Brief Introduction to USB4™

What’s with the New Name

With the latest version of the USB specification, the abbreviated name no longer includes a space between “USB” and the number indicating the version. Also, there is no longer a decimal point to indicate small progressions in the specification, as was the case with USB 3.1 and USB 3.2. This new naming scheme should help to reduce confusion for consumers.

What’s New from an End User Perspective

USB4 introduces the ability to dynamically control bandwidth allocation between various protocols, as well as doubling the maximum available bandwidth.
USB4 introduces the idea of tunneling, which allows multiple protocols to be combined over a single interface to increase flexibility. USB 3.2 data, display (DisplayPort) and load/store (PCIe) information tunneling is possible depending on the device. It also allows devices to intelligently allocate the total available bandwidth based on the requirements of the devices which are connected. This helps to improve efficiency by avoiding a predetermined amount of bandwidth being reserved for a device that may not need it. If this sounds familiar, it is because protocol tunneling concept has been applied to USB4.
USB4 also support native USB 3.2 and DP Alt Mode.

Protocol Tunneling Support
  USB 3.2 DisplayPort PCIe
USB4 Host (Computer) optional
USB4 Device (Peripheral) optional optional optional
USB4 Hub/Dock

There are two speed levels defined in the USB4 specification, USB4 20Gbps and USB4 40Gbps. In some cases, these may be inadvertently denoted as Gen2x2 and Gen3x2 respectively, however the correct marketing terminology only indicates the data rate to reduce confusion amongst consumers. Similar to USB 3.2, both available SuperSpeed lanes in a USB Type-C® connector are combined into a single dual-lane interface to achieve these higher data rates.

New Brand Name
Revision New Brand Name Data Rate
USB 3.2 Gen 1x1 SuperSpeed USB 5Gbps 5Gbps
USB 3.2 Gen 2x1 SuperSpeed USB 10Gbps 10Gbps
USB 3.2 Gen 2x2 SuperSpeed USB 20Gbps 20Gbps
USB4 Gen 2x2 USB4 20Gbps 20Gbps
USB4 Gen 3x2 USB4 40Gbps 40Gbps

Single and Dual-Lane Comparison

What’s New with Connectors and Cables

The same USB Type-C form factor is carried over to ensure backwards compatibility. However, there are new signal integrity requirements for USB4 which will push vendors to develop new and improved connectors and cables.
For the first time, there are normative, or mandatory, signal integrity requirements for individual plug and receptacle connectors which plan to be certified for use in UBS4 40Gbps devices. Cable assemblies have always required signal integrity testing, but connector signal integrity was previously evaluated as part of a complete device such as a computer, cable assembly, or docking station.
Although the connectors make up a relatively short portion of the entire USB signal path when compared to PCB traces and cables, it can be a major source of unwanted signal reflection and crosstalk. Proper connector design and precision manufacturing are essential to make sure connectors are not a bottleneck for the complete USB channel.
Cable assembly requirements for USB4 40Gbps certification are much stricter than previous versions which will reduce the maximum length possible for passive cable assemblies to 0.8m. However, there are ongoing developments for active cable assemblies which will allow longer cable lengths with built in equalization and amplification functions.

JAE’s Involvement

As a global leader in interconnect technology, JAE was an active contributor in the USB-IF working group tasked with creating the new specifications. JAE will develop and manufacture connectors and cables which meet these latest specifications to support the next generation of advanced electronic computing devices.
For more information on JAE connector and cable options, please contact us.

USB4™, USB Type-C®, USB-C® are trademarks of USB Implementers Forum.

Company Name Japan Aviation Electronics Industry, Limited
Establishment of Business August 20, 1953
Capital ¥10.69 billion
President (Representative Director) Tsutomu Onohara
Head Office 21-1, Dogenzaka 1-chome, Shibuya-ku, Tokyo 150-0043, Japan
TEL +81-3-3780-2711
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URL https://www.jae.com/