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I have designed a MCU board using CYPD3177 USB-PD controller IC. The goal is to request 9V from a laptop and/or a PC computer's USB Type-C port whilst also establishing data communication. Current consumption is negligible, few tens of milliamps. Circuitry around CYPD3177 IC is identical to that presented in the datasheet.

The board works fine when connected to a fast charge adaptor, successfully negotiates 9 V. However, when connected to a computer's USB type-C port, it either fails to negotiate higher voltage and falls back to 5 V "safe power" (HP Probook 450 g6 - Thunderbolt 3/4) or fails to get any power whatsoever (Dell Vostro 5581 - USB 3.2 Superspeed with PD).

Both ports are capable of fast charging; they can charge a smartphone or similar devices without any problems. The board also works fine, as previously said, with a fast charge adaptor, or when the USB-PD controller IC is set such that it would request 5 V.

Is a PD-capable USB Type-C port of a laptop also capable of providing higher voltages, or is it limited to only 5 V with high currents? If the port is capable of providing high voltages, why does my board fail to negotiate for them?

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    \$\begingroup\$ Are there any specifications available for the USB port of the exact model of laptop you're using? \$\endgroup\$ Sep 30, 2023 at 18:00
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    \$\begingroup\$ I suppose you could find out what IC the computer uses to supply power to the USB port and check its capabilities on its datasheet. If it only says 5 V then that is definitely all it's going to supply; anything else might depend on the optional presence of additional circuitry. \$\endgroup\$ Sep 30, 2023 at 18:22
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    \$\begingroup\$ Spec sheet or else hook up a PD device and poll the port to see what voltages it supports. That said, if you only need "negligible" current, it is a bad idea to depend on an optional voltage that most ports won't support. Instead, run off of 5v, skip PD entirely and generate your voltages on the device from 5v. \$\endgroup\$ Sep 30, 2023 at 18:47
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    \$\begingroup\$ I think this is a bad idea, but if you want an external power supply and it must be USB-C at 9v, then ship the device with an included power supply or hub that supports the specific voltage you need. Otherwise people are going to be very confused why the device doesn't work most of the time when they plug it in. \$\endgroup\$ Sep 30, 2023 at 19:36
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    \$\begingroup\$ They probably don't exist. Thunderbolt 3/4 certification requires at least 1 port source a minimum of 15 W, which is 5V 3A, so that's probably all you get. \$\endgroup\$
    – user71659
    Oct 3, 2023 at 2:57

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Assuming you've already got the boards and need to ship them as is, you can get hubs that split out the data from the USB-PD cheaply on Amazon:

https://www.amazon.com/Anker-PowerExpand-Ethernet-Delivery-MacBook/dp/B08C9HZ5YT

Then include whatever laptop you want.

If you haven't finalized your design yet, ditch the USB-PD as it is inappropriate for this application. PD lets you request higher voltage, but your application demands it, so it's incompatible with a large majority of USB ports.

Fortunately, if you really only need tens of milliamps, there are much better solutions. You can get a capacitive voltage doubler for half the price of the CYPD3177, which (for low current loads) will give you 10v from every USB port on Earth. Throw in an LDO and you've got a regulated 9v supply with lower noise then a USB rail and paid less for it.

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  • \$\begingroup\$ This was my first idea as well, and even if I was able to get 9 V out of the computer, I still would provide such device as a backup. However, I am confused with these devices, because they appear to be designed to provide high power to the computer, not another device. Most of these don't mention PD on the other type-c port, and some explicitly state that it doesn't support PD. Would it work if I were to plug the type-c cable that supposed to plug into computer to my device, and the other type-c port to the computer? \$\endgroup\$
    – aulven
    Oct 1, 2023 at 10:13
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    \$\begingroup\$ @aulven I'm not familiar with that specific hub (just an example of a powered hub where you could ensure 9v), but I think you could plug the host into any USBC port on it. If not, there's lots of other products, some even with multiple PD ports. \$\endgroup\$ Oct 1, 2023 at 13:39
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Is a PD-capable USB Type-C port of a laptop also capable of providing higher voltages?

Not necessarily, it depends on particular design. In most practical cases a Type-C laptop port is not designed to provide more than +5V default power, usually set to 3A. I have never seen a laptop that has a "charging port" capable of supplying elevated voltages, even on a monster-size "gaming laptops". The ports can take elevated voltages, but not supply.

Even then, when running on battery alone, the port might dynamically switch to 1.5A (or disable another USB-C port) if power management firmware determines that the system running power plus USB supplied power exceeds battery capability. If running with AC-DC adapter, the policy might be different. In any case it depends on design, and port capabilities should be clearly stated in device user manual.

And for your particular application your best bet is to use a pump-up converter as user1850479 suggested.

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