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The wide range of transfer speeds available from a USB interface suits devices ranging from keyboards and mice up to streaming video interfaces. The USB3.0 standard does not directly specify a maximum cable length, requiring only that all cables meet an electrical specification: for copper cabling with AWG26 wires the maximum practical length is 3 meters (9ft 10in). [89] USB bridge cables [ edit ] USB Sleep-and-Charge Ports". toshiba.com. Archived from the original on 14 December 2014 . Retrieved 21 December 2014. a b "10 Power Rules", Universal Serial Bus Power Delivery Specification revision2.0, version1.2, USB Implementers Forum, 25 March 2016, archived from the original on 1 June 2012 , retrieved 9 April 2016 USB4 particularly supports the tunneling of the Thunderbolt 3 protocols, namely PCI Express (PCIe, load/store interface) and DisplayPort (display interface). USB4 also adds host-to-host interfaces. [2]
The USB interface defines protocols for recovery from common errors, improving reliability over previous interfaces. [12] a b Universal Serial Bus 3.0 Specification: Revision 1.0. June 6, 2011. p.531. Archived from the original on December 30, 2013 . Retrieved April 28, 2019. Connector properties [ edit ] Non-standard "USB extension cable", plug on the left, receptacle on the right. (USB does not allow extension cables. Non-standard cables may work but cannot be presumed reliable.) Note that this describes the power distribution model of USB that existed before Power-Delivery (USB-PD). Before PD, USB provided up to 7.5W through Type-A and Type-B connectors, and up to 15W through USB-C. All pre-PD USB power is provided at 5V. a b "USB 2.0 Specification Engineering Change Notice (ECN) #1: Mini-B connector" (PDF). October 20, 2000. Archived from the original (PDF) on April 12, 2015 . Retrieved April 28, 2019– via www.usb.org.In May 2021, the USB PD promoter group launched revision 3.1 of the specification. [58] Revision 3.1 adds Extended Power Range (EPR) mode which allows higher voltages of 28, 36, and 48 V, providing up to 240 W of power (48 V at 5 A), and the "Adjustable Voltage Supply" (AVS) protocol which allows specifying the voltage from a range of 15 to 48 V in 100 mV steps. [71] [72] Higher voltages require electronically marked EPR cables that support 5 A operation and incorporate mechanical improvements required by the USB Type-C standard rev. 2.1; existing power modes are retroactively renamed Standard Power Range (SPR). In October 2021 Apple introduced a 140 W (28 V 5 A) GaN USB PD charger with new Macbooks. [73] A bus-powered hub is a high-power device providing low-power ports. It draws 1 unit load for the hub controller and 1 unit load for each of at most 4 ports. The hub may also have some non-removable functions in place of ports. A self-powered hub is a device that provides high-power ports by supplementing the power supply from the host with its own external supply. Optionally, the hub controller may draw power for its operation as a low-power device, but all high-power ports must draw from the hub's self-power.
Since these currents are larger than in the original standard, the extra voltage drop in the cable reduces noise margins, causing problems with High Speed signaling. Battery Charging Specification 1.1 specifies that charging devices must dynamically limit bus power current draw during High Speed signaling; [51] 1.2 specifies that charging devices and ports must be designed to tolerate the higher ground voltage difference in High Speed signaling. Standard USB hub ports can provide from the typical 500mA/2.5W of current, only 100mA from non-hub ports. USB3.0 and USB On-The-Go supply 1.8A/9.0W (for dedicated battery charging, 1.5A/7.5W full bandwidth or 900mA/4.5W high bandwidth), while FireWire can in theory supply up to 60watts of power, although 10 to 20watts is more typical. Universal Serial Bus Revision 3.0 Specification, Sections 3.1.1.1 and 5.3.1.3". Usb.org. Archived from the original (ZIP) on 19 May 2014 . Retrieved 28 April 2019. The first Power Delivery specification defined six fixed power profiles for the power sources. PD-aware devices implement a flexible power management scheme by interfacing with the power source through a bidirectional data channel and requesting a certain level of electrical power, variable up to 5A and 20V depending on supported profile. The power configuration protocol can use BMC coding over the CC wire if one is present, or a 24MHz BFSK-coded transmission channel on the V BUS line. The USB Power Delivery specification revision3.0 defines an optional Programmable Power Supply (PPS) protocol that allows granular control over V BUS power, allowing a range of 3.3 to 21 V in 20mV steps to facilitate constant-current or constant-voltage charging. Revision 3.0 also adds extended configuration messages and fast role swap and deprecates the BFSK protocol. [57] [68] [69] The Certified USB Fast Charger logo for USB Type-C charging ports
The USB standard also provides multiple benefits for hardware manufacturers and software developers, specifically in the relative ease of implementation: Meeting the challenge of the universal charge standard in mobile phones". Planet Analog. Archived from the original on September 9, 2012 . Retrieved June 22, 2010. The three sizes of USB connectors are the default, or standard, format intended for desktop or portable equipment, the mini intended for mobile equipment, which was deprecated when it was replaced by the thinner micro size, all of which were deprecated in USB 3.2 in favor of Type-C. There are five speeds for USB data transfer: Low Speed, Full Speed, High Speed (from version 2.0 of the specification), SuperSpeed (from version 3.0), and SuperSpeed+ (from version 3.1). The modes have differing hardware and cabling requirements. USB devices have some choice of implemented modes, and USB version is not a reliable statement of implemented modes. Modes are identified by their names and icons, and the specification suggests that plugs and receptacles be color-coded (SuperSpeed is identified by blue).
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