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USB 3.0 Connectors and Receptacles Explained

The other day, I opened one of the products I received for review, and I found a blue connector on the board with no description. USB 3.0 connectors are blue this connection seemed “funny” with two internal connectors, and I though it must have been something else, and asked on Google+.

Mele_X1000_USB3It turned out this is a USB 3.0 Standard-B receptacle. As my knowledge about USB 3.0 connectors was obviously lacking, I’ve decided to investigate and have a look at the different existing and upcoming USB 3.0 connectors that we should find in different types of devices and computers now or very soon.

Standard-A USB 3.0 connectors and receptacles

This is the easy one, it looks very similar to the USB 2.0 connectors, except it’s blue and adds 5 pins for USB 3.0 connectivity. It’s backward compatible with USB 2.0, and the receptacle is used for hosts. Most people must have already seen that one.


USB 3.0 Type A Connector and Receptacle

Standard-B USB 3.0 connectors and receptacles

USB 3.0 Standard-B receptacles and connectors are somewhat similar to the USB 2.0 version, but are larger, and with one extra row for USB 3.0 connectivity. Such receptacle accepts either a USB 3.0 Standard-B plug or a USB 2.0 Standard-B plug, and  it’s also backward compatible with USB 2.0. Due to different size, a USB 3.0 Standard-B connector can’t be plug into a USB 2.0 Standard-B receptacle. The Standard-B receptacle is used for USB devices. If you have a USB 3.0 device (e.g. USB hard drive) you must have already seen this, but since I don’t have ny it was my first time to see this type of connector.

USB 3.0 Type B Connector

USB 3.0 Type B Connector

Micro-A USB3.0 receptacle and Micro-B USB 3.0 connectors

The USB 3.0 Micro-B cable plug consists of a standard Micro-B USB plug, with an additional 5-pin plug place on the other side. That’s been done this way for USB 3.0 Micro-A host connectors to preserved compatibility with USB 1.x/2.0 Micro USB cables. There’s no way to connect a micro USB 3.0 cable into a micro USB 2.0 receptacle due to obvious mechanical differences. I understand these types of connectors and receptacles can’t be found in many devices just yet, Samsung Galaxy Note 3 being an example, but many mobile devices may eventually feature micro-B USB 3.0 receptacles.

Micro B Connector

Micro B Connector

micro_USB_3.0USB 3.0 Type-C

There’s a new type of USB 3.0 connector coming up announced last December. I could not find pictures yet, but we do know this new connector will be about the size of USB 2.0 Micro-B, it will be reversible (“users will no longer need to be concerned with plug orientation/cable direction”), support scalable power charging, and USB 3.1 Superspeed+. Since many people do not really like USB 3.0 Micro-B, USB Type-C connectors may even replace the latter in mobile devices such as tablets and smartphones.

USB 3.0 Signals

USB 2.0 has 4 signals: Ground, Power (5V), and D-/D+ differential pair for data. There’s also the shield provided by the metal housing. USB 3.0 is backward compatible but adds Superspeed transmitter and receiver differential pairs (4-pin), and ground for signal return. According to the table below, there are also some “Powered-B” with 2 extra pins for power and ground provided by the device.

USB 3.0 Pinout

USB 3.0 Pinout

Source: Mostly Wikipedia

  1. anon
    March 25th, 2014 at 16:18 | #1

    Hopefully the USB Type-C connector will be sturdier than the USB 2.0 Micro-[a|b|ab] connector, and as it is pretty much an clone of Apple’s Lightning port connector, it should be pretty much fool-proof. 😉

    And of course become the next de-facto standard for charging and host/device (OTG) functionality (too bad not including Displayport signaling for DisplayDock support)… EU better update their standard(s) demands.

    Just too bad it will take another painful transition between different cables, just like the mess with Mini and Micro changes. 🙁

  2. Paul
    March 25th, 2014 at 19:24 | #2


    > Just too bad it will take another painful transition

    So, maybe EU won’t update their demands for USB3 bloat, and will pass other demands, like that a device boasting USB2 support should offer end-user speed of 480Mbit/s +/- 20%. Oh, that would be quite an innovation kick-in-ass for the lazy hardware crowd.

  3. Dan
    March 25th, 2014 at 23:59 | #3

    The type A are incredibly flimsy, I’ve seen the connectors break off from the PCB on some devices.

    For some insane reason USB hard drives continue to use type A even when type B would be no problem to use.

    Hopefully type C fixes the problem.

  4. Rand
    March 30th, 2014 at 14:29 | #4

    the USB3 micro B connect on the side labelled usb 2.0 looks like a micro USB2 could you connect with a micro usb cable .. (at usb2 speeds)

  5. March 31st, 2014 at 08:34 | #5

    Yes, a micro-A USB3 connector will accept a micro-B USB 2 plug.

  6. April 2nd, 2014 at 22:01 | #6
  7. August 13th, 2014 at 11:57 | #7

    Reversible Type C specification released (http://www.usb.org/press/USB_Type-C_Specification_Announcement_Final.pdf)
    Key characteristics of the USB Type-C connector include:
    • Entirely new design
    o Tailored for emerging product designs
    o Robust enough for laptops and tablets; slim enough
    for mobile phones
    o Similar to size of USB 2.0 Micro-B
    •Usability enhancements
    o Reversible plug orientation and cable direction
    •Supports scalable power charging
    •Future scalability
    o Designed to support future USB performance needs
    •Mechanical specs:
    o Receptacle opening: ~8.4mm x ~2.6mm
    o Durability: 10,000 cycles
    o Improved EMI- and RFI-mitigation features
    o Power delivery capacity: 3A for standard cables and 5A for connectors

  8. PLAYER 1
    August 3rd, 2015 at 06:46 | #9

    Hello guys, mi external hdd 3.0 B has its 2.0 side dead, not broken , could i bridge the data lines to the 3.0 side of the conector??


  9. August 3rd, 2015 at 09:12 | #10

    @PLAYER 1
    It might be feasible since USB 3.0 is compatible with USB 2.0, and you can see the USB 2.0 signal in the table in the post above.

    But why don’t you just connect the USB 3.0 port to the USB 2.0 port of your computer / device with a USB cable?

  10. PLAYER 1
    August 4th, 2015 at 13:33 | #11

    If you have a 3.0 “only” device like i mentioned above, it wont comunicate with a 2.0 only input in any way, cause that device is not sending any 2.0 signal via 2.0 pins. Tested.

    You know that 3.0 and 2.0 data channels are different and dont share any point of hardware after the data processor.
    But i suppose the data is still present on both “hardwares”, so …

    The only possible way i imagine to solve that question is to try a bridge of data chanels.

    The other possibility is: if 3.0 side doesnt detect a 3.0 input it could shoot down that part of the output and continue sending data via 2.0 side…

    Ill try it for sure when i have a time
    Ill be back…

    (sorry for my bad english, i speak spanish)

  1. March 25th, 2014 at 18:49 | #1
  2. August 13th, 2014 at 14:50 | #2