USB4 Specification Guide – USB 4 Cable, Connector, and Compatibility

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Quick Answer

USB4 is a high-speed connectivity standard that offers several impressive statistical specifications. It features a maximum data transfer rate of up to 40 Gbps, significantly faster than its predecessors. USB4 can provide power delivery ranging from 5V to a remarkable 48V, with a maximum power output of 240W, making it capable of charging a wide range of devices. This standard utilizes the USB-C Type 2.1 connector, ensuring compatibility and a unified experience across various devices and platforms.


USB technology has come a long way since the introduction of USB 2.0, which was the gold standard for nearly a decade. In those early days, USB 2.0 offered various connector types, a cable length of up to 3 meters, and a maximum throughput of 480 Mbps. Fast forward to today, and we have the USB4 standard, which utilizes the powerful USB-C Type 2.1 connector, offers blazing speeds of up to 40 Gbps, and can deliver anywhere from 5V to a staggering 48V, with a maximum power output of 240W.

A New Chip

emarker

However, USB4 isn’t just another step in the evolution of USB technology; it represents a significant leap forward that introduces new concepts and technologies. One such innovation is the “E-marker chip.” This chip is a vital component of any USB-C cable that supports or exceeds 60 watts of power delivery capacity. Acting as an electronic label, it provides crucial information such as cable length, maximum supported current, vendor and product IDs, and much more.

The E-marker chip inside USB-C 2.1 cables communicates with connected devices to negotiate power delivery and data transfer capabilities, optimizing charging speeds and data transfer rates. This intelligent communication verifies that devices receive the right amount of power without overloading or causing damage. Without an E-marker, a Thunderbolt host may reject the cable, assuming it’s a lower-capacity USB cable. E-mark cables, with their integrated E-marker chips, provide incredible speed but also protection to devices during usage.

Support

USB4 brings a wealth of new capabilities to the table, but not all computer systems can fully embrace its potential. Some motherboards and CPUs do not yet support the complete range of USB4’s features. To fully unlock USB4’s capabilities you will need a USB4-compatible device. It guarantees that your system possesses the required components and drivers to make the most of this high-speed standard.

usb3.2 vs 4

In contrast, USB 3.2, the predecessor to USB4, is supported by virtually every motherboard. It is backward compatible with USB versions 2.0 and 3.0, supports power delivery for charging devices, and introduced alternate modes.

USB4 builds upon this foundation by taking a significant step forward, not only maintaining support for USB 2.0 and 3.0 and enhancing power delivery but also adding PCIe support. This makes USB4 an even more comprehensive and powerful connectivity standard, further expanding the possibilities for high-speed data transfer and versatile device connectivity.

Alternate Mode

These alternate modes are where USB4 truly shines. They enable USB to handle various data protocols without requiring special adapters. However, keep in mind that your operating system must support these alternate modes for them to work effectively. High-end displays, in particular, make excellent use of these modes. They offer support for Thunderbolt, power delivery of up to 96 watts, DisplayPort, and HDMI, all through a single USB-C connection.

When USB 3.2 and USB4 switch to alternate modes, they undergo a transformation. Pins are repurposed, cables are reconfigured, and signal conditioning types and directions are adjusted to accommodate various functions like Thunderbolt and DisplayPort.

USB-C 2.1

A significant shift with USB4 is the exclusive use of the USB-C connector. This means that all USB4 cables will be USB-C to USB-C, offering a more unified experience. USB4 devices can support up to 20V of power delivery. Most laptops comfortably run on less than 20V, which means you can even charge your laptop through your display.

usbc 2.1

In 2021, the USB-C Type 2.1 specification was introduced, increasing the power capacity of cables and connectors by an impressive 2.4 times, from 100W to 240W. This enhancement opens up possibilities for charging larger devices such as 4K monitors, e-bikes, and gaming laptops using this versatile connector.

Behind the scenes, USB technology relies on an interface chip or bridge chip, serving as the intermediary between USB and other interfaces like NVMe hard drives. The quality of this bridge chip can significantly impact performance, and careful engineering is essential to avoid bottlenecks in data transfer speeds when dealing with two different protocols.

