Legacy USB Type-C Charging Cables Dangerous?

DataPro News > Technical Info
November 19, 2015
Legacy USB Type-C Charging Cables Dangerous?

Some legacy USB-C charging cables could potentially cause damage to outdated USB charging hardware.

As reported across the web, OnePlus' USB Type-C to A cable and adapter are among many legacy USB Type-C cables and adapters that incorrectly identify themselves as capable of 3A fast charging. Google's Benson Leung is to thank for testing these cables and leaving detailed technical reviews on Amazon. By our count, Benson has found around 80% of legacy USB Type-C adapters tested so far have failed to comply with the USB 3.1 specification.

The Problem

Cables with this particular defect could cause trouble when you try to use the new USB Type-C "fast charging" capability with incompatible charging hardware. It is an unlikely but possible set of circumstances:

  • First, you'll need a device that will try to draw up to 3A while charging over USB Type-C: either the Nexus 5X, Nexus 6P or the Chromebook Pixel.
  • Next, you'll need a USB Type-C to Type A or B connector that identifies itself as capable of 3A fast charging by using a 10Ω resistor (this should never be the case with USB Type A & B!)
  • Finally, get the oldest, lowest quality USB hub or charging device you can find.

When you connect your new fast charging device with an out-of-spec cable to a USB charging port that can't hanlde 3A, at the very least, your device won't charge properly. Worst case, you'll fry the outdated USB port.

The Solution

According to the spec, all legacy USB Type-C connectors should use a 56Ω resistor which signals to your device that the power source can provide "Default USB Power" as opposed to USB Type-C fast charging. In the process of developing our new lineup of USB Type-C cables, we always make sure that our cables comply with the USB spec and are safe for you to use.

Check out DataPro's USB-C 3.1 adapters and read more about USB Type-C!