Today it was announced by the USB-IF (USB Implementers Forum) that the latest USB connector which we first caught a glimpse of in April has been finalized, and with this specification many of the issues with USB as a connector should be corrected. USB, or Universal Serial Bus, has been with us for a long time now, with the standard first being adopted in 1996. At the time, it seemed very fast at up to 12 Mbps, and the connector form factor was not an issue on the large desktop PCs of the day, but over the years, the specifications for USB have been updated several times, and the connectors have also been updated to fit new form factor devices.

In the early ‘90s, when USB was first being developed, the designers had no idea just how universal it would become. The first connectors, USB-A and USB-B, were not only massive in size, but the connection itself was only ever intended to provide power at a low draw of 100 mA. As USB evolved, those limitations were some of the first to go.

First, the mini connectors were introduced, which, at approximately 3 mm x 7 mm, were significantly smaller than the original connector, but other than the smaller size they didn’t correct every issue with the initial connectors. For instance, they still had a connector which had to be oriented a certain way in order to be plugged in. As some people know, it can take several tries to get a USB cable to connect, and has resulted in more than a few jokes being made about it. The smaller size did allow USB to be used on a much different class of device than the original connector, with widespread adoption of the mini connectors on everything from digital cameras to Harmony remotes to PDAs of the day.

USB Cables and Connectors - Image Source Viljo Viitanen

In January 2007, the Micro-USB connector was announced by the USB-IF, and with this change, USB now had the opportunity to become ubiquitous on smartphones and other such devices. Not only was the connector smaller and thinner, but the maximum charging rate was increased to up to 1.8 A for pins 1 and 5. The connection is also rated for at least 10,000 connect-disconnect cycles, which is much higher than the original USB specification of 1,500 cycles, and 5,000 for the Mini specification. However once again, the Micro-USB connector did not solve every issue with USB as a connector. Again, the cable was not reversible, so the cable must be oriented in the proper direction prior to insertion, and with USB 3.0 being standardized in 2008, the Micro connector could not support USB 3.0 speeds, and therefore a USB 3.0 Micro-B connector was created. While just as thin as the standard connector, it adds an additional five pins beside the standard pins making it a very wide connection.

With that history behind us, we can take a look at the changes which were finalized for the latest connector type. There are a lot of changes coming, with some excellent enhancements:

  • Completely new design but with backwards compatibility
  • Similar to the size of USB 2.0 Micro-B (standard Smartphone charging cable)
  • Slim enough for mobile devices, but robust enough for laptops and tablets
  • Reversible plug orientation for ease of connection
  • Scalable power charging with connectors being able to supply up to 5 A and cables supporting 3 A for up to 100 watts of power
  • Designed for future USB performance requirements
  • Certified for USB 3.1 data rates (10 Gbps)
  • Receptacle opening: ~8.4 mm x ~2.6 mm
  • Durability of 10,000 connect-disconnect cycles
  • Improved EMI and RFI mitigation features

With this new design, existing devices won’t be able to mate using the new cables, so for that reason the USB-IF has defined passive cables which will allow older devices to connect to the new connector, or newer devices to connect to the older connectors for backwards compatibility. With the ubiquity of USB, this is clearly important.

There will be a lot of use cases for the new connector, which should only help cement USB as an ongoing standard. 10 Gbps transfer rates should help ensure that the transfer is not bottlenecked by USB, and with the high current draw being specified by connectors, USB may now replace the charging ports on many laptops as well as some tablets that use it now. The feature that will be most helpful to all users though is the reversible plug, which will finally do away with the somewhat annoying connection that has to be done today.

As this is a standard that is just now finalized, it will be some time before we see it in production devcies, but with the universal nature of USB, you can expect it to be very prevalent in upcoming technology in the near future.


Source: USB-IF

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  • mkozakewich - Thursday, August 14, 2014 - link

    I honestly expected that to be part of the article!

    I am disappoint.
  • sheh - Wednesday, August 13, 2014 - link

    Good, it's about time. I always felt having just 4 common plug variants is too few.

    Once they finish finalizing USB-C mini and USB-C micro I hope now they can start work on symmetric HDMI, HDMI mini, HDMI micro, DisplayPort, DisplayPort mini, DisplayPort micro. Maybe add symmetric HDMI-B too, just in case it ends up being used.
  • Lord of the Bored - Wednesday, August 13, 2014 - link

    I don't think it's really fair to call the USB-A and USB-B connectors "massive." I think we've kind of forgotten what it was LIKE in the old days.

    Yes, they're massive next to a microUSB connector, but... they were so much TINIER than the serial and parallel connectors they replaced! Yes, even the "small" 9-pin serial ports.

    And they LOCKED IN when you inserted them! No more fidgeting with thumbscrews or worrying the cable would fall off if you didn't.

    And they... okay, you still couldn't easily insert them blind, but no one's perfect.

    Anyways, I'm just sayin'... they aren't THAT big.
  • Brett Howse - Wednesday, August 13, 2014 - link

    Ha yes I suppose calling them massive isn't very fair when you look at their age :) But compared to the latest spec, it's a rather big connector for two power and two data lines, especially when it only supported 100 mA on the power lines. But to be fair - 18 years ago was a long time in the tech space.
  • mkozakewich - Thursday, August 14, 2014 - link

    I think they're smaller than HDMI connectors, too. I mean, really, it's surprising how well they held up all this time. Those were some amazingly slim connectors.
  • RU482 - Wednesday, August 13, 2014 - link

    "The first connectors, USB-A and USB-B, were not only massive in size, "

    lol, somebody doesn't remember plugging printers into 25 pin parallel ports. USB A and B were relatively tiny when introduced!
  • OreoCookie - Wednesday, August 13, 2014 - link

    Or external SCSI plugs … :-D
  • Peeping Tom - Wednesday, August 13, 2014 - link

    lol....damn those screws!
  • EvanAdams - Wednesday, August 13, 2014 - link

    I am so happy about Type-C. I hate hate hate USB-Micro. I hate at night and in the dark in bed having to figure out which side is up. Having it be flippable will just make my day.The sooner the better
  • GTRagnarok - Wednesday, August 13, 2014 - link

    When can we expect devices to adopt this?

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