Creating Efficient USB C Pinouts for Any Design

April 27, 2021 , in Blog

When designing circuit boards, you notice early in the process that there is no shortage of commonly used PCBA connectors. These exist to transmit and receive the various power, data and control signals required for electronics operation and functionality. One of the most common connector types used today is the universal serial bus, or USB, found in applications ranging from mobile phones to computers and industrial systems. The newest version, USB C, not only allows for faster transfers but combines the capability to transfer data, audio/visual and power across a single cable.

Designing circuits and laying out boards for this connector type can be a challenge. However, by understanding the USB C pinout—for receptacles and plugs—and following design guidelines, you can achieve the best design for efficient PCBA development.

USB C connector

Understanding the USB C Pinout

The primary advantages of USB C connectors over its predecessors include:

USB C Advantages

  • Single size and shape

The USB C connector is much smaller than the commonly used Type A, and it provides a single connector size and shape, as opposed to the variety of sizes previous USB communication protocols employed.

  • Flexibility

In addition to being backward compatible with prior USB standards, USB C can support other protocols, such as HDMI, VGA, A/V and power transfer over a single cable.

  • Speed

USB C cables support the USB 3.1 standard protocol, which has a transfer rate of up to 10 Gb/s.

  • Power

Up to 100 W of power can be transferred over USB C cables if using the USB PD specification.

  • Bidirectional

For USB C, TX/RX and power are bidirectional.

The USB C Pinout

In addition to the advantages listed above, USB C connectors exhibit full duplexity, which means that data can be simultaneously delivered and received across a single cable. This capability can be seen in the USB pinout for the receptacle and plug, shown in Fig. 1 and Fig. 2, respectively.

Pinout for the USB C receptacle connector

Fig. 1 USB C receptacle pinout

Pinout for the USB C plug connector

Fig. 2 USB C plug pinout

As shown in the figures above, the USB C connector has dual rows of 12 pins. The function of each row is controlled by the CCX–1 or 2–pin. The SBU pins are not used for USB communications, but alternate modes. There are five alternate modes for USB C:

USB C Alternate Modes

  1. DisplayPort
  2. Thunderbolt
  3. HDMI
  4. Mobile High-Definition Link (MHL)
  5. VirtualLink

Modes 4 and 5 from the list above have been announced; however, they are not available for utilization. It is also noteworthy that there are no D+ and D- pins for row B of the plug, as they are unnecessary.

Designing PCBA Layouts With USB C Connectivity

Including USB C connectivity in your PCBA design can provide a powerful addition to functionality and capability. However, you will need to decide what layout option to employ, and this decision can significantly impact the development cycle time for your design.

PCBA Layout Options

When considering PCBA layout options that include USB connectivity, constraints emerge due to installation location, available space or external connection requirements. Within the confines of these restrictions, there are two implementation options for USB C pinout connectivity.

Option #1: Adding a USB C pinout connection board to an existing design

If you are upgrading an existing design, even from a prior USB connection version to USB C, the simplest and fastest option is to add a USB C breakout board. This allows you to add connections to specific pins. Many of these boards are currently available and can facilitate fast bring up—especially when used with reference and other development board types.

Option #2: Creating a new custom USB C pinout connection layout

If you are designing a board to take advantage of the enhanced capabilities of USB C connectivity, a custom design is likely required. In this case, the development cycle for your board should be similar to the development and introduction of a new product.

For Option #2, you should apply the best design principles to optimize reliability and manufacturability. These principles include early collaboration with your CM, compliance with your DFM and DFA rules and guidelines, prioritization of signal and power integrity, and the application of good grounding principles for the most efficient PCBA development.

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Tempo Automation is the industry leader for fast and precise PCBA manufacturing for prototyping and low-volume production. We specialize in building complex boards that fully reflect your design intent, including multisignal functionality that enables full utilization of the capabilities of employing USB C connectivity.

And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on the USB C pinout and how to optimize your board with this connectivity, contact us.

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