An Overview of USB Type-C in Power-Only Designs

With the first USB standard being introduced back in 1996, USB connectors and their associated standards have seen a multitude of changes over the years in terms of their physical connector type, data rates, and power transfer capabilities. When USB Type-C® entered the fold in 2014, it represented the latest physical standard, affording users greater capability and flexibility due to its bi-directional, reversible package, faster data transfer speeds, and higher power specification. A USB connector is ultimately tied to these three different, but associated, standards: the physical connector, data transmission protocol, and power delivery. However, confusion often arises when looking at the relationship between the standards. Before discussing the new trend of power-only USB Type-C connectors, it is worth clarifying the connection of the various USB standards.

Understanding the USB standards

From a high level, the latest USB Type-C standard defines only the physical connector that users see in many of today’s cell phones and electronic devices. Data transfer protocols, such as USB 3.2 and even now with USB4, apply only to the electrical signal. Although often utilized together, an engineer could create a system using the USB 3.2 data transfer specification and their own proprietary connector not conforming to the physical USB connector standard.

The same goes for the USB Power Delivery (PD) specification. Due to its design, a USB Type-C connector supports up to a 5 A current rating and 20 V_DC voltage rating for up to 100 W of power transfer capability defined in USB PD 3.0. Released in 2021, the USB PD 3.1 standard, has since expanded Type C’s power transfer capability up to 240 W. While USB Type-C connectors can support USB PD, the Power Delivery specification is really governed by the charging circuit and only limited by the voltage and current capabilities of the physical connector. However, this higher power capability supported by USB Type-C connectors has led them to a new world of power opportunities.

Figure 1: Advancement of USB power levels (Image source: Same Sky)

USB Type-C connector advantages in power designs

Housing sixteen data transfer contacts, four power contacts, and four ground contacts, a standard 24-contact USB Type-C connector supports up to 240 W of power transfer. This makes the USB Type-C connector an intriguing solution for power applications with the ability to replace a standard dc power connector even when data transfer is not needed.

Standardization represents one of the main advantages of utilizing USB for power delivery. USB connectors are widely adopted across many different industries and Type-C continues to establish itself as the universal connector in phones and mobile devices. Because of this, the European Union has already moved to adopt the USB Type-C connector as the standard for all future devices bought and sold in its region. To an end-user, the convenience of only needing a single, off-the-shelf cable to interface with a wide variety of products cannot be understated. OEMs also benefit from a stable supply chain as USB connectors are simple to find and their standardization assures a level of interoperability. Because of this standardization, the challenges of design integration are also reduced. In addition, USB Type-C connectors typically offer a smaller package size than a number of barrel connectors as well as high reliability and longer life with a 10,000-mating cycle rating.

Power-only USB Type-C connectors

Due to the advantages listed in the previous section, Same Sky has developed power-only USB Type-C receptacles for applications where charging or power delivery is the sole intended use. Same Sky 60 W or 90 W power-only USB Type C receptacles remove the sixteen data transfer contacts and two of the ground contacts, leaving only four power contacts and two ground contacts.

Figure 2: 24-contact Type-C vs 6-contact power-only Type-C (Image source: Same Sky)

By removing the sixteen contacts, the simplified design of the connector leads to a significant cost reduction with only six contacts compared to a standard 24-contact Type-C. This not only reduces the part cost, but it also decreases the complexity and failure rate with less contacts and associated solder joints to fail. Although these power-only USB Type-C connectors do not transfer data, they are still compatible with any standard data+power USB Type-C cable. This adds to their convenience with no additional hardware or requirements when interfacing between the connector and cable.

Note that with the data transfer pins having been removed, the USB 3.0 power negotiation process does not take place, meaning that the charging device will revert to the USB standard power transfer rate of 5 V and 1 A. In all other instances, the connector will function like any other power jack with the charging governed by the adapter/charging circuit.

Additional Power Scenarios

Although a suitable option for a variety of applications and designs, dedicated power delivery options, such as dc power connectors, still have their place. Foremost, with a 240 W power transfer limit, USB Type-C connectors are simply not an option for designs requiring more than 240 W. However, the USB PD 3.1 does open up even further power capabilities compared to the previous 100 W limit. While standardized footprints offer benefits in many scenarios, there are likely instances where another footprint or package type might be a more suitable option. In other words, when a more customized connector is needed, USB Type-C could be restricted by its standardized sizes and limits. For more information on when other power connectors can still be the best solution, read Same Sky blog on selecting a dc power connector.

Looking Ahead with USB Type-C

USB Type-C connectors and their widespread adoption have given engineers a new avenue in which to view power management and transmission. While not an end-all solution, Type-C’s power capabilities up to 240 W and global standardization will give it a strong foothold in a wide range of products and applications. With their low cost and simplified design integration, Same Sky power-only USB Type-C receptacles offer engineers an appealing option when power delivery is the sole function.

Same Sky currently offers horizontal or vertical 60 W or 90 W power-only USB Type C receptacles with a maximum 3 A current rating and 20 V_DC or 30 V_DC voltage rating.