What is USB Type-C?

 Sep 1, 2021   |    George Lui

USB 3.0 Now is USB 3.2 Gen 1X1

In terms of transfer rates, for perspective, the USB 1.0 specification introduced in 1996 offered a maximum data transfer rate of 12 Megabits per second (Mbps). USB 2.0 maxes out at 480 Mbps. However, USB 3.0, 3.1, and 3.2 can be confusing to the user. Let’s break it down.

USB version Issue Date Marketing Term Bits/Sec Power Delivery USB Symbol Port/Cable symbol USB Charging symbol
USB 1.0 Jan 1996 Low Speed 1.5 Mbps 5V/500mA Blog_USB_1_Port
USB 1.1 Aug 1998 Full Speed with Updated 1.5 Mbps/12 Mbps 5V/500mA Blog_USB_1_Port
USB 2.0 April 2000 High Speed 480 Mbps 2.5W (Max) Blog_USB_2 Blog_USB_1_Port
USB 3.2 Gen1x1
(was USB 3.0)
Nov 2008 SuperSpeed USB 5Gbps 5Gbps 4.5W (Max)
USB 3.2 Gen2x1
(was USB 3.1)
July 2013 SuperSpeed USB 10Gbps 10Gbps 100W (Max)
USB 3.2 Gen2x2
(was USB 3.2)
Sep 2017 SuperSpeed USB 20Gbps 20Gbps 100W (Max), USB Type-C connector Only
USB4 Gen 2x2
(was USB 4)
Sep 2019 USB4 20Gbps 20Gbps 100W (Max), USB Type-C connector Only
USB4 Gen 3x2
(was USB 4)
Sep 2019 USB4 40Gbps 40Gbps 100W (Max), USB Type-C connector Only

Table (1) USB specification summary

The USB 3.2 specification replaces the USB 3.x specification and introduces a new nomenclature. USB 3.2 defines the following connection speeds:

  • USB 3.2 Gen 1: Originally known as USB 3.0, and previously renamed to USB 3.1 Gen 1. It’s the original USB 3.0 specification, and it can transfer data at up to 5 Gbps.
  • USB 3.2 Gen 2: Previously known as USB 3.1, and then later as USB 3.1 Gen 2. It offers speeds of up to 10 Gbps.
  • USB 3.2 Gen 2x2: Formally known as USB 3.2, it’s the newest spec, promising speeds at up to 20 Gbps (by using two lanes of 10 Gbps).

The USB 3.2 protocol specification only defines the performance capabilities that may be implemented in a product; USB 3.2 is not USB Type-C, USB Standard-A, Micro-USB, or any other USB cable or connector and USB 3.2 is not USB Power Delivery or USB Battery Charging.

Figure-1
Figure (1) USB connectors

What is USB Type-C?

In the past, USB only transmitted data; however, the Type-C connector is designed to contain the data, power, and video transmission. Let’s take a look at what functions USB Type-C supports.

Power Delivery

The latest power delivery specification is PD3.0. The major difference between PD2.0 and PD3.0 is Programmable Power Suppliers (PPS) mode; many different devices might be plugged into a given PD charger, but PD is universal. Thus, the PPS approach demands that the sink side be smarter for fast charging, and also be compatible with QC 3.0/4.0/4.0+; MTK Pump Express (PE) 2.0/3.0; and Samsung Adaptive Fast Charging (AFC).

Charging Technology USB PD 3.0 QC4+/4/3.0 Samsung
Output Voltage 5V~20V 3-21V 5V/9V
3.6-20V
3.6-20V
Output Current 5A max (Via EMCA) 2.6A/4.6A 2A/5A
3A(PD)/4.7-5.6A
3A(PD)/4.7-5.6A
Step Size 20mV 20mV /
20mV
200mV
Maximum Power 100W 100W 45W
USB PD27W
Protocol USB PD Quick Charge Adapting Fast Charging USB PD 3.0
USB PD3.0 Compatible

Table (2) Power Delivery Specifications

Another important feature of PD 3.0 technology is Fast Role Swap (FRS), where a device that is providing power can quickly change its power role from the Sink to Source and the Hub dual-role port starts sinking power. The USB accessory flash drive and monitor continue functioning during the FRS event; FRS helps to prevent any data loss that may occur when the Hub upstream facing port (UFP) power is unexpectedly removed from a device. FRS improved the data loss inherent in PD 2.0.

