by Mouser Electronics
USB Type-C™, the newest USB connector standard, is about cabling. You’ll begin to see the small, reversible Type-C connectors on devices from laptops and smart phones to flash drives and video systems. The list is inclusive and growing because the Type-C cable can provide both data and power to hosts and devices, as well as offer a universal power cable solution. Smaller than the standard USB connectors, the rugged connector can be used in slimmer designs and be configured for a variety of applications. Its promise: that tangle of power adapters and proprietary cables you have clumped around your AC outlet fades away and your data transfers quickly. Unique video cables are a thing of the past.
Type-C is also the realization of a vision to bring various parts of the USB specifications together to form a complete system of cabling, power, and signal management for all applications. USB 2.0 Type-C cables support USB 2.0 Low-speed, Full-Speed and High-speed formats. USB Type-C full-featured cables also support the SuperSpeed+ and SuperSpeed 10G data rates of USB 3.1 Gen1 and Gen2. The Type-C interconnect uses USB Power Delivery (PD) to enable the 100W power capability that allows faster battery charging and the ability to power larger devices such as laptops, monitors and TVs. Type-C full-featured cables are active, electronically marked cablesiincorporating signal conditioning, power management, and configurable connections. Wires within these cables can be reconfigured via PD vendor defined messages (VDMs) to handle video and audio signals using alternate and accessory modes. With its smaller size, range of power levels, faster data rates and the ability to handle multiple data protocols, Type-C positions itself as the USB connector of the future.
Type-C connectors are easier to use; you don’t have to check plugs for the right side or correct orientation. Both sides of a Type-C cable have the same connector and it can be plugged into a receptacle either side up. Identifying the host as the downward facing port (DFP) and device as the upward facing port (UFP) is done electronically using the interconnect signals.
The Type-C connector was designed to enhance smaller device design and is physically smaller than previous USB connectors; openings are approximately 8.4mm by 2.6mm. This connector has come a long way from its ancestor with four wires. As illustrated inAmphenol’s new Type-C connectors, there are 24 connections, with the pin sets arranged in two rows, 12 connections on each side (A1-A12; B12-B1). The physical symmetry allows the connector to be “flippable.” Receptacle and plug pin assignments are given in the Table 1 and 2, respectively. Type-C receptacles are rated for 5 Amps. Type-C signal handling is backwards compatible; the four wires for USB 2.0 signals are included (+5 Vbus, Ground and differential data signals DP+ and DP-). Also included are the differential transmit and receive pairs required for SuperSpeed+ and SuperSpeed 10G signals. There are additional wires to handle Type-C configuration and alternate and accessory modes.
Table 1. Type C Receptacle Pin Connections (front view)
Table 2. Type C Full Featured Plug Pin Connections (front view)
With USB-C intended to be used for many devices, the connector is spec’d to be rugged. TE Connectivity’s USB Type-C connectorsprovide EMI design on the back of the receptacle shell, enhanced performance over similar legacy products, and additional board retention features to provide enhanced performance in harsh environments.
The versatility offered by USB-C is realized through configurable cables, ports and power settings. Type-C connections allow additional capability, but require more complex management. As with previous USB connectors, incorporating controllers into existing chips and using FPGA technology enables the sleek packaging Type-C was developed for. Port controllers work with PD controllers to negotiate power requirements and direction. VDM commands control entry and exit from alternate and accessory modes. The Cypress Semiconductor controller uses the ARM Cortex-M0 microcontroller and is optimized for low power.
Fairchild offers a programmable thin-client solution controller with an integrated Vconn switch. The FUSB300C programmable USB Type-C controller supports all roles and alternate/accessory modes. Type-C connectors electronically detect and configure connections using the Configuration Channel (CC). Using biphase mark coding (BMC) to communicate over the CC, the cable is configured for bus routing, power management, alternate and accessory modes. Controller logic supports:
- Detecting valid cable connections attached to a port. With Type-C connectors at both ends of a cable, host-to-host and device-to-device connections are physically possible but not supported. Valid connections are detected and acted upon; if two hosts or two devices are connected, nothing will happen.
