What is a USB Cable?
2024-09-02USB Related Standards
2024-09-03Ubiquitous to modern society, USB tech can be found in at least one or more devices people use on a daily basis. However, USB cables come in a variety of connections, most of which are incompatible with the others. This makes replacing a USB cable a troublesome task, especially when the differences between each may seem trivial to the inexperienced.
For instance, while micro B and mini USBs may use synonymous terms, you cannot simply use one plug to connect to the other’s port. To make matters even more confusing, the USB tech industry is constantly evolving that even the same plug type can differ between each version of USB, simultaneously influencing the plug’s performance.
We have put together this exhaustive guide to help you untangle all the nuanced idiosyncrasies between the different types of USB cables on the market.
USB Type A
Also known as USB standard A connector, the USB A connector is primarily be used on host controllers in computers and hubs. USB-A socket is designed to provide a “downstream” connection intended for host controllers and hubs, rarely implemented as an “upstream” connector on a peripheral device. This is because USB host will supply a 5V DC power on the VBUS pin. As such, it is important to remember while purchasing USB cables it is safest to make sure at least one of the plugs is a USB A.
Though not that common, USB A male to A male cables are used by some implementers to make connections between two USB A style female port. Be aware that typical A-A cables are not intended for connection between two host computers or computer to hub.
USB Type B
Also known as USB standard B connector, the B style connector is designed for USB peripherals, such as printer, upstream port on hub, or other larger peripheral devices. The primary reason for the development of USB B connectors were to allow the connection of peripheral devices without running the risk of connecting two host computers to one another. USB B type connector is still used today, though it is slowly being phased out in favor of more refined usb connector types.
USB Type C
USB-C or USB Type-C connector is the newest USB interface came to the market along with the new USB 3.1 standard. Different from previously mentioned USB A type and B type connector, USB C Type connector can be used on both host controller ports and devices which use upstream sockets. In the last few years a numbers of laptops and cellphones have appeared on the market with C style USB connectors.
USB Type C connector is compatible with USB 2.0, 3.0, 3.1 Gen 1 and Gen 2 signals. A full feature USB 3.1 Gen 2 C to C cable is able to transmit data at maximum 10 Gbps with enhanced power delivery of up to 20V, 5A (100W) and to support DisplayPort and HDMI alternate mode to transfer video and audio signal.
USB Mini B
Similar to USB B type connector, USB mini B sockets are used on USB peripheral devices, but in a smaller form factor. The mini B plug by default has 5 pins, including an extra ID pin to support USB On-The-Go (OTG), which allows mobile devices and other peripherals to act as a USB host.Initially, this plug was designed for earlier models of smartphones, but as smartphones have become more compact and with sleeker profiles, the Mini USB plug has been replaced by the micro USB. Now, the Mini-B is designed for some digital cameras while the rest of the mini plugs series have become more of a legacy connectors as they are no longer certified for new products.
USB Micro B
The micro USB B connector essentially a scaled down form of the mini USB which allowed mobile devices to get slimmer while still maintaining the ability to connect to computers and other hubs.
The micro B type connector holds 5 pins to support USB OTG, which permits smartphones and other similar mobile devices to read external drives, digital cameras, or other peripherals as a computer might. Note that to enable OTG feature, special wiring connection needs to be implemented in the cable assembly.
On Oct. 22, 2009, the international Telecommunication Union (ITU) announced to include Micro-USB interface into the Universal Charging Solution (UCS) that has been adopted broadly by industry.
USB 3.0 Type A
Inheriting the same design to the A-Type connector used in USB 2.0 & USB 1.1 application, USB 3.0 A is also provides a “downstream” connection that is designed for use only on host controllers and hubs.
However, USB 3.0 Type A processes additional pins that are not in the USB 2.0 A Type. USB 3.0 connector is designed to support 5Gbps bandwidth “SuperSpeed” data transfer, whereas, lower data rate can be transmitted with backward compatibility to USB 2.0 ports. USB 3.0 connectors are often in blue color or with “SS” logo to help distinguish them from previous generations.
