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In the search for the "one USB Type C cable for everything", it looks like we are not quite there just yet. I'm looking for a Type C cable that can do Thunderbolt 3, USB 3.1 Gen 2, and 5A power delivery, of length up to 2 metres. We have 2m USB Type C fully-featured cables capable of 5A power delivery (and presumably USB 3.1 Gen 2 data transfer) but incapable of being used as a Thunberbolt 3 cable, and also 2m active Thunderbolt 3 cables capable of 5A power delivery but, as a USB Type C cable, unable to have anything more than USB 2.0 data transfer.
According to some sources, a 2m active Thunderbolt 3 cable that is cable of 5A power delivery but only USB 2.0 data transfer breaks the spec, yet Thunderbolt 3 cables manufactured by CalDigit and Cable Matters are USB-IF certified. I'm wondering two things:
- Is the above assertion, that a Thunderbolt 3 cable supporting only USB 2.0 data transfer, really breaking spec? If so, how did it receive USB-IF certification?
- Is it even possible to have a full-speed active Thunderbolt 3 cable capable of USB 3.1 (Gen 1 or Gen 2) data transfer when used as a USB cable? I'm getting the impression that the reason why no such cable (at least with 5A power delivery) currently exists is due to either the limitations of the active circuitry or the USB Type C spec itself (i..e. the cable doesn't have enough wires to support both).
Kelvin Chung
Posted 2017-07-06T03:05:41.930
Reputation: 119
You're specifically looking for 5A @ 20V = 100W power delivery, right? – Spiff – 2017-07-06T03:52:49.350
40Gbps-rated 2m "active" Thunderbolt 3 cables support both Thunderbolt 3 and USB 3.1 Gen 2 "SuperSpeed+" 10Gbps operation, by definition. If you look at the details when Thunderbolt 3 is claimed to be 40Gbps, you'll see that it's only 40Gbps when you combine Thunderbolt 3 mode on one set of high-speed pairs, plus USB 3.1 Gen 2 "SuperSpeed+" on the other set of high-speed pairs. This makes sense as Thunderbolt 3's main mode is to do PCIe Gen 3 x4, which is slightly over 30Gbps, so it needs SS+ to reach 10Gbps. So you're looking for a 2m active Thunderbolt 3 40Gbps cable that supports 100W PD. – Spiff – 2017-07-06T03:55:07.137
The Belkin 2m active 40Gbps Thunderbolt 3 cable that Apple sells almost works, but only seems to support 60W of PD (3A @ 20V, presumably). – Spiff – 2017-07-06T03:55:36.050
This is probably a question for someone who knows the cable spec and negotiation details better than I do. I think @AliChen is our local expert. – Spiff – 2017-07-06T04:08:08.777