USB is a serial bus standard for connecting computers and devices, which have been widely used in information communication products including personal computers, mobile devices, and much more.
This interface has a long history, with a constant evolution of standards, yet remains commonplace in technology communication standards. This article will give you a brief introduction to the development of the USB interface, the USB horizon, and the USB type C connector product line introduced by CUI Devices.
USB has become the main signal transmission technology today
USB is the abbreviation of Universal Serial Bus. The so-called "bus" is a circuit arrangement or communication system used to transfer data between components in the system. In this case, the "serial" bus transmits data one bit at a time over a single wire. However, USB connectors can transmit more than just data between components. It can also transmit electrical power and can accommodate many different hardware devices, from printers and keyboards to mobile phones and flash drives.
Before the development of USB protocol, computers used both serial and parallel ports to complete data transmission, and each device used various proprietary plugs, connectors, cables, expansion cards and necessary drivers. The data transmission rate was very slow; the running speed of parallel port is about 100 kB per second, and the running speed of serial port is 115-450 kb per second.
The USB 1.0 specification first appeared in early 1996. After a great deal of work by a consortium of companies, it initially transmitted data at a low speed of 1.5 Mbit per second and 12 Mbit per second at full speed. With the release of USB 2.0 at a speed of 480 Mbit per second in 2000 and USB 3.0 at a speed of 4.8 Gbps per second in 2008, the transmission speed has been further improved. After that, USB 3.2 has taken over the 3.1 and 3.0 standards, with a speed of up to 20 Gbps, which is the most commonly used standard at present. The latest version is USB4, released in 2019, with a transmission speed of up to 40 Gbps, and it is gradually being introduced into various devices.
For many years, USB standards have been guided and certified by the USB Implementers Forum (USB-IF) organization, and the forum has more than 700 member companies. Over the years, the work of USB-IF has led to the release of a series of standards, and the transmission speed of specifications is getting faster and faster. Speed and video resolution are improved through a small and inexpensive USB interface, which makes USB connector the dominant signal transmission technology used in the world today.
Diversified USB physical form factors to meet different needs
There are many types or physical specifications of USB connectors that can be used in various applications, including:
- Type A: The most original and common USB connector, also known as the USB standard A, which is used to connect downstream peripheral devices to host devices. The flat rectangular shape is held in place by friction for easy insertion and removal. It provides a 5 V DC power supply on one of the pins and is compatible with all types of USB protocols.
- Type B: The Type B connector is most commonly used to connect with USB computer peripherals devices. This connector is square with slightly beveled corners on the top. Like Type A, it is held in place by friction. It was developed to allow peripheral devices to be connected without the risk of connecting two host computers to each other. This type of connector is still in use, but micro versions are more common.
- USB Type C: This is the newest USB interface, with reversible symmetry design, which can be plugged in from either side up, and any USB-C device can be plugged in from either end of the cable. It can transmit USB 3.2 (formerly 3.1 and 3.0), 2.0 and 1.1 signals, and can transmit data at a speed of up to 20 Gbps, with either directional power delivery of up to 100 W (which can be extended to 240 W through USB PD 3.1), and can support DisplayPort video and four-channel audio. Type C also supports USB4 and Thunderbolt, which is a hardware interface that allows peripheral devices to be connected to a computer with a data transmission speed of up to 40 Gbps.
- Micro and Mini A and B: These are small versions of Type A and Type B connectors, which provide physically smaller connections while maintaining high-speed transmission rate of 480 Mbps and On-The-Go (OTG) function, allowing mobile devices and other peripheral devices to act as USB hosts.
- Type AB: This connector allows Micro A and Micro B plugs to connect to this single receptacle type, which provides greater flexibility.
Various types of USB connectors can only mate with their associated male or female connectors with no cross compatibility. Although the connectors themselves are standard, their enclosures can be significantly changed according to different applications, which leads to the development of IP rated (ingress protection) USB connectors, providing robust protection against solid or liquid intrusion into devices used in harsh environments.
Most USB cable assemblies also have one type of connector at one end and different types of connectors at the other end. Type A to Type B or Type C are very common. Because Type C is specially designed to be interchangeable, Type C is more common at both ends of the cable, and its usage is gradually increasing with the wider adoption of Type C ports. The USB 3.0 Micro B plug has a wider connection to adapt to a higher data transmission rate, but it cannot be used with the USB 2.0 Micro B socket. However, devices with USB 3.0 Micro B ports can be mated with older USB 2.0 Micro B male plugs.
When incorporating USB connectors into a design, it is also important to note that some regions are introducing regulations that require new electronic devices to utilize USB Type C connectors for charging cables. For example, the European Union has announced that chargers for mobile devices must be based on USB Type C in 2024, with laptops to soon follow in 2026. This means that all mobile devices sold in the EU will use the same type of charger, benefiting the environment and frustrated consumers.
