An Engineer's Guide to USB Typе-С (2024)

(ti.com)

231 points | by gregsadetsky 6 days ago

10 comments

  • kubb 3 hours ago
    My new iPhone with USB C charging is such an improvement!

    Thank goodness for the European Union. If it weren't for them, we'd all be stuck with these flimsy Apple charging cables forever.

    • leokennis 1 hour ago
      Even if Lightning was possibly a nicer or smaller connector; nothing beats a true industry standard. Makes the entire “what chargers and cables to bring to connect my stuff” question so much easier.
    • BLanen 2 hours ago
      There were non-apple lightning cables already.

      And I have to say, the lightning connector itself is better than the usb-c connect in my opinion. I get that having the pins on the male* plug is a theoretical advantage in durability but that has not been my experience with usb-c connector durability on either end.

      EDIT: usb-c has pins on the male plug. Which is what I meant. So female -> male.

      • gwbas1c 1 hour ago
        > the lightning connector itself is better than the usb-c connect in my opinion. I get that having the pins on the male* plug is a theoretical advantage in durability but that has not been my experience with usb-c connector durability on either end.

        I always end up picking a lot of dust out of my usb-c ports on my phones; or otherwise the port wears out and disconnects before charging completes. (Right after my wife entered the hospital in labor, I needed to scrounge around for something to clean out my phone's port because the "go" bag only had a wired charger and my phone wouldn't charge on it.)

        It's why I went to a wireless charger for daily use.

        ---

        I'm real curious why lightning never became the standard. Was Apple trying to keep it proprietary? Was there a half-hearted attempt to open it up or otherwise convince the Android ecosystem to use it?

      • graemep 45 minutes ago
        I have not used lightning but I have found USB C to be much more fragile than USB A, although better than mini and micro. I would really rather have had evey thing be a few mm bigger and stick with A.
      • valina-line 2 hours ago
        That's fascinating; I've only had positive experience with USB-C cables and terrible with Lightning. What kind of cables do you commonly use?
      • kubb 1 hour ago
        Couldn't be further from my experience. They would always eventually stop connecting.

        I didn't mention the single cable for everything advantage, that goes without saying.

      • kotaKat 1 hour ago
        I've also had basically zero issue with Lightning connectors, but had a constant battle with USB-C of every kind to figure out what's charging, what's data, what's PD, and so much more hassle.

        I don't get why Apple was forced to colonize by the EU when they had the market-leading connector in place for significantly longer than USB-C even existed.

        "It's only USB2!" Does it have to support the faster USB3 speeds? Not really... we don't have to keep forcing everything to include the latest kitchen sink support.

        • Aefiam 39 minutes ago
          As far as I understand Apple could have still supported an additional lightning port if they really cared about it.

          Per gemini for making ligthning accessories you also have to pay 4$ to apple per device that are passed onto the consumer.

          I dont know in what way that has to do with colonization.

          USB everywhere is nice because you can use the same charger for all kind of devices and dont have to carry multiple with you.

          The different kind of specs for usb cables is unfortunate, but you can just buy the highest spec ones and only use them.

  • rjh29 5 hours ago
    Pretty good summary. It can be confusing since type C is "just a connector" but it's pretty heavily coupled with the protocol now.
  • imtringued 4 hours ago
    Guides like this explain why there are so many broken USB-C devices. The guide mentions that you do not need a PD chip for 5Vs, but then tells you that USB C is a cold connector meaning 0V is on VBUS when nothing is connected and jumps straight into the complexities of the PD protocol running over the CC pins instead of explaining how to get the 5V without the PD chip first.

    Then in the section where it tells you how to do that, it fails to properly explain how to connect a load switch (10 cent component at 100 units) to get around the 10uF limit. The vast majority of applications will require less than 15 W and a good chunk of them can't get away with 10uF between VBUS and GND so a schematic how to do it in the lowest cost way would have helped here.