USB TYPE AND USB VERSION—WHAT’S THE DIFFERENCE?
|
TYPE |
VERSION |
|
The shape of the USB connector or port Examples: USB Type-C, USB Type-B Micro |
The technology that allows data to be transferred along a cable from one device to another Examples: USB 2.0, USB 3.0 |
USB TYPES EXPLAINED
The term “USB type” can mean three different things:
- The connectors at the end of a USB cable
- The ports the cable is plugging into
- The cable itself (and sometimes this will have two types in its name)
In the case of 1 and 2, the type describes the physical shape of the connectors or ports.
This cable would plug into two ports that have these shapes:
Although a cable has two differently shaped connectors, it takes the name of whichever connector is not USB Type-A. That’s because USB Type-A is the most commonly used USB port and connector so an alternative type is the most distinguishing feature.For example, this cable would be considered a USB Type-C cable.
TYPES OF USB CABLE
USB cables are named in one of two ways:
1. AS A SINGLE TYPE
For example, a USB Type-C cable.
With these cables, the type is whichever end of the cable isn’t the standard USB Type-A connector. So, for example, a cable with both a USB Type-A and a Type-C connector is a USB Type-C cable.
If both connectors are USB Type-A, it would be a USB Type-A cable (or a USB male to male cable or, simply, a USB cable).
An iPhone cable is described as an Apple Lightning cable, to correspond with the iPhone’s unique Lightning connector.
An Android cable is called a Micro-USB cable.
2. AS ONE TYPE TO ANOTHER
For example, a USB Type-A to USB Type-C cable.
If the cable has a Type-A connector at one end (as in the above image), that will usually be the first type. The second will be the shape of connector that will plug into your device.
Some cables have the same connector at both ends and are named accordingly—for example, a USB Type-C to USB Type-C cable.
TYPES OF USB PORT
The port (also called a socket, jack or receptacle) is the part of your device the USB connector plugs into. USB ports are sometimes referred to as “female”, as they accept a “male” connector.
The following are the most commonly used port types:
USB 2.0
USB 3.0
USB-C Lanes and Speeds
To understand USB data transfer rates, you need to know a little about the design of the USB-C connector. A USB Type-C connector has four pairs of pins known as “lanes” that transmit (TX) and receive (RX) data (see highlighted pins in Figure 1 below). USB 3.0 (5 Gbps) and USB 3.1 (10 Gbps) use one TX lane and one RX lane, depending on the orientation of the connector. USB 3.2 takes advantage of all four lanes to achieve a 20 Gbps data rate.
Figure 1: USB-C Connector Pinouts
The naming convention recently adopted for USB 3.2 incorporates speed x lanes. For example, USB 3.2 Gen 1×2 means 5 Gbps x 2 lanes, for a connection speed of 10 Gbps.
Specification | Signaling Rate/Lane | Number of Lanes | Aggregate Bandwidth |
USB 3.2 Gen 1×1 | 5 Gbps (SuperSpeed) | 1 | 5 Gbps |
USB 3.2 Gen 2×1 | 10 Gbps (SuperSpeed+) | 1 | 10 Gbps |
USB 3.2 Gen 1×2 | 5 Gbps (SuperSpeed) | 2 | 10 Gbps |
USB 3.2 Gen 2×2 | 10 Gbps (SuperSpeed+) | 2 | 20 Gbps |
The USB4 Gen 2×2 specification (known by its marketing name, USB4 20Gbps) and USB 3.2 Gen 2×2 both offer 20 Gbps connection. USB4 Gen 3×2 (USB4 40Gbps) uses a different data encoding scheme to achieve 20 Gbps per lane and 40 Gbps when in dual lane mode.
Specification | Signaling Rate/Lane | Number of Lanes | Aggregate Bandwidth |
USB4 Gen 2×2 | 10 Gbps | 2 | 20 Gbps |
USB4 Gen 3×2 | 20 Gbps | 2 | 40 Gbps |
What’s New in USB4?
USB 4 (officially “USB4” without the space) is an important update, not only for the new capabilities it offers but because it helps to resolve the confusion over USB 3.x naming and, for the most part, it gives users a predictable and consistent experience. The USB4 protocol requires a USB-C to USB-C cable.