Continuous evolution of faster USB communication standards
The USB communication standard defines the data transmission speed, handshake protocols, and power supply specification between the devices used. Over the years, the standard has been greatly improved. The data transmission speed ranges from USB 1.0 with a speed of 1.5 Mbit per second to USB 3.2 with a speed of 20 Gbps, and now to USB4 with a speed of 40 Gbps. Each succeeding version promotes a new round of interconnect hardware.
The USB communication standard is confusing because of frequent retrospective naming changes, but at present, USB 3.2 is the most accessible USB standard, which is compatible with Type A and Type C connectors, although it can range from 5 Gbps to 20 Gbps. However, as in many installations, different versions are often used in the same system. If devices using the newer USB version and the older version are communicating, they will default to the older version and speed. This is the function of software, but compatibility with standards is also related to hardware.
All Type C connectors are compatible with USB 3.2, but some Type C connectors still conform to earlier standards. Type A and Type B depend on the cable, and different connector colors usually indicate different versions for quick reference. Confusion often occurs when looking at the relationship between physical connector standards and communication standards.
According to the original standard, USB connection requires a host. Type A connectors are usually represented as host devices, while Type B is usually connected to peripheral devices. There is no such requirement when using USB OTG (On The GO). USB OTG is a specification that allows USB devices (such as smart phones) to act as hosts and connect to other USB devices. Basically, it allows USB devices to read data from other devices without a computer.
The progression of USB power delivery specifications
The USB standard was originally a data interface protocol to simplify the interconnectivity between devices and provide some power. Nowadays, it has developed from a data interface providing limited power to an important power conduit including data interface, and many devices can now charge or receive power through USB connection.
Many manufacturers made concerted efforts to standardize power transmission and added a feature set in the form of USB Power Delivery (USB PD) standard. When using Type C, USB PD can provide a variable voltage of up to 20 V and a maximum current of up to 5 A, with a total power transmission limit of up to 100 W. The USB PD 3.1 standard released in 2021 has extended the power transmission capacity to 240 W. In addition, the power direction is no longer fixed, which can not only supply power from the host or peripherals, but also optimize power management across multiple peripherals.
USB PD needs digital devices to handshake to reach these higher ratings. If it lacks the necessary chips and can't handshake, the system will return to the 5 V/1 A standard. This has nothing to do with the USB version and type, but the type is needed to support the USB PD standard. For example, a Type A to Type C cable supporting version 2.0 and later can use the PD function.
PD can also be used with devices that do not transmit data, and it is powered by USB only. It does need separate communication lines for power negotiation, so the design and manufacture are slightly more complicated than many non-USB formats. The fact that PD has created a charging standard across a large array of devices and simplified and consolidating chargers can offset this complexity and reduce the inconvenience of e-waste and the need for multiple cables for different devices.
USB applications are constantly expanding to various electronic devices
By providing small form factor, easy design and use, high communication speed and enhanced power transmission, USB connectors can be used in a very wide and growing range of applications, such as desktop and laptops computers, disk drives, printers, scanners, Joysticks and controllers, video cameras, mobile phones, smart TVs, game consoles and so on. For some devices that don't need data transmission, USB connectors can also be used solely to supply power for rechargeable flashlights, charging pads and many other portable consumer devices.
The robustness and speed of the latest USB standard have also opened up more applications. It now has bandwidth, reliability and power delivery capability, and can be used in industrial applications such as data acquisition and monitoring, machine vision and process control. Basically, any application that uses 240 W or less power can be powered by USB power supply.
CUI Devices has introduced many USB connector lines, including Type A, Type B, Micro AB, Micro B, Mini AB, Mini B and Type C USB connector types that meet various USB standards, including 2.0, 3.2 Gen 1 (formerly USB 3.1 Gen 1), 3.2 Gen 2 (formerly USB 3.1 Gen 2), 3.2 Gen 2x2 (formerly USB 3.2) and USB4 40 Gbps. With a data transmission speed of up to 40 Gbps and a power delivery of up to 240 W, these USB connectors can be used in almost any design. You can purchase related products directly from the website of Arrow Electronics: Purchase Here
Conclusion
USB is a very flexible standard, which is almost universally adopted in the fields that need data transmission and power supply. USB connectors and cable assemblies combine ease of use and intelligent technical specifications, enabling product or system designers to reduce cabling requirements, clutter, and footprint, ensure backward compatibility, and cut overall costs. Whether designing for the future or connecting traditional products, understanding the functions of USB will help designers create products that can be used by practically everyone.