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I am looking to power homebrew computer designs with USB-C. I have previously used USB-B micro at 5v and the current limits there haven't been a problem but when building analog circuitry (a sound card for example) being restricted to 5V single-supply op-amps is limiting. So I have been investigating the feasibility of using USB PD with the following requirements:

  • Sink only, this computer will never source, only sink current
  • USB 2.0 data transfer. I want a single port (USB-C) connected to a host computer for power and usb-to-serial data over D+/D- so data must go both ways
  • higher voltage so I can create a more reasonable dual-supply (+- 10V from 20V maybe? Ideally +- 12V from 24V but I don't believe this is officially part of the PD spec.)
  • current shouldn't be a problem, I don't think I will get close to 3A

According to this Texas Instruments primer on USB-C this should be possible. See header "USB Type-C DRP/DRD: USB 2.0 with USB PD". But in searching for an IC to do PD negotation for me, I don't ever see references to D+/D- in conjunction with PD.

So my question is are there example circuits for this kind of scenario? Are there good ICs for PD negotation and/or USB 2.0 data transfer? I looked at the barrel-jack replacement series (CYPD3177) which is used in decoy boards a lot but those are always for power, never data transfer but if the two concepts are separate, I would love to know about it.

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  • \$\begingroup\$ Welcome! If power is sufficient, have you considered DC/DC converter(s) to generate your needed voltage rails? It would simplify things for your end users to be able to use standard USB 2 as it. \$\endgroup\$
    – winny
    Oct 4, 2023 at 8:27
  • \$\begingroup\$ You would be stuck plugging your device into a USB PD supply rather than normal USB . If you're ok with an external power brick, skip USB PD and get a wall wart with a barrel connector. Much easier and far less confusing. If you aren't, generate higher voltages from USB+5 \$\endgroup\$ Oct 4, 2023 at 12:50

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You can buy USB-C PD decoy modules that trigger out voltages higher than 5V from e.g. power supply.

However, if you are going to plug your device into a standard PC or laptop with Type-C port, do not expect it to output more than 5V. They are not needed to do that. There may be some models that do or there will maybe be such PCs in the future. And it will definitely prevent using it with older PCs that don't have Type-C natively as they can only connect via adapter cable so no support for more than 5V and also you don't know how many PCs with Type-C don't give out more than 5V even if they accept 20V in.

Maybe think about using two separate ports for data and power supply - they both can be Type-C though.

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