Up to 40Gbps Data Transfer Rate: USB4 devices are required to support 20 Gbps (2.4 GB/sec). They can optionally support 40 Gbps (4.8 GB/sec) if they use the shorter 0.8 meter Gen 3 cable.
Multiple Data and Display Protocols: USB4 supports USB 3.2, PCIe and DisplayPort 1.4a through a technique called protocol tunneling. DisplayPort and Thunderbolt 3 are also supported via Alt Mode.
Backward compatibility with USB 3.2, USB 2.0 and Thunderbolt 3: USB4 maintains compatibility with previous versions of the USB specification and, thanks to its Thunderbolt 3 foundation, supports TB3 Alt Mode too.
Video and Data Bandwidth Optimization: USB 3.2 allocated fixed bandwidth to data or video or, in DP Alt Mode, gave 100% to video. USB4 dynamically allocates bandwidth to video and data based on actual needs.
100 Watt Charging: All USB4 devices support USB Power Delivery. When a device is connected to a USB4 port, USB PD negotiates a “contract” to deliver power, safely supplying up to 100 W (5A/20V).
What is Protocol Tunneling?
When devices talk to one another, they do so using a protocol. If both devices can speak and understand the same protocol, a connection can be established. Conceptually, Protocol Tunneling creates a “pipe” with one protocol and uses it to send data in another protocol. USB4 Protocol Tunneling creates a USB-C tunnel through which DisplayPort or PCIe data can be sent. USB4 Protocol Tunneling is similar to Alt Mode but doesn’t require a DP or PCIe controller.
What is USB4 Fabric?
The word fabric is a metaphor used to describe a network of interconnecting nodes, such as switches. When illustrated, the crisscross pattern resembles woven cloth. The term has been adopted by the USB Implementers Forum (USB-IF) to describe how USB4’s tunneling architecture dynamically manages the connection between USB4 routers so multiple protocols can simultaneously share the fabric’s resources.
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USB Standards
Your USB connections are about to become faster! Products compatible with the Thunderbolt™ 3 standard have entered the market. This latest generation offers both power delivery and bidirectional data transfer at speeds up to 4x faster than USB 3.2 Gen 2, and can create never-before-possible computing options for personal devices.
Chart 1: USB Cable Types, Standards and Speeds
Standard | Also Known As | Logo | Year Introduced | Connector Types | Max. Data Transfer Speed | Cable Length** |
USB 1.1 | Full Speed USB | 1998 | USB-A USB-B | 12 Mbps | 3 m | |
Hi-Speed USB | 2000 | USB-A USB-B USB Micro A USB Micro B USB Mini A USB Mini B USB-C* | 480 Mbps | 5 m | ||
USB 3.0 USB 3.1 Gen 1 SuperSpeed | 2008 (USB 3.0) 2013 (USB 3.1) | USB-A USB-B USB Micro B USB-C* | 5 Gbps | 3 m | ||
USB 3.1 USB 3.1 Gen 2 SuperSpeed+ SuperSpeed 10Gbps | 2013 (USB 3.1) | USB-A USB-B USB Micro B USB-C* | 10 Gbps | 3 m | ||
USB 3.2 Gen 2×2 | USB 3.2 SuperSpeed 20Gbps | 2017 (USB 3.2) | USB-C* | 20 Gbps | 3 m | |
USB 4 | USB4 Gen 2×2 USB4 20Gbps | 2019 | USB-C* | 20 Gbps | 0.8 m | |
USB 4 | USB4 Gen 3×2 USB4 40Gbps | 2019 | USB-C* | 40 Gbps | 0.8 m |
* USB-C is more accurately known as Type C or USB Type C
** Cable length is the length covered by the specification. Longer lengths can be achieved using active cables and in some cases, longer passive cables
Does USB-C support USB 2.0?
It can but first let’s clarify the difference between USB-C and USB. USB-C is a physical connector and, despite the name, it does not imply support for any particular version of the USB standard. In fact, a USB-C connector can be used to connect peripherals using other interface standards such as Thunderbolt 3.
When buying USB-C cables, make sure to check the charging wattage and USB data rate supported. A charging cable supporting USB 2.0 can be longer than USB 3.x and USB4 cables but is limited to a 480 Mbps data transfer rate and will not support alt-modes.
