USB4

USB4

Type	USB
Production history
Designer	USB Promoter Group
Designed	29 August 2019; 5 years ago (2019-08-29)
Superseded	USB 3.2
General specifications
Daisy chain	No
Audio signal	DisplayPort
Video signal	DisplayPort
Pins	24
Connector	USB-C
Electrical
Max. voltage	48 V (PD 3.1)
Max. current	5 A (PD)
Data
Data signal	USB or PCIe
Bitrate	20 Gbit/s 40 Gbit/s 80 Gbit/s 120/40 Gbit/s asymmetric

Universal Serial Bus 4 (USB4), sometimes erroneously referred to as USB 4.0, is the most recent technical specification of the USB (Universal Serial Bus) data communication standard. The USB Implementers Forum originally announced USB4 in 2019.

USB4 enables multiple devices to dynamically share a single high-speed data link. USB4 devices must support a signaling rate of at least 20 Gbit/s. The current version allows signalling rates of 40 Gbit/s (since USB4, first version) and 80 Gbit/s (since USB4 version 2.0).^[1][2] USB4 is only defined for USB-C connectors and its Type-C specification^[3] regulates the connector, cables and also power delivery features across all uses of USB-C cables, in part^[4] with the USB Power Delivery specification.^[5]

The USB4 standard mandates functionally backwards compatibility to USB 3.2 (which supersedes USB 3.0 and USB 3.1) and dedicated backward compatibility with USB 2.0 (and therefore subsequently USB 2.0/1.1).^[6] The dynamic sharing of bandwidth of a USB4 connection is achieved by tunneling of other protocols. This includes tunneling of USB 3.2 Gen 2 and DisplayPort. Other optional protocols, such as PCI Express and Ethernet can also be tunneled.

USB4 is based on the Thunderbolt 3 protocol; however, the implementation of Thunderbolt 3 protocol is mandatory only for hubs.^[7]