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Understanding USB and Thunderbolt: Speed, Connectors and Functionality

For years, USB connectors have been effective in reducing the number of ports required on a computer and paving the way for smaller, lighter and more portable devices. However, as new USB standards bring more speed, power and versatility to market, they also bring a complex assortment of features and capabilities to consider when selecting the right technology for your application.

What is USB?

USB is a series of standards (see Table 1) that specify how cables connect, communicate and exchange power with electronic devices and related peripherals. Each USB standard has its own data transfer speeds, maximum power and maximum cable lengths. They all also operate with specific types of USB cable/port connectors.

What is Thunderbolt?
Thunderbolt logo

Thunderbolt is an interface technology protocol designed for high-speed transfer of all types of data along a single cable. Thunderbolt cables do not have their own connector designs, relying instead on existing types in the market.

Look for the Thunderbolt icon on a cable or device port to indicate its use of Thunderbolt technology.

Thunderbolt vs. USB-C

Like USB, Thunderbolt technology comes in different standards that have their own performance ratings and work with different types of connection hardware. This includes Thunderbolt 2, which works with Mini DisplayPort connections, and the newest Thunderbolt 3, which works with USB-C connections.

Not all USB-C connections use Thunderbolt technology (as shown in Table 1), but those that support Thunderbolt 3 can provide unprecedented speed and power delivery.

Let's take a closer look at the elements distinguishing USB and Thunderbolt standards. Simply put, these are speed, connector types and added functionality.


1. USB and Thunderbolt 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.

* Cable length is the length covered by the specification. Longer lengths can be achieved using active cables and in some cases, longer passive cables.
** USB-C is also called USB Type-C or simply Type-C.

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). A BC 1.2-compliant port provides 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.

Thunderbolt 3 technology supports vibrant 4K video resolution on dual DisplayPort displays simultaneously, an ideal feature for digital signage and high-performance gaming.


4. USB Docking

Boost the functionality of the USB or Thunderbolt port on your MacBook or laptop with a portable, smartphone-sized USB docking station. The latest Thunderbolt 3 docks offer up to a blazing 40 Gbps bidirectional data transfer speed, ideal for quickly transferring large media files between devices. When Wi-Fi is weak or unavailable, they can provide access to a wired Ethernet network. They offer a simple way to add robust Thunderbolt to HDMI or Thunderbolt to DisplayPort functionality to a device, and support playing true 4K high-resolution video and digital audio on two large displays simultaneously.

Clear List

Need help with your purchase?
We're always available to help with questions, including product selection, sizing, installation and product customization. Call us at 1 773.869.1774 or email presaleshelp@tripplite.com.