunderbolt Alternate Mode and DisplayPort Alternate Mode.[54] 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.[55]
DisplayPort Alternate Mode 2.0: DisplayPort 2.0 can run directly over USB-C alongside USB4. DisplayPort 2.0 can support 8K resolution at 60 Hz with HDR10 color and can use up to 80 Gbps, which is double the amount available to USB data.[56]
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.
Alternate Mode hosts and peripheral devices can be connected with either regular Full-Featured Type-C cables, or with converter cables or adapters:
Active cables and adapters contain powered electronics to allow for longer cables or to perform protocol conversion. The adapters for video Alternate Modes may allow conversion from native video stream to other video interface standards (e.g., DisplayPort, HDMI, VGA or DVI).
Using Full-Featured Type-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.[59]
| Mode | USB 3.1 Type-C cable[60] | Adapter cable or adapter | Construction | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| USB[61] | DisplayPort | Thunderbolt | superMHL | HDMI | HDMI | DVI-D | Component video | ||||||
| 3.1 | 1.2 | 1.4 | 20 Gbit/s | 40 Gbit/s | 1.4b | 1.4b | 2.0b | Single-link | Dual-link | (YPbPr, VGA/DVI-A) | |||
| DisplayPort | Passive | ||||||||||||
| Active | |||||||||||||
| Thunderbolt | [62] | [63] | Passive | ||||||||||
| Active | |||||||||||||
| MHL | Passive | ||||||||||||
| Active | |||||||||||||
| HDMI | Passive | ||||||||||||
| Active | |||||||||||||
The diagrams below depict the pins of a USB-C receptacle in different use cases.
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, but it lacks the same physical connector so therefore USB-C is not backward compatible. V and GND provide 5V up to 500mA of current.
However, to connect a USB 2.0/1.1 device to a USB-C host, use of pull-down resistors Rd[64] on the CC pins is required, as the source (host) will not supply V until a connection is detected through the CC pins.
This means many USB-A–to–USB-C cables will only work in the A to C direction (connecting to a USB-C devices, e.g. for charging) as they do not include the termination resistors needed to work in the C to A direction (from a USB-C host). Adapters or cables from USB-C to a USB-A receptacle usually do work as they include the required termination resistor.
| GND | TX1+ | TX1− | V | CC1 | D+ | D− | SBU1 | V | RX2− | RX2+ | GND | |
| GND | RX1+ | RX1− | V | SBU2 | D− | D+ | CC2 | V | TX2− | TX2+ | GND |
The USB Power Delivery specification uses one of CC1 or CC2 pins for power negotiation between source device and sink device, up to 20 V at 5 A. It is transparent to any data transmission mode, and can therefore be used together with any of them as long as the CC pins are intact.
An extension to the specification has added 28 V, 36 V and 48 V to support up to 240 W of power for laptops, monitors, hard disks and other peripherals.[65]
| GND | TX1+ | TX1− | V | CC1 | D+ | D− | SBU1 | V | RX2− | RX2+ | GND | |
| GND | RX1+ | RX1− | V | SBU2 | D− | D+ | CC2 | V | TX2− | TX2+ | GND |
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, 10, or 20 Gbit/s (only by USB 3.2 x2 two-lane operations) signalling rates respectively. One of the CC pins is used to negotiate the mode.
V 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 at nominal either 1.5 A or 3 A is provided.[66] A third alternative is to establish a USB Power Delivery (USB-PD) contract.
In single-lane mode, only the differential pairs closest to the CC pin are used for data transmission. For dual-lane data transfers, all four differential pairs are in use.
The D+/D− link for USB 2.0/1.1 is typically not used when a 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 types of devices connected to it. Other devices may have the ability to fall back to 2.0, in case the 3.x connection fails. For this, it is important that SS and HS lanes are correctly aligned so that i.e. operating system messages indicating overcurrent conditions report the correct shared USB plug.
| GND | TX1+ | TX1− | V | CC1 | D+ | D− | SBU1 | V | RX2− | RX2+ | GND | |
| GND | RX1+ | RX1− | V | SBU2 | D− | D+ | CC2 | V | TX2− | TX2+ | GND |
In Alternate Modes 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.[38] 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.[38] [46] 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.[67]
| GND | TX1+ | TX1− | V | CC1 | D+ | D− | SBU1 | V | RX2− | RX2+ | GND | |
| GND | RX1+ | RX1− | V | SBU2 | D− | D+ | CC2 | V | TX2− | TX2+ | GND |
The external device test system (DTS) signals to the target system (TS) to enter debug accessory mode via CC1 and CC2 both being pulled down with an Rd resistor value or pulled up as Rp resistor value from the test plug (Rp and Rd defined in Type-C specification).
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 USB Power Delivery communication is to remain functional.
In this mode, all digital circuits are disconnected from the connector, and the 14 bold 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.
| GND | TX1+ | TX1− | V | CC1 | D+ | D− | SBU1 | V | RX2− | RX2+ | GND | |
| GND | RX1+ | RX1− | V | SBU2 | D− | D+ | CC2 | V | TX2− | 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 Rd resistor value or pulled up as Rp resistor value from the test plug:
| GND | TS1 | TS2 | V | CC1 | TS6 | TS7 | TS5 | V | TS4 | TS3 | GND | |
| GND | TS3 | TS4 | V | TS5 | TS7 | TS6 | CC2 | V | TS2 | TS1 | GND |
This mirroring of test signals will only provide 7 test signals for debug usage instead of 14, but with the benefit of minimizing extra parts count for orientation detection.
