Differences Between Usb Speeds And Connectors

By Author: Sabrina Moran
Total Articles: 4
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The Universal Serial Bus (USB) has become an indispensable cross-platform connector for many consumer electronics, most of which users rely on daily, such as computers, smart phones, global positioning systems (GPS) and digital cameras. Since the start of its development in the mid-1990s, it has evolved into many forms that discerning consumers should be aware of, particularly with regards to its speed specification and connector types.

The original USB 1.0 specification (Full Speed) was released in 1996 as a result of a development by several companies to standardize connecting external devices to PCs at greater data rates. It has two specified data rates of 1.5 Mbps (Low-Bandwidth) and 12 Mbps (Full-Bandwidth). However, it was not widely adopted until the release of the USB 1.1 in 1998, which resolved issues related to hubs that were identified in USB 1.0.

In 2000, the USB 2.0 specification, also known as “High Speed,” was released with a higher maximum signal rate of 480 Mbps and an effective throughput ranging from 35 to 40 MBps (280 to 320 Mbps). The increased bandwidth allowed the market segment for ...
... USB peripherals to grow, such as with high density storage devices, high performance video-conferencing cameras, higher resolution printers and scanners, etc.

The second major revision, USB 3.0 (Super Speed), was released in 2008, with a transfer rate of 5 Gbps – ten times the rate of the USB 2.0. A bi-directional datapath increases the bandwidth by eliminating the one-way communication of previous iterations. All USB 3.0 interfaces are blue, making them easy to identify. Unfortunately, widespread adoption of the USB 3.0 specification and development of related peripherals has been significantly slower compared to USB 2.0 due to delayed integration of the specification in mainstream electronics. With a limited market and availability of USB 3.0, USB 2.0 specifications and peripherals remain pervasive in mainstream consumer electronics.

In addition to the data rates, different types of USB connectors were developed to keep up with the demands of evolving peripherals. All USB connector types – encompassing the standard, Mini and Micro – have a Type A and Type B connector. Type A is usually found on devices that provide power, such as computers (hosts), and Type B is found on devices and peripherals that receive power (slaves).

The standard USB Type A connector is long, flat and rectangular, and can be found on most computers and hubs. Some common peripheral devices that use this connector are USB flash drives, computer mice, keyboards, and external hard drives. USB Type B connectors are smaller, squarish, and designed for peripheral devices, which are often printers and scanners that can be connected to a computer. USB Type B connectors usually require USB A-B cables. Standard USB connectors, both Type A and B, have four pins, with one for power, two for data, and one for ground.

Because consumer peripherals were shrinking in size, manufacturers found the need to downsize the USB Type B connectors to fit onto smaller devices, resulting in the USB Mini-B in 2000. USB Mini-B connectors usually have five pins, with the fifth pin as an “ID pin” that serves no functionality for the connection; it was meant to allow future upgrades. USB Mini-B connectors have a life cycle of at least 5,000 connects and disconnects, as they were meant to accommodate the mobile nature of devices such as PDAs, MP3 players, camcorders and digital cameras. USB Mini-A and USB Mini-AB (uses the fifth “ID pin”) connectors existed for a period of time, but in 2007, they became obsolete to minimize consumer confusion and to push adoption and development towards the then newly released USB Micro-A, Micro-B and Micro-AB connectors.

Much smaller than the USB Mini connectors but still capable of high speed transfers, USB Micro connectors boast a life cycle of at least 10,000 connects and disconnects – twice the amount of the USB Mini connectors. Its design reduces the wear and tear on the device's connector, thus reducing costly replacement by applying the wear on cables, which are easier to replace. Similar to its USB Mini-AB predecessor, USB Micro-AB connectors on peripherals use the fifth ID pin to facilitate On-The-Go (OTG) functions; such connectors cannot be found on cables. The USB Micro-AB receptacle can accept both Micro-A and Micro-B plugs, thus allowing the peripheral to temporarily adopt the role of a host instead of a slave. This allows users to execute actions such as printing an image directly from a smart phone, rather than needing to upload images to a computer in order to do so. USB Micro connectors have increasingly become the norm on newer mobile devices such as GPS systems, digital cameras, smart phones and PDAs.

While the USB 2.0 specification is compatible with all of the connector types listed above, the USB 3.0 specification only supports standard USB 3.0 Type A and B, USB 3.0 Micro-A/AB and USB 3.0 Micro-B connectors. The USB 3.0 connectors have nine pins, five additional from the USB 2.0 standard, with two differential pairs for SuperSpeed data transfer and one ground for drain wire termination, controlling EMI and maintaining signal integrity. The standard USB 3.0 Type A connectors are backwards compatible with USB 2.0 ports and will carry data from slower speed connections. In contrast, the USB 3.0 Type B connector is not backwards compatible with USB 2.0 or USB 1.1 devices, but will accept their cabling. This is due to the expanded layer on the top of the connector for the additional five pins.

Similar to the design of the USB 2.0 Type B connectors, the USB 3.0 Micro connectors retain the USB 2.0 Micro connector pins and design, but have an expanded side to support the additional five pins. As a result, USB 2.0 Micro plugs can work with the USB 2.0 portion of a USB 3.0 Micro receptacle but not vice versa. It is also pertinent to note that the USB 3.0 Micro-A and USB 3.0 Micro-AB connectors are identical; the naming system retains the nomenclature followed by the USB 2.0 Micro connectors to prevent confusion among consumers.

USB 3.0 also introduces the new Powered-B connector, which enables a USB device to power another USB device, and looks exactly like the USB 3.0 Type B. With two more pins than regular USB 3.0 connectors for power and ground, the Powered-B connector can provide up to 5V, 1000mA of current. All Powered-B devices have their cable hard-wired, negating the need for cables and preventing the risk of running a USB Powered-B device over a USB 2.0 cable or plugging a USB Powered-B device into a USB 3.0 receptacle. The Powered-B connection can eliminate the need for external power and extra cables, such as with a Wireless USB adapter.

Moving forward, plans to implement a faster version of the USB 3.0 were officially announced at the start of 2013, which will double the data transfer rate to 10 Gbps. Given the slow integration of the USB 3.0 to mainstream consumer electronics, widespread implementation of the USB 3.1 specification and development of USB 3.1 peripherals remains to be seen.

About Video Products Inc:
Video Products Inc (VPI), based in Aurora, OH (USA), is dedicated to supplying the highest quality connectivity products to integrators, distributors, IT professionals, and tech-savvy home-users. VPIs product line includes a wide variety of cables, adapters, hubs, switches and splitters. All products are rigorously tested and are backed with a one-year warranty on all parts and labor, and a 30-day satisfaction guarantee. For more information, visit: www.vpi.us