Understanding USB: Speed, Connectors and Functionality

When the USB connector first came on the market, it was revolutionary in that it replaced a collection of confusing connector types: serial ports, parallel ports, PS/2 connections, joystick ports... all of which required dedicated hardware and drivers.

The now-ubiquitous USB connector slims down the number of ports required on a computer, paving the way for smaller, lighter and more portable devices. It simplifies development of new products and improves speed to market. And it makes life easier for consumers when they don't need a drawer full of cables to connect various peripherals and devices.

However, as USB protocol has evolved, it's become confusing in its own way. Let's take a closer look at the elements distinguishing USB standards. Quite simply, these are speed, connector types and added functionality.

USB cable

1. USB Speed Standards

Your USB connections are about to become faster! Products compatible with the new USB 3.1 Gen 2 standard will start to hit the market soon. This latest generation promises to take connectivity to the next level, with data transfer rates twice as fast as USB 3.0 (also known as USB 3.1 Gen 1):

2. USB Connector Standards

USB Type-B

Most commonly used to connect printers and external hard drives to desktop computers, the Type-B port actually has two different configurations. One is specific to USB 1.1 and 2.0 speed protocols, while the other is for use with the USB 3.0 and later spec.

USB Mini-B

The Mini-B connection is most often used by portable electronics such as digital cameras, MP3 players and some cell phones, and only with USB 1.1 and 2.0 speeds. There are both four-pin and five-pin versions of the Mini-B connector.

USB Micro-B

The Micro-B connector has one configuration for USB 2.0 and a different configuration for USB 3.0 and later. The Micro-B connector is found on many popular models of Android smartphones and external hard drives.

USB Type-C

Developed to support devices with a smaller, thinner and lighter form factor. Type-C is slim enough for a smartphone or tablet, yet robust enough for a desktop computer. It also has the advantage of a reversible plug orientation and cable direction, eliminating the guesswork about which direction the connection goes.

3. USB Functionality

On the most basic level, USB standards simply let a host, such as your computer or tablet, communicate with peripherals and other devices. But as specifications evolve, USB has become more than a mere data interface. Below are the latest USB functions available on many of today's devices. A device may support one or more of these functions:

Power Delivery

Up to 100W of power can be delivered across a single USB cable, eliminating the need for a separate power brick. This is especially useful for peripherals that draw higher power levels, such as hard drives and printers. Not all devices will support USB Power Delivery, however; consult your device's specifications chart or owner's manual if you are uncertain.

Examples of USB Power Delivery
laptop powering external hard drive

A power-hungry device, such as a hard disk drive, can be powered directly from a laptop.

monitor powered by wall outlet powering/charging a laptop while displaying

A monitor powered by a wall outlet can power or charge a laptop while displaying.

USB port in wall outlet powering/charging a laptop

A USB port in a wall outlet can supply power to or charge a laptop.

Battery Charging 1.2

If you've ever recharged your phone from your PC's USB port, you know how useful this USB function can be. The BC 1.2 spec defines a new type of port, the charging port, that meets standards to ensure your battery will recharge safely and consistently. It also allows a device to pull more power than a standard USB port for faster charging. A normal USB 2.0 port provides up to 500mA (0.5A) and a USB 3.0 port provides up to 900mA (0.9A). The output of a BC 1.2-compliant port puts out up to 1.5A, even while transferring data. It also allows the device being charged to communicate its charging requirements to the USB charger, ensuring an optimal charge.

USB On-the-Go

USB OTG allows mobile devices such as a smartphone or tablet to act as a host to other USB devices such as flash drives, keyboards and mice. With USB OTG, a mobile device can utilize the functionality of the peripherals while still being able to connect to a computer and present itself as a mass storage device to be used on the computer. USB OTG-compliant devices will require an OTG adapter to allow for the connection of peripherals.

DisplayPort Alt Mode

With DisplayPort Alt Mode, USB-C connectors and cables have the ability to transmit both USB data and VGA, DVI, HDMI or DisplayPort video and/or audio. Adapters are available to connect DisplayPort over USB-C to VGA, DVI, HDMI and DisplayPort monitors. DisplayPort Alt Mode does not require the use of drivers, making it plug-and-play.