How to Use USB in Your Next Design

USB ports are one of the most popular connectors around the globe. Nowadays, almost every electronic gadget and device that utilizes wired connectivity uses USB connectors. It has become a standard interface for computers and other consumer electronic devices. But what is USB, and how do you integrate one in your next PCB design? Let’s find out.

What is USB?

USB stands for Universal Serial Bus, an industrial standard that specifies the connection protocol and power limits while communicating between two or more devices. The technology allows us to connect many devices such as smartphones, computers, cameras, and printers to one another. This is why we can use the same USB keyboard with our PC or smartphone seamlessly. 

USB Types and Specifications

Depending on the application, there are quite a few USB types available. And sometimes, distinguishing between them is confusing. For the sake of simplicity, we will cover only the most commonly used USB types.

There are three types of USB which are

Type A Type B Type C

They are further categorized as Standard, Mini, and Micro, depending on the port’s physical shape. Among which Standard Type A connectors are the ones that you can find on most of the devices. Standard Type-B connectors are used in some old printers and cameras. Micro USB Type B is mostly used in mobile devices and small accessories due to its small size. USB Type C is relatively new, and it offers some impressive specifications in terms of data transfer speed and high power handling capability. It is designed to replace both A and B types with smaller ports to support mobile devices’ small form factors better. That’s why it is getting more and more popular these days.

Then there is another USB classification based on generations:

USB 1.x USB 2.0 USB 3.0 USB 3.1

The first generation USB types are mostly outdated due to the vast improvement in the second generation. Hi-Speed USB 2.0 can transfer data at the rate of up to 480 megabits per second (Mbps), or 60 megabytes per second (MBps). The current-carrying capability also increased to 2A, which enables to charge a device even faster. The latest version of the USB protocol, USB 3.0 and 3.1, can transfer up to 10 Gbps rates. Simultaneously, its intelligent power delivery (PD) system allows you to deliver up to 100 watts of power without an issue, hence it becomes a genuinely universal connectivity standard for modern devices. That’s why most of the latest devices use USB 3.0 and 3.1 for improved performance and speed.

Each USB version is both backward and forward compatible, meaning you could plug a USB 3.1 connector on the USB 2.0 port or vice versa. But the data transfer speed and power handling capability will be limited to the lower version port.

Pin Configurations

A Standard USB type A or Type B typically has four pins:

VCC DATA+ DATA- GND

On some USB ports, you may have the 5th pin. This is mainly seen on the micro and mini USB ports and is labeled as an ID pin. This pin is for On-The-Go(OTG) to select which device is the host or slave. The micro-A plug has the ID pin grounded, while the ID in the micro-B plug is floating. The device that has a micro-A plugged in

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