USB 3.2 vs USB4 Speed


The “number of lanes” and “aggregate bandwidth” in USB standards play a crucial role in determining data transfer speeds. A “lane” in this context represents a distinct data pathway or channel for transmitting information. The more lanes a USB specification utilizes, the greater the potential bandwidth for data transmission.

Aggregate bandwidth is the total data throughput capability of a USB standard, which is calculated by multiplying the signal rate by the number of lanes. This measures how much data can be transmitted simultaneously across all the lanes. Essentially, it quantifies the total capacity for data transmission. As you increase the number of lanes or the signal rate, you enhance the potential aggregate bandwidth.

USB4 achieves faster speeds through a combination of factors. It utilizes the USB-C Type 2.1 connector with increased power capacity. Additionally, advanced signal conditioning and data encoding techniques minimize interference. These innovations collectively drive USB4 to deliver significantly faster data transfer speeds compared to earlier USB standards.

Inside the Cable

inside cable

Deep within the unassuming exterior of a USB4 cable lies a remarkable feat of engineering. Instead of the typical mishmash of wires and insulation, a USB4 cable boasts a sophisticated interior arrangement consisting of eight individually shielded micro coax cables. This intricate construction is the secret sauce that allows USB4 to achieve its incredible data transfer speeds.

Each of these eight micro coax cables is individually shielded, which means they are protected from external interference, electromagnetic noise, and signal crosstalk. Isolating each cable ensures that data signals can travel through the cable without degradation or interference, maintaining the integrity of the transmitted information.

This design effectively transforms the USB4 cable into more than just a cable; it becomes a transmission line similar to what you might find in high-speed data communication systems. The transformation into a transmission line is pivotal because it enables USB4 to handle speeds much higher than previous cables.

Inside the Connector

This diagram is the schematic representation of the arrangement and function of each individual pin within a USB-C connector.

usbc pinout

Understanding the USB pinout is essential to grasp how all these components work together:

  • A2,A3,A10,A11,B2,B3,B10,B11: These are the differential signal pairs responsible for the 40 Gbps data transfer.
  • A6,A7: These pins are dedicated to backward compatibility with USB 2.0 data.
  • A8,B8: Sideband pins used exclusively for alternate modes like Thunderbolt.
  • B5,A5: These pins handle configuration and power distribution, determining the plug’s orientation.
  • A4,A9,B4,B9: The largest wires in the cable, designed to deliver high current at various voltages.
  • A1,A12,B1,B12: Ground cables, providing essential grounding for all signals.

This pin configuration is meticulously designed to reduce crosstalk, electromagnetic interference (EMI), and ensure maximum isolation for all signals.

usbc copnnecotr

Inside a USB connector, there are typically four longer copper areas or “lands,” and they are designed as ground connections.

Ground connections are important for establishing a reference voltage and ensuring proper electrical connectivity when you plug in a USB device. These ground connections are usually among the first to make contact when you insert a USB plug, helping to establish a stable electrical connection.

USB connectors are designed with durability in mind, often rated for over 5,000 mating cycles. This means they should remain reliable even after 5,000 plug and unplug cycles.

Charger Ports

There are two categories of charger ports that support USB-C: assured capacity ports and shared capacity ports. Assured ports can provide their specified amount of power regardless of how other ports are being used. In contrast, shared capacity ports distribute power among connected devices, which may result in lower power output when multiple devices are in use.

usbc port

On the left side there is a cluster of assured ports. Each of these ports reliably delivers its specified wattage, irrespective of the status of other ports in use. On the right side, there’s a group of three shared capacity ports with a combined wattage capacity of 60 watts. This arrangement means that if the two lower ports are already in use, the top port would only have 6 watts available for output when used concurrently.

Conclusion

As USB technology continues to evolve, it opens up new possibilities for faster data transfer, higher power delivery, and more versatile connections. USB4 and the USB-C Type 2.1 connector are at the forefront of this innovation, driving the future of connectivity for various devices.