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by exmadscientist 11 days ago
> And if USB-C could somehow provide a range of voltages to the motherboard, SFFPC's could be downsized even more

You reeeeeeally don't want to do that. Cable inductance is a big deal, among other issues. You want the main DC-DC regulators on the board, usually right at the load, for the main loads. Most of the PSU bulk is for dealing with mains itself: handling 50/60Hz or mains isolation is just physically large. Getting in secondary 20V DC (or so) from a single connector and then regulating it down on board is pretty much the ideal solution.

(I can't even begin to comprehend the horrors of a USB-PD negotiation involving multiple voltages. It's already the worst standard I've ever had to deal with.* Don't make it worse!)

(* Not hyperbole, it is truly, truly awful. At least things like 60601 are bad because, you know, they're covering lots of stuff like lifesaving medical devices. USB-PD is... holy hell, it is just bad.)

2 comments

> I can't even begin to comprehend the horrors of a USB-PD negotiation involving multiple voltages. It's already the worst standard I've ever had to deal with.

Yeah but usually you don't have to deal with that yourself but have some sort of chipset that handles all the USB-C PD and, optionally, even data-lane muxing stuff.

I quite like PD 2.0 when ignoring the legacy USB-A stuff. It's semi-elegant. 3.0 and further made it an abomination though.