What is USB Type-C?

This is a basic explanation of USB Type-C. It also describes the differences from traditional USB-A and USB micro-B. With 24 pin assignments, USB Type-C is a new standard connector that is reversible and can be used for both data transfer and power delivery.

What is USB Type-C?

USB Type-C is a new connector standard for USB. It is also referred to as USB Type-C™ or USB-C™, and this labeling is a registered trademark of the USB Implementers Forum, a non-profit organization that defines USB specifications.

USB Type-C was officially announced in 2014. Recently, USB-C ports have been featured on PCs from manufacturers including Apple, and USB-C AC/DC Power Adapters — Desktop & Wall-Mount are becoming more common in everyday life. The latest iPhone 11 Pro and iPhone 11 Pro Max, recently announced, come with an 18W USB-C compatible adapter.

Simultaneous Power Delivery and Data Transfer

The appeal of the USB Type-C connector lies in its ability to deliver power and transfer data at the same time. It is expected to become increasingly widespread as it will be utilized in a variety of products and standards, including USB Power Delivery (PD) and Quick Charge protocols.

The recently announced iPhone 15 from Apple also adopted USB-C, generating buzz over its ability to charge other devices—like iPads and iPhones—directly. This could indicate a future shift from Thunderbolt to USB-C.

Even Faster Data Transfer Than Before

Some USB-C connectors now support USB 3.1 Gen 2, which enables data transfer speeds approximately twice as fast as traditional USB 3.0—up to a theoretical 10 Gbps. This makes it an ideal connector for high-speed data transfer and maximizing the capabilities of USB PD. (Note: Not all USB Type-C connectors support USB 3.1.)

Overview of the History of USB Standards (from 1.0 to USB4)

Let’s take a moment to summarize the history of USB.

Connector Situation Before USB’s Introduction (Pre-1996)

Before USB was introduced, PC manufacturers used various proprietary connections for data transfer—for example, serial ports, parallel ports, special plugs, connectors, and cables. These often required dedicated drivers or expansion cards. Data transfer was slow, maxing out at 100 KB/s for parallel ports and 450 kbps for serial ports. Additionally, users often had to disconnect or reboot the computer when connecting a new device.

Initial USB development began in 1994 by the USB Implementers Forum (USB-IF). Pre-release versions USB 0.8 and USB 0.9 were announced but never commercially released. USB 0.99 followed in 1995, also unreleased commercially. These early developments were vital steps toward industry-wide standardization.

Introduction of USB 1.0 (1996)

In early 1996, USB 1.0 debuted as the first official USB standard. It offered data transfer speeds of 1.5 Mbps (low-speed) and 12 Mbps (full-speed). USB 1.0 featured automatic device configuration, allowing users to avoid manual settings. It supported hot-swapping, so devices could be connected without restarting the computer. Although it was innovative, it wasn’t widely adopted at the time due to the limited number of compatible devices.

USB 1.1 (1998)

In 1998, USB 1.1 was released as an improved version of USB 1.0, maintaining the same data speed but supporting even slower operation for low-bandwidth devices. This encouraged PC makers to replace serial and parallel ports, sparking broader market interest. USB 1.0 and 1.1 used standard rectangular Type-A and square Type-B connector shapes.

USB 2.0 (2000)

USB 2.0 debuted in April 2000 with a maximum data rate of 480 Mbps (real-world speed about 280 Mbps). It enhanced plug-and-play support and power delivery—benefitting multimedia and storage applications. USB On-the-Go was introduced, enabling direct device-to-device connections. USB 2.0 supported Type A, B, C, and mini/micro A/B connectors. The first USB flash drives also emerged in 2000, driving further adoption of USB.

Wireless USB and USB Micro Overview (2005)

Wireless USB (W-USB), announced in 2005, was a now-obsolete short-range wireless standard (10 meters) with 480 Mbps speed. USB Micro arrived in 2007, smaller than mini-B, and became the standard for Android devices due to its compact size and support for fast charging and data. It served purely as a physical connection, not a data protocol.

