Beware of cheap USB Type-C cables, warns Google engineer

The introduction of USB Type-C cables and devices is ushering in a new age of convenience, but it seems that not all cables are created equal. While it might be tempting to purchase a cheaper adapter cable to connect up your new gadgets, Google Engineer Benson Leung has been testing a few of them and has found that many aren’t actually suitable for use with his Chromebook Pixel laptop.

One of the important features with USB Type-C and 3.1 is support for 3A charging currents and this is where a number of budget cables are failing to match the standard’s specifications. Worryingly, this can be quite dangerous to hardware, as legacy devices may not be able to handle the charging currents when using adapter cables.

For example, when connecting up to an older USB 2.0 Micro-B charger with a Type-C adapter, the cable is supposed to provide a 56kΩ pull up resistor to the Vbus connector pin so that the host device correctly identifies the connected charger as a legacy device to lower the charging current to 1.5A or 2.4A. If you are using the USB cable for charging, the missing resistor could result in devices drawing more current from older chargers or hubs than they can handle, which clearly isn’t good.

Leung has found that a number of cables supplied on Amazon are missing this resistor or using 10kΩ instead, and therefore can’t charge up his Pixel laptop correctly. He has posted a series of reviews on a number of cables and also has instructions to help Pixel owners test their own cables.

If you’re concerned about this, your best bet is probably to stick with cables from reputable retailers. Adapters from FREiEQ, Belkin and iOrange all pass the test, or you can always use cables provided by your device manufacturer to ensure the correct support.