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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  • SirKnobsworth - Wednesday, August 13, 2014 - link

    Have they released the pinout yet? I only count 12 pins, which doesn't seem that future-proof given that USB 3 is already 9.
  • UpSpin - Wednesday, August 13, 2014 - link

    More pins doesn't make a serial bus faster!
    The big difference between USB2 and USB3 was the switch from half duplex to full duplex.
    Of course they could stuff another lane (4 additional pins, then you have more or less the layout of Thunderbolt) in the USB bus to double the speed, but I rather expect they want to keep the pin count low to keep the connector simple and the cable thin and flexible. They'll reather improve the protocol, signal analysis, frequency, ... to further increase transfer speeds.
  • SirKnobsworth - Wednesday, August 13, 2014 - link

    Yes, I know it will only use 9 pins for the foreseeable future but one of the justifications foe the new connector was some level of future-proofing.
  • repoman27 - Wednesday, August 13, 2014 - link

    I'm actually fairly impressed this time around. There's D+,D- and Vbus for legacy USB 2.0 functionality, control and sideband use channels, Vconn for powering electronically marked or active cables or accessories, and 4 differential pairs, only two of which are currently used for SuperSpeed or SuperSpeedPlus implementations. The minimum power rating for Type-C cables is 5 V, 3 A, which is much more realistic for the types of applications people expect to use USB for nowadays. There's even a set of pin assignments built into the spec to support an analog audio mode.
  • edzieba - Wednesday, August 13, 2014 - link

    12 pins per side for 24 total, assigned dynamically ('upper' pins separate from 'lower' pins, uper and lower determined by handshaking) for USB3.1 and statically ('upper' pins mirror 'lower' pins) for USB 3.0 and below.
  • repoman27 - Wednesday, August 13, 2014 - link

    Full pinout an details are available here:

    The site seems to be getting hammered with all the news today, so it took me quite a few attempts to actually download the entire zip.
  • SirKnobsworth - Wednesday, August 13, 2014 - link

    Thanks. It looks like they're going with full configurability here - the interface can be adapted to a variety of different use cases - it even has enough configurable pins to support DisplayPort/DockPort or dare I say ... Thunderbolt even. Of course, trying to enable many signaling modes on the same port comes with its own problems, but this opens up some very interesting possibilities!
  • R3MF - Wednesday, August 13, 2014 - link

    If they really have kept backwards compatibility with USB 2.0 i hope they have found a more elegant solution than keeping parallel pins as was the case with USB 3.0.

    tell me this is so?

    it would be a terrible waste in what is supposed to be a compact streamlined plug format for micro devices!
  • V-600 - Wednesday, August 13, 2014 - link

    In the third paragraph shouldn't "As some people know, it can take several tries to get a USB cable to connect..." actually say it can take 2 tries to connect?
  • Brett Howse - Wednesday, August 13, 2014 - link

    You've clearly not heard of USB Superposition

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