- Resolving data bus routing. The orientation of the cable and signaling requirements are detected from receptacle and plug connections. Routing is configured for correct communication regardless of plug orientation.
- Resolving host/device roles. Type-C ports can be host-only, device-only or dual-role ports. The host-only and device-only ports function in the traditional USB host and device roles; the host being the downward facing port (DFP) and the device the upward facing port (UFP). Type-C identifies these roles electronically, instead of having functionally shaped connectors. Also, the dual-role ports can be reconfigured: a laptop may function as an UFP when being charged by a monitor or a DFP when powering a mini-fan.
- Determining if the Vbus is using Type-C standard power or PD.
- Configuring Vconn if needed.
- Supporting optional alternate and accessory modes.
Previous configuration communications were accomplished using binary frequency shift keying (BFSK) directly on the Vbus. For backwards compatibility, Type-C controllers can also use BFSK on the Vbus, but not concurrently with BMC on the CC. Type-C hubs can be used to increase DFP capabilities. They have one UFD port, which must be clearly marked and one or more DFPs. The UFP cannot be a dual-role port and alternate/accessory modes are not handled by hubs.
Alternate and accessory modes
Alternate and accessory modes enable Type-C cables to handle non-USB data protocols. To support these different protocols, certain wires in the cable are used differently than when handling USB communications. The wires that can be re-purposed are the four SuperSpeed wire pairs (SSTX1, SSTX2, SSRX1 and SSRX2), the two side band wires (SBU1, SBU2), the two 2.0 data lines (DP+, DP-), Vconn, and a CC wire. Depending on the mode, not all of these wires are reconfigured. The alternate and accessory modes are set up using PD VDM commands received via the CC. VDMs will direct the controller to enter a mode and continue to communicate in that mode until a VDM exit command is received.
Reconfiguring the cable signal wires allow video signals used in DisplayPort, VGA, HDTV and HDMI to be transported over the cable. Alternate mode operation is also required for certain power connections. Devices requiring direct connections, like docking stations, captive cables and thumb drives reassign the Vconn line and require being set up in alternate mode.
The audio adapter accessory mode enables Type-C support for analog audio headsets. In this mode, the audio signal is multiplexed the onto the connector pins. Since the audio signals are the same as those used in 3.5mm audio jacks, a 3.5mm to Type-C adapter can be used.
Type-C cables are constructed with Type-C connectors on each end. They support USB 2.0 and USB 3.1 features and data speeds; they can implement PD. The practical length for Type-C standard cable assemblies are given in Table 3, along with requirements for electronically marked cables. Cables implementing PD and full featured Type-C cables must be electronically marked. Up to 1W is drawn from Vconn (or other source) to support electronically marked cables.
Table 3. Type-C Cable Lengths
|USB 2.0||< 4m||Standard 3 Amp, optional; PD 5 Amp, Required|
|USB 3.1 Gen1||< 2m||Required for 3 Amp and 5 Amp|
|USB 3.1 Gen2||< 1m||Required for 3 Amp and 5 Amp|
Although Type-C connectors include all the signal wires necessary to support USB 2.0 and USB 3.1 signals, their physically different shape require adapter cables if used with legacy connectors.
Legacy adapter cables connect Type-C connectors to:
- USB 2.0 and USB 3.1 Type A connectors
- USB 2.0 Type B mini and micro connectors
- USB 3.1 Type B mini and micro connectors
Captive cables, which have a Type-C connector at one end, with the other end attached to a vendor-specific device, are allowed and must follow Type-C signaling requirements. The vendor cable may be hardwired or have a vendor-specific disconnect protocol. Captive cables can be full-featured or support USB 2.0.
The USB Type-C connector is smaller and more rugged than previous USB connectors. Type-C cables, with controller support, handle data speeds up to 10Gbps, deliver 100W of power and can be configured to carry USB, video, and audio signals and promise a one cable solution for future designs. For more information about USB, visit Mouser Electronics’ USB Technology site.
Note: USB Type-C™ and USB-C™ are trademarks of USB Implementers Forum.