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.[68]
This mode also allows concurrent charging of a device exposing the analog audio interface (through V and GND), however only at 5 V and 500 mA, as CC pins are unavailable for any negotiation.
| GND | TX1+ | TX1− | V | CC1 | R | L | MIC | V | RX2− | RX2+ | GND | |
| GND | RX1+ | RX1− | V | AGND | L | R | CC2 | V | TX2− | TX2+ | GND |
| Tip | L | D− | |
| Ring 1 | R | D+ | |
| Ring 2 | Microphone/ground | SBU1 or SBU2 | |
| Sleeve | Microphone/ground | SBU2 or SBU1 | |
| DETECT1 | Plug presence detection switch | CC, VCONN | |
| DETECT2 | Plug presence detection switch | GND |
USB Type-C Authentication is an extension to the USB-C protocol which can add security to the protocol.[78] [79] [80]
An increasing number of motherboards, notebooks, tablet computers, smartphones, hard disk drives, USB hubs and other devices released from 2014 onwards include the USB-C receptacles. However, the initial adoption of USB-C was limited by the high cost of USB-C cables[81] and the wide use of Micro-USB chargers.
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. All Chromebooks with a USB-C port are required to support DisplayPort alternate mode in Google's hardware requirements for manufacturers.[82] 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.
It is also used on USB-C docks designed to connect a device to a power source, external display, USB hub, and optional extra (such as a network port) with a single cable. These functions are sometimes implemented directly into the display instead of a separate dock,[83] meaning a user connects their device to the display via USB-C with no other connections required.
Many cables claiming to support USB-C are actually not compliant to the standard. These cables can, potentially, damage a device.[84] [85] [86] There are reported cases of laptops being destroyed due to the use of non-compliant cables.[87]
Some non-compliant cables with a USB-C connector on one end and a legacy USB-A plug or Micro-B receptacle (receptacles also being invalid on cables) on the other end incorrectly terminate the Configuration Channel (CC) with a 10 kΩ pull-up to VBUS instead of the specification mandated 56 kΩ pull-up,[88] 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.[89] [90]
When a defective USB-C cable or power source is used, the voltage seen by a USB-C device can be different from the voltage expected by the device. This may result in an overvoltage on the VBUS pin. Also due to the fine pitch of the USB-C receptacle, the VBUS pin from the cable may contact with the CC pin of the USB-C receptacle resulting in a short-to-VBUS electrical issue due to the fact that the VBUS pin is rated up to 20 V while the CC pins are rated up to 5.5 V. To overcome these issues, USB Type-C port protection must be used between a USB-C connector and a USB-C Power Delivery controller.[91]
The USB-C port can be used to connect wired accessories such as headphones.
There are two modes of audio output from devices: digital and analog. There are primarily two types of USB-C audio adapters: active, e.g. those with digital-to-analog converters (DACs), and passive, without electronics.[92] [93]
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 and DACs that do not require special drivers,[94] and USB-C to 3.5 mm headphone jack adapters by Apple, Google, Essential, Razer, HTC, and Samsung.[95]
On the other hand, when a passive adapter is used, digital-to-analog conversion is done on the host device and analog audio is sent through the USB-C port. The sound quality is dependent on the phone's onboard DAC. Passive adapters are only compatible with devices that output analog audio, adhering to the Audio Adapter Accessory Mode specification.
| Specification | Devices | USB-C adapters | |||
|---|---|---|---|---|---|
| Active | Passive, without DACs | ||||
| Digital audio | Audio Device Class 3.0 (digital audio) | Apple iPhone 15, Google Pixel 2, HTC U11, Essential Phone, Razer Phone, Samsung Galaxy Note 10, Samsung Galaxy S10 Lite, Sharp Aquos S2, Asus ZenFone 3, Bluedio T4S, Lenovo Tab 4, GoPro, MacBook etc. | |||
| Analog audio | Apple iPhone 15, Moto Z/Z Force, Moto Z2/Z2 Force/Z2 Play, Moto Z3/Z3 Play, Sony Xperia XZ2, Huawei Mate 10 Pro, Huawei P20/P20 Pro, Honor Magic2, LeEco, Xiaomi phones, OnePlus 6T, OnePlus 7/7 Pro/7T/7T Pro, Oppo Find X/Oppo R17/R17 Pro, ZTE Nubia Z17/Z18 etc. | ||||
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.[96] 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.[97] Later in the year, Qualcomm released Quick Charge 4, which it claimed was – as an advancement over previous generations – "USB Type-C and USB PD compliant".[98]
In 2021, the European Commission proposed the use of USB-C as a universal charger.[99] [100] [101] On 4 October 2022, the European Parliament voted in favor of the new law, Radio Equipment Directive 2022/2380, with 602 votes in favor, 13 against and 8 abstentions.[102] The regulation requires that all new mobile phones, tablets, cameras, headphones, headsets, handheld video game consoles, portable speakers, e-readers, keyboards, mice, portable navigation systems, and earbuds sold in the European Union and supporting wired charging, would have to be equipped with a USB-C port and charge with a standard USB-C to USB-C cable by the end of 2024. Additionally, if these devices support fast charging, they must support USB Power Delivery. These regulations will extend to laptops by early 2026.[103] To comply with these regulations, Apple Inc. replaced its proprietary Lightning connector with USB-C beginning with the iPhone 15 and AirPods Pro second generation, released in 2023.[104]