Understand the Power of USB Cables: Thunderbolt, e‑Mark and 240W Charging

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Why is it worth paying attention to USB cable specifications?

USB cables play an important role in everyday device usage, enabling charging, data transfer, and video transmission. Specifications like 240 W or 40 Gb/s define their actual capabilities and impact the comfort of working with devices. Below, we discuss the key parameters of modern USB-C cables.

240 W and 40 Gb/s USB-C cable - what makes this standard stand out?

What does 240 W mean?

The 2021 USB PD 3.1 standard increased the maximum charging power over USB-C from 100 W to 240 W. New fixed voltages were introduced: 28 V, 36 V, and 48 V, allowing for 140 W, 180 W, and 240 W, respectively, while maintaining a 5 A current (previously the limit was 100 W at 20 V and 5 A). Such power enables charging the most demanding devices, such as gaming laptops or mobile workstations, even under heavy loads. To charge at full power, the cable must be clearly marked as 240 W; a standard 100 W cable is not enough.

Fun fact: at 240 W, a USB-C cable operates at 48 V, which is four times higher than a car's 12 V electrical system.

40 Gb/s speed - how does it work in practice?

A bandwidth of 40 Gb/s enables ultra-fast file transfers, meaning copying large projects or video footage takes just a few seconds. This solution is particularly useful for video editors and graphic designers working with external SSDs. It is worth noting that a cable's charging power alone reveals nothing about its data speed. A high-power charging cable might only transfer data at basic USB 2.0 speeds unless the manufacturer equipped it with a faster controller.

Comparison of USB-C cable specifications

USB-C cable - 100 W and 20 Gb/s

Key features:

• Charging power: 100 W
• Data transfer: 20 Gb/s
• Video resolution: 4K@60Hz
• Extras: built-in e-Marker chip, durable connector housing, robust braiding.

Applications:

• Charging laptops, smartphones, and tablets requiring up to 100 W of power.
• Transferring files at speeds up to 2000-2500 MB/s.
• Stable connection to an external 4K monitor.

USB-C cable - 240 W and 40 Gb/s

Key features:

• Charging power: 240 W
• Data transfer: 40 Gb/s
• Video resolution: 8K@60Hz, 4K@120Hz
• Support for Thunderbolt 4 and USB4 protocols.

Applications:

• Powering gaming laptops and the most demanding workstations.
• Connecting ultra-high-resolution monitors or multiple displays simultaneously.
• Blazing-fast copying of large file libraries.

Features	100 W Cable	240 W Cable
Charging power	100 W	240 W
Data transfer	20 Gb/s	40 Gb/s
Resolution	4K@60Hz	8K@60Hz, 4K@120Hz
Compatibility	USB-C, Power Delivery	USB-C, Thunderbolt 4, USB4

What are e-Marker and Thunderbolt chips?

e-Marker chip - controlling power parameters

A USB-C cable without an e-Marker chip carries current up to 3 A, which limits the power to 60 W at 20 V. For 5 A operation (i.e. 100 W and higher), an e-Marker chip is required. This integrated circuit provides the charger with essential technical information about the cable, including its maximum rated current capacity.

Fun fact: the e-Marker chip is a small circuit inside the connector that tells the charger how much current the cable can handle.

• Communicates the cable's maximum supported parameters to the charger.
• Protects the connected device from operating with excessive current.
• Enables safe negotiation of Power Delivery profiles.

Thunderbolt 4 - versatility and high bandwidth

The Thunderbolt 4 standard has a bandwidth of 40 Gb/s and charges laptops requiring up to 100 W of power. Importantly, a Thunderbolt 4 cable also functions as a standard USB-C cable, ensuring full backward compatibility with older ports.

• Compatible with Apple hardware and Windows PCs.
• Enables simultaneous power delivery, fast data transfer, and high-resolution video output.

What to look for when choosing a USB-C cable?

Charging power and the e-Marker chip

For a smartphone, a standard cable up to 60 W is sufficient, but laptops and more powerful power stations require a 100 W or 240 W cable with an e-Marker chip. If a device requires more than 100 W of power, a USB PD 3.1 specification cable clearly labeled as 240 W is necessary.

Data transfer speed

Cables differ in their internal wiring. If you plan to regularly transfer large files between an external drive and a computer, choose a cable rated for 10 Gb/s, 20 Gb/s, or 40 Gb/s (USB4 / Thunderbolt 4). Basic cables bundled with chargers often limit transfer speeds to the USB 2.0 standard (480 Mb/s).

Video signal support

Not every USB-C cable can carry a video signal. To connect a monitor, you need a cable that supports DisplayPort over USB-C (DP Alt Mode) or the Thunderbolt 4 standard, providing sufficient bandwidth for 4K or 8K signals.

Length and build quality

Cables with tight nylon braiding and reinforced connectors are more resistant to bending and fraying. You should also consider cable length: for 40 Gb/s transfers, passive cables are typically up to 0.8 - 1 m long to maintain complete signal stability without interference.

Recommended 240 W USB-C and Thunderbolt cables

Sources

• USB-IF: USB Charger (USB Power Delivery) - manufacturer page (usb.org)
• Plugable: What Is 240W USB Extended Power Range (EPR)? - industry article (plugable.com)
• Plugable: What is an E-Marker and why do they matter for power delivery? - industry article (kb.plugable.com)
• Intel: What Is Thunderbolt 4? - industry article (intel.com)