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USB data cable introduction (P2/2)

2020-5-27 17:14:34

For the different types of sockets and plugs described in 3.1, these 24 PINs and signals are not necessarily all