With different standards and charging technologies at work, it’s much harder than it should be to figure out what a cable can do. There are a few things worth knowing when shopping.
USB standards: The Universal Serial Bus (USB) standard dates back to 1996, but has undergone many new standards, revisions, and connector types in the years since. Instead of going through them all here, we’re trying to emphasize what’s important.
Connectors: Fortunately, while USB-C is becoming a standard connection type, you’ll want cables with connectors that match your existing devices. Today, that can still mean USB-A, Lightning, or even MicroUSB. Remember that the capabilities of any cable are limited to the oldest connection type.
Facts: The data transfer rate is always in megabits per second (Mbps) or gigabits per second (Gbps). You know what speed a cable should be able to reach as standard:
- USB 2.0 supports 480Mbps
- USB 3.0 supports 5 Gbps
- USB 3.1 supports 10 Gbps
- USB 3.2 Gen 1 supports 5 Gbps
- USB 3.2 Gen 2 supports 10 Gbps
- USB 3.2 Gen 3 supports 20 Gbps
- USB 4.0 supports 40Gbps
Current: While cable manufacturers always state the maximum charging speed, your device determines how much power it should consume, so it’s important to know what standards it supports and pair your cable with the correct power adapter. The charging speed of a cable is measured in Watts (W). Sometimes manufacturers state specifications on the cable in small print. If no W is listed, you can calculate it by multiplying the voltage (V) and the current (A), assuming they are listed.
USB-A ports are limited to 12 watts. USB-C ports can go up to 240 watts (they used to be limited to 100W), but it depends on the device. For example, USB-C typically supplies 18 watts to a phone. Apple’s Lightning ports can work with USB-A or USB-C cables.
Thunderbolt was a proprietary interface developed by Intel and Apple, but is now open for royalty-free use (still certified by Intel). With Thunderbolt 3, the standard adopted the USB-C connector and is capable of data transfer rates of up to 40 Gbps and can deliver 100 watts of power using the PD standard. Thunderbolt 4 brings several improvements mainly related to the video signal (support for two 4K displays or one 8K display). It also supports the USB 4 standard and is backwards compatible with previous standards. We plan to test Thunderbolt and USB 4 cables in the coming weeks.
The Power Delivery (PD) standard is as close as possible to a common standard. A few manufacturers, such as OnePlus, Oppo and Xiaomi, still have their own charging standards. Then there’s Qualcomm’s Quick Charge (QC) standard, which has been the most popular for phones for years, although Quick Charge supports 4+ PD. Even PD has a variant called Programmable Power Supply (PPS), which is part of the USB PD 3.0 standard. PPS allows real-time adjustments to maximize efficiency and charge phones like the Samsung Galaxy S22 series at up to 45W instead of the usual 18W.
Cable Certification: There are a few different types of cable certification. When a cable is certified, it usually means that it has been independently tested and meets specific standards. As a buyer, it gives you peace of mind that your cable will perform as the manufacturer claims. Certification can be expensive, so many cable manufacturers shy away from it, but that doesn’t necessarily mean their cables are of poor quality. The USB Implementers Forum (USB-IF) is a non-profit organization dedicated to advancing USB technology. Run by members such as Apple, Google, HP, Microsoft and Intel, it sets specifications and offers certification. If a cable is certified by the USB-IF, it has been tested to ensure it meets the standards. Apple has its own Made for iPhone (MFi) certification for Lightning cables.