Here are important PD features:

  • Bidirectional power capability
    USB-C is a bidirectional port, featuring a variable input and 5V to 20V output voltage range. Its adjustable output voltage allows devices to use USB-C to replace the conventional AC/DC power adapter and USB-A and B terminals.

  • Electronically Marked Cable Assemblies (EMCA)/E-Marker
    Inside of the USB-C cable, an E-Marker carries all Type-C signals, and functions as an integrated circuit used to process the Power Delivery communication protocols. The electronic marking allows for role switching, alternate mode selection, and power protocol control between source and sink to supply power up to a maximum of 100W.
    When USB type-C to type-C cable supports 3A electric current or above, the E-Marker chip is a mandatory; E-Marker is also required for USB-C full-featured (Active) cable.

    Figure-2
    Figure (2) VIA Labs’ E-Marker for USB Type-C Cable


  • Max. 100W power delivery
    After the USB-C cable has been identified as an EMCA by a device, the USB PD Bi-phase Mark Coded (BMC) communications allocate one of the five USB-C power delivery profiles to the CC1/CC2 wire. Power delivery, up to a maximum of 100W, then starts.
  • Billboard
    An error notification through Billboard devices is shown in Figure (3), which demonstrates a Billboard message from a Binary Device Object Store (BOS) descriptor.

    Figure-3
    Figure (3) USB Type-C Billboard function

Data Transmit

The USB-C connector is available at both ends or at just one end of the cable for the specifications below:

  • USB 3.2Gen 1x1
    Product capability: product signals at 5 Gbps
    Marketing name: SuperSpeed USB

  • USB 3.2Gen 2x1
    Product capability: product signals at 10 Gbps
    Marketing name: SuperSpeed USB 10 Gbps

    The USB-C connector will be used at both ends of the cable for the specifications below:
  • USB 3.2 Gen 2x2
    Product capability: product signals at 20 Gbps
    Marketing name: SuperSpeed USB 20 Gbps

  • USB 4 Gen 2x2 and Gen 3x2
    40G (20 Gbps x2) 20 Gbps USB4 (Gen 2x2) and 40 Gbps USB4 (Gen 3, 20 Gbps x2)

You can use an USB Type-C male to USB A type female adapter to connect an existing product; nevertheless, you will remain at the existing data speed or even lower due to the insertion loss occur between the adapter and cable. For example: If an old USB external hard drive uses USB A/M to USB Micro B/M cable, data speed may be lower. Use a USB 3.1 Cable - Type C Male to USB 3.2 Gen2x1 Micro B cable instead of a Type-C adapter to ensure full-speed data transmission.

A/V

  • Alt Mode enables the USB-C to carry non-USB signals; the DisplayPort Alt Mode allows a USB-C equipped computer/cell phone to connect the monitor directly via USB-C.

  • VESA DisplayPort Alt Mode Standard Version v2.0 was released on April 29, 2020. In DisplayPort Alternate mode, the video signal transmits via (2) Display Port lanes or (4) Display Port lanes (e.g.: DP0-DP3 to RX2; TX2; TX1; RX1). At DP 2.0 single display, the maximum resolution supports 8K 60Hz, 4:4:4, including 30 bits per pixel (bpp) for HDR-10. Figure (4) shows a USB-C connector PHY switch supporting DP Alt mode.

