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Given a USB cable which supports power delivery, does it necessarily support PD 3.0 and QC 3.0? (And only need to power source and device to support these protocols?)

Do I need to check anything other than the maximal wattage it allows to see if it supports either one?

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  • \$\begingroup\$ @jay - Hi, Sorry, that's another edit which makes things worse :-( For example, you changed it to say: "Do I need to support these protocols?" No! The question is about the cable and whether that will support use of PD 3.0 and QC 3.0 - not a person or anything else that "I" could refer to. Also garbled the grammar to say "is it necessarily to support" :-( I'm rolling back the edit... (Please note what I said in my last message on this topic.) Thanks. \$\endgroup\$
    – SamGibson
    Sep 7, 2021 at 0:03
  • \$\begingroup\$ @SamGibson , Sorry, I should stop doing that. :-) \$\endgroup\$
    – jay
    Sep 7, 2021 at 0:14

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No, they aren't.

First of all it's only a connector form factor. Which follows previous types A & B. It does not necessarily implement even USB at all. A cable with USB-C connector(s) might not be a full USB 3.1 cable. Some vendors sell cable with only Vusb & GND lines connected, so you definitely can't get any sort of fast charge out of them.

Contrary to that, a cable certified as USB 3.1+ cable should also meet USB Power Delivery 2.0 specs.

As for the QC - it's a proprietary specs & protocol which are outside of USB standards. As for those you should look for a cable technical parameters to see if it supports QC 3.0 or not. In fact QC 3.0 protocol doesn't needs those extra USB 3.0 lines and can work over USB 2.0 type of cables as it requires only D+/D- lines for negotiation. Cable should still meet the current ratings for those.

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To begin, Type-C connection standard explicitly prohibits the use of proprietary power delivery protocols such as QC. Since USB Type-C spec release 1.3:

4.6.2.3 Proprietary Power Source

This section has been deprecated. Devices with USB Type-C connectors shall only employ signaling methods defined in USB specifications

So the formal answer to first part of your question, no, "no USB Type-C cables support QC method". However, since QC uses USB2 wires, and every Type-C cable does have USB2 wires, every USB C-C cable can support QC-whatever, if someone is willing to violate USB Type-C specifications in their product.

Regarding the second part of this question, the cable communication channel is just a wire inside the cable, between two ends. So whatever PD mode is implemented in host and agreed by the device (link partner), it will be supported/negotiated. Again, SOP processors that are (must be) embedded into every C-C cable, will inform the host about cable capabilities, and PD firmware will restrict the power delivery accordingly. So technically you personally don't need to check anything, everything will be checked out by PD firmware in the USB host port.

If you mean by "checking" as a person developing the PD firmware for a USB host, you should know better.

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