AN-001 · APPLICATION NOTE

The charging cable that will not carry video

You plug a laptop into a USB-C monitor with the cable that came with a phone charger. The laptop charges. The screen stays black. Nothing anywhere reports an error, because as far as both devices are concerned, nothing is wrong.

Why it happens

A USB-C cable does not have to wire all of its pins. The cheapest and most common class, what we call the drawer cable, wires the power pair and the USB 2.0 data pair and simply omits the four SuperSpeed lanes. DisplayPort alt mode, the mechanism that carries video over USB-C, travels exclusively on those SuperSpeed lanes. No lanes, no video, no matter what the ports support.

There is no rule that the cable must warn you. The connector is identical, the charge negotiation succeeds, and the display path silently never comes up. Vendors sell this class with 240 W ratings printed on the box, which makes it look premium; wattage and data are independent axes.

What to buy instead

Any full-featured USB-C cable carries video: the 5 Gbps class is the cheapest that does. If you also want charging above 60 W in the same cable, you need the 5 A e-marked variant. When in doubt, a Thunderbolt 4 universal cable does everything every time; see the cable matrix.