What is USB C? A Quick Primer
The USB Type-C connector is the standard in many modern smartphones, laptops and tablets today—it's definitely here to stay. Even though USB-C is quickly becoming the standard, it’s not always easy to spot the differences in USB connector types, USB ports, or USB cable types.
What most of us think of, when we hear USB
What Makes the USB Type C Connector Special?
For this article, we want to focus our attention on the USB C Connector, as it’s quickly becoming the standard connector type. Here are some quick facts and advantages for Type C connectors:
- Convenient: Type C connectors are reversible and look like rounded rectangles
- Modern: Even the oldest version available is USB 3.0, with transfer speeds of 5 Gbps.
- Fast Charging: USB-C connectors are usually equipped with the 3.1 standard, enabling fast charging on eligible devices. More details on this later.
- More universal: many modern devices have USB-C ports as the standard, and USB cables increasingly have USB-C connectors on both ends, eliminating any need for different types of connectors.
Some things to keep in mind, despite the advantages of USB-C:
- USB-C doesn't always mean faster. There are USB versions with legacy Type A/B connectors that have equal. or faster transfer speeds than the oldest USB-C.
- Even though the newest devices commonly have USB-C, there are still many devices that use USB-A ports. Examples include: Apple's iPhone power block, Apple Watch magnetic charger, wireless mouse receivers, PS4 controllers, etc. It's still common to use a USB cable that has Type-A connector to Type-C connector.
What is Fast Charging?
You may have heard all kinds of vocabulary: Power Delivery, Thunderbolt, QuickCharge, etc. What do all these mean? First, we have to understand how devices and their batteries charge.
How fast charging works
The amount of charge a battery receives is determined by watts (W), which is a simple function of volts (V) times amps (A). Greater current (measured by amps) and higher voltages (measured by volts) charge batteries faster, but there’s a limit to what they can take and thankfully, this is controlled by a charge controller (IC) which protects the battery against dangerous spikes in current. The charge controller draws is generally controlled by the phone’s software.
Here's a quick summary of each USB generation and their power capacity:
Unless you’re still rocking a Palm Pilot from the early ’90s, chances are your smartphone recharges via USB cable. There’s a really good reason: Besides the fact that USB cables are relatively easy to find these days, USB has a really robust, well-defined charging standard called the USB Power Delivery Specification.
The USB Implementers Forum specifies four types in total, one for each corresponding USB specification: USB 1.0, 2.0, 3.0, and 3.1.
A typical USB 1.0 and 2.0 plug can deliver up to 5V/0.5A (2.5W).
That’s the charging rate of a typical phone, and it doesn’t amount to a lot of power. An iPhone charging at 2A over USB uses 5V x 2A = 10W. The average incandescent light bulb, by comparison, draws about 40W of power.
By default, USB 3.0 ports push 5V/0.9A (4.5W).
USB-C, the oval-shaped reversible plug on newer smartphones, is a different animal altogether. It’s technically capable of carrying the USB 2.0 spec, but most manufacturers opt for USB 3.1, which can potentially deliver a much higher voltage.
Many USB 3.1 devices take advantage of the USB Power Delivery (USB-PD) spec, which has a maximum power output of 20V/5A (100W). Smartphones don’t usually draw that much power — manufacturers commonly stick with a lower amperage (like 3A), but it’s a boon for USB-C laptops like the MacBook Pro and Google Chromebook Pixel.
Slightly complicating things is the Battery Charging Specification, which deals specifically with power drawn from a USB port for charging. The most recent spec, Rev 1.2, defines three different sources of power: Standard downstream port (SDP), charging downstream port (CDP), and dedicated charging port (DCP). CDP, the spec in modern smartphones, laptops, and other hardware, can supply up to 1.5A.
Fully compliant smartphones and chargers respect the limits of USB 2.0 and BC1.2, but not all phones and chargers are compliant. That’s why, generally speaking, smartphones always default to the lowest charging speed.