USB-C 3.0/3.1/3.2 and the Advent of Type-C (2008–2017)

USB 3.0 (now USB 3.2 Gen 1) launched in 2008 to meet growing storage and bandwidth needs, offering a max 5 Gbps transfer speed and full-duplex data transfers. In 2017, USB 3.2 replaced USB 3.0 and 3.1, improving speeds up to 20 Gbps with USB 3.2 Gen 2x2. The USB Type-C connector was introduced—compact, reversible, and adaptable.

This marked the debut of the Type-C connector.

Latest Standard USB4.0 (Since 2019)

The latest USB standard is USB4.

Released in 2019, USB 4.0 is based on the Thunderbolt 3 protocol. It supports data transfers up to 40 Gbps and power delivery up to 240 W. It uses the same Type-C connector and is backward-compatible with USB 2.0 and 3.2 (with potential speed reduction). Intelligent power delivery allows up to 240 W of bi-directional current flow.

(USB History Timeline)

Compare with Conventional Connector Shapes

As shown here, the USB Type-C connector is closest in size to micro-USB and is compact and oval-shaped. The leftmost connector is likely USB Type-A, the most familiar to users. USB Type-A is not reversible, making it easy to insert incorrectly. USB Type-C, on the other hand, is reversible and avoids such frustration.

About USB Type-C Pin Assignments

USB Type-C Pin Assignments Are Cleverly Arranged

The Type-C pin layout is as follows:

There are 8 data lanes (TX1+/TX1-, RX1+/RX1-, RX2-/RX2+, TX2-/TX2+), central D+/- for USB 2.0 communication, CC1/CC2 for configuration and detection, VBUS for power, and GND for grounding. The layout allows for reversible insertion by assigning symmetrical pin functions.

Comparison of Pin Assignments by Mode/Use Case

For USB 2.0/1.1

In USB 2.0/1.1 mode, the following lanes are used:

VBUS and GND provide up to 5V 500mA, and the D+/D- pins handle data. When connecting USB-C hosts to USB 2.0/1.1 devices, Rd resistors are needed on CC pins.

For USB 3.0/3.1/3.2

In USB 3.0/3.1/3.2 mode, the following lanes are used:

Up to four TX/RX high-speed lanes are used for throughput up to 5–20 Gbps. One CC pin is used for mode negotiation. USB 3.1 allows up to 5V 900mA, with options to deliver 5V 3A.

USB-C Is Ideal for Compact, Thin Devices

USB Type-A gave way to MicroUSB and Mini-USB due to device miniaturization. USB-C is about one-third the size of Type-A, making it well suited for small and thin devices.

Alternate Mode Support for Streamlined Connections

Video and audio connectors come in various standards—HDMI, DisplayPort, VGA, Thunderbolt 3. USB-C supports Alternate Mode, which can handle all these signal types, combining data, power, and display functionality.

In the use case above, the left port charges a smartwatch via USB-A, the middle port outputs video to a monitor via HDMI, and the right port charges both the smartwatch and laptop—replacing three cables with one.

Alternate Mode uses certain lines in USB-C 3.1 cables, including four high-speed lanes, two sideband pins, two USB 2.0 data pins, and one config pin. Alternate mode is set through vendor-defined messages (VDMs) on the config channel.

In 2018, Alternate Mode Partner Specification was defined based on five systems. Alternate mode is optional and not mandated by USB-IF. The USB-IF verifies port labeling accuracy with partners.

Lanes used in Alternate Mode:

In Alternate Mode, SBU1/2 are used for low-speed links. Up to four high-speed links can be used as needed. If only two are used, USB 3.0/3.1 links can also be established. CC handles negotiation, and D+/D- can provide USB 2.0 signaling.

Audio Accessory Mode

Devices with USB-C can support analog headset adapters with 3.5mm jacks and allow 500mA device charging. This allows users to listen to analog audio via USB-C while charging their phones. USB-C audio may eventually replace the 3.5mm headphone jack entirely.

Summary

How does USB-C differ from USB-A and USB Micro-B? Here’s a summary:

• Reversible plug orientation for easier insertion
• Greater power delivery (5.0V/1.5A to 5.0V/3A; up to 100W with PD)
• More pin assignments (from 4–5 to 24 pins)
• Configurable on both host and device sides
• Faster data transfer
• Supports video output

USB-C Photos and Diagrams

Compared to older standards, USB-C offers improved convenience.

We also offer custom adapters with USB-C connectors—for inquiries, please feel free to contact us.

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