    Edit: After reading until the very end I got the impression that this is just an ad for Texas Instruments PD controllers.

    • crote 4 hours ago
      Basic 5V devices just need a 5.1k resistor on each CC pin to GND. It is pretty obvious when reading the actual USB-C Connector Specification.
    • mapt 2 hours ago
      My phone's USB-C port is worn out, and so now it's a brick if I don't have a wireless charging dock around.

      Is it physically impossible to get bandwidth and power out of something as durable as a Magsafe connector, even a larger-scale version?

      • __mharrison__ 56 minutes ago
        I generally stick magnetic USB C connectors into things like keyboards, phones, and iPads.

        The slight bulge is worth the reduction in insertions. Also is very convenient for snapping when I need to connect.

    • dvh 4 hours ago
      Now I want to know, how to add larger than 10uF cap?
      • freeone3000 13 minutes ago
        Why? 10uF is already pretty beastly, and the point is to dampen signal verses intermittent drops and drains, not power the backing device for any amount of time.
  • wolfi1 7 hours ago
    there is a timestamp as parameter, I don't know, what it is good for, but the link works without it as well
    • account42 6 hours ago
      Might be for cache busting.
      • wolfi1 6 hours ago
        could be, but for pdf documents I would assume that they are not changing this much
        • crote 4 hours ago
          TI usually links to chip datasheets, which do tend to change from time to time. Having both a reference to a specific revision and a trivial link to the latest revision is quite handy in practice.
        • Lex-2008 4 hours ago
          timestamp corresponds to Oct 08 2025, so probably the last time the file was modified
  • delis-thumbs-7e 7 hours ago
    Nice one. I need to read this later.
  • ahk-dev 5 hours ago
    USB-C reminds me of HTTP: one familiar interface hiding an enormous amount of complexity underneath.

    That's great for experts, but difficult for everyone else because the same connector can expose wildly different capabilities depending on the implementation.

  • elhart05 4 hours ago
    The EPR safety design is the part worth highlighting for anyone not deep in USB PD. The handshake is deliberately structured so a single message error can't accidentally push a port into a 100W plus contract, the sink has to actively drive entry into EPR mode and the source verifies cable capability before sourcing anything above 20V. That's a sensible failsafe given how much heat and current you're dealing with at 48V and 5A. The eUSB2 section is also underrated context for why this matters beyond cables. As process nodes shrink below 7nm, the old 3.3V USB 2.0 signaling literally becomes a reliability risk to the silicon itself, which is why chipmakers had to invent a whole lower voltage PHY just to keep USB 2.0 alive on modern nodes.
  • qwertox 10 hours ago
    Good find!
  • faangguyindia 6 hours ago
    I use an Apple Silicon Mac and often use programmable keyboards like the Royal Kludge RK61 via USB C. when I press keys such as A, S, D, F, W, or nearby keys in quick succession, the keyboard stops responding completely until I unplug and reconnect it. I've even replaced the USB C cable with a new store bought cable, but the issue still persists.
    • DaSHacka 5 hours ago
      Check if your keyboard has a way to enable n-key rollover (NKRO)

      https://en.wikipedia.org/wiki/Key_rollover

      • faangguyindia 4 hours ago
        You are genius! thanks this completely solved my issue, for those curious https://postimg.cc/75hV9tCK

        I use usevia, all i had to do was find a keyboard definition file for my keyboard which claude found in 2 minutes!

    • rjh29 5 hours ago
      Usb isn't the issue, you bought an extremely budget mechanical keyboard.
      • thenthenthen 5 hours ago
        Also avoid Epomaker, had the same issues, but needed a full reflash (every other day), losing all my layers etc. (The import function was broken lol)
      • faangguyindia 4 hours ago
        turns out it was just me not knowing my keyboard has full qmk support and can be configured via usevia, what N-key rollover (NKRO) is.

        my keyboard is actually r65 by royal kludge i got that wrong!

        I was gifted this keyboard and i just love its feel.