    Figure-4
    Figure (4) Alt Mode connection 4-Lane DP flip in source side


    DP Alternate Modes in AV functions include:
    • DisplayPort
    • Thunderbolt
    • MHL

  • HDMI Alternate Mode supports the HDMI 1.4b spec (4K30, 4K60 4:2:0), ARC, HEC, CEC, Deep Color, and a few other HDMI-specific features; but, it cannot support simultaneous USB 3.1 or USB 2.0 data in any configuration.

  • MHL Alternate Mode for USB Type-C launched in 2015 by MHL Consortium; although, a few MHL Alternate Mode consumer hardware devices have been distributed into the market.

Know Your USB Type-C Devices

USB Type-C has multiple functions; yet, your device may not include the full USB type-C functions.

The USB-IF, VESA, and Intel defined the logo usage guidelines to explain the USB-C technology inside.

1. USB Type-C with video output function

  1. USB3.2 Gen1x1 Type-C + Display, with video display function, and theoretical bandwidth with a maximum transfer rate up to 5 Gbps.

    Figure-5
    Figure (5) USB3.2 Gen1x1 Type-C + Display logo


  2. USB3.2 Gen2x1 Type-C + Display, with video display function, and theoretical bandwidth with a maximum transfer rate of up to 10 Gbps.

    Figure-6
    Figure (6) USB3.2 Gen2x1 Type-C + Display logo


  3. When you find a lightning symbol next to the USB-C interface, that means Thunderbolt technology is inside. Thunderbolt combines PCIExpress and DisplayPort technology, which can simultaneously transmit both data and video signals up to 40 Gbps bandwidth.

    Figure-7
    Figure (7) Thunderbolt logo

2. USB Type-C without video output

  1. USB3.2 Gen1x1 Type-C theoretical bandwidth with a maximum 5 Gbps transfer rate.

    Figure-8
    Figure (8) USB3.2 Type-C 5 Gbps logo


  2. USB3.2 Gen2x1 Type-C theoretical bandwidth with a maximum 10 Gbps transfer rate.

    Figure-9
    Figure (9) USB3.2 Type-C 10 Gbps logo


  3. USB 10 Gbps Trident Logo + MHL Logo

    Figure-10
    Figure (10) USB 10 Gbps + MHL Logo

3. USB Type-C with power delivery

If you see the trident is enclosed in a battery shape, it means the USB-C connector enables power delivery (PD).
Below is an example of a USB3.2 Gen1x1 Type-C + PD. with charging function, 5 Gbps maximum transmission speed.

Figure-11
Figure (11)

The USB Type-C charging logo next to the type C connector means the port can be power charged.

Figure-12
Figure (12)

4. USB Type-C interface without any logo

Figure-13
Figure (13)

Not all devices include a symbol on the product to help you identify the USB-C technology inside. A USB-C interface is common in MacBook and Chromebook computers. Usually, the USB-C interface supports charging and data transfer, and provides video signal output; but, we still recommend reading your product spec sheet to know your device’s USB-C features.

Conclusion

USB-Type C only describes the physical connector. USB Type-C is not the same thing as USB 3.2 or USB 3.1, so knowing the Type-C technology inside your source devices is important.

USB-Type C offers data transfer, power charges devices, and transmits video. All of these functions are performed by just one cable. For the cable to bear a maximum of 20 volts at 5 amps (100 W) power, it is important to use a quality USB-Type C cable.

USB4 will be available only for USB-C ports. USB4 Type-C will support Thunderbolt 3/4 and also includes a PCIe function. More USB4 devices will be launched in 2021, so you may see USB4 Type-C devices on your desk and in your backpack very soon.

Additional Resources

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About the Author

George Liu

Product Engineer

George Liu has 12 years’ experience in the cabling, data, and video connectivity industry. As a Project and Product Manager at Black Box, he works directly with domestic and international OEM suppliers on new product launches. George is a certified PMP and CQE, and he is a master’s candidate in the industrial management program at National Taiwan University of Science and Technology.