The USB specs are more like guidelines than dictum, though. Fast-charging standards like Qualcomm’s Quick Charge and Samsung’s Adaptive Fast Charging exceed the USB spec’s voltage parameters, but on purpose — that’s why your phone is able to recharge in minutes, rather than hours.
Fast charging standards: What’s the difference?
USB Power Delivery
The USB Power Delivery (USB-PD) standard was developed by the USB Implementers Forum (USB-IF) and it’s a standard that any manufacturer can use on any device with a USB port. It’s capable of delivering up to 100W, so it’s suitable for use with all kinds of devices beyond smartphones including some laptops, provided they have a USB-C port. USB-PD brings other benefits, too. The direction of the power is not fixed, so you will find portable battery chargers, for example, that have a USB-C port that can be used both to charge another device or to charge the battery pack itself. USB-PD also only provides the power the device needs, so the same USB-PD charger could charge a smartphone at top speed, but then also charge a laptop at its top speed.
Different manufacturers employ the USB-PD standard differently. Here’s how Apple and Google use it, for example.
USB Types: Connectors, Cables, Ports
USB Connector Types:
You may have heard people refer to USBs as “Type-A”, “Type-B”, or the modern standard: “Type-C”, sometimes simplified to USB-C. Generally, people are referring to the connector types, meaning the tips of a USB cable. Every USB cable has two connectors, and they’ve historically not been the same type. For a long time, many phones charged using a USB cable that had Type A on one end, and Type Micro B on the other end. It looked like this:
USB Type Micro B
Today, many USB cables have Type A and Type C connectors, which is especially useful when connecting older devices that have Type-A ports to newer devices with Type-C ports.
Historically, USB cables most commonly had Type A to Type B connectors. It’s important to note that the connector themselves don’t always dictate important metrics like transfer or charging speeds. Generally, it’s the version of USB at use and the port that determines transfer and charging speeds. Here’s a quick visual to help you identify each USB connector type:
Type A to Type B connections are common and they’re generally seen when connecting peripheral devices to PCs—think printers to PCs.
Micro USB connectors are thinner and slimmer versions of regular Type A/B. These are also common and were used as the connectors for phone charging for some time. A common modern version of these connectors is in a Micro USB to USB C cable.
Type C USB connectors are the latest iteration of connector types. Today, they are the standard in the latest devices like laptops, smartphones and tablets. They were built to be reversible, thinner, faster, and more universal. Devices must have a USB C port.
Lightning connectors are not technically an official USB connector type, however, they’re so common it’s worth mentioning. These are proprietary Apple connectors and only seen with charging Apple devices. Because Apple devices are so common, one of the most common USB cables is Type A connector to Lightning.
USB Cable Types:
USB Cables come in many forms. For this article, we refer to the cable as the long wire-y portion of a cable. Primarily, when thinking about the cable itself, there is the construction and the length. When someone refers to a USB cable as a USB Type C Cable, they generally mean a USB Cable that has the same Type C connectors on each end, but that doesn’t mean that Type C connectors cannot be paired with other USB connector types. In fact, because many devices today still use USB connector types older than Type C, USB C cables often have different connectors like Type A to Type C.
Be wary of which USB cable length you need when buying: a 6 in. cable versus a 6 ft cable makes a big difference. When in doubt, we recommend buying the longer cable for flexibility.
Types of USB Ports:
The USB Port combined with USB Connector Types determine the transfer speed of data and also determine the "generation", or "version" of USB used. When transferring data, the speed is always limited by the lowest maximum speed on either the port, or the connector. Today, there are many versions of USB, each with their own theoretical transfer speeds and it can get overwhelming quickly. Since our focus is on USB-C, we should know that the default protocol for USB-C connectors is USB version 3.0, which means it can transfer data at speeds up to 5Gbps (gigabits per second), twice as fast as its predecessor. Here is a quick runthrough of different USB versions, common connector types, and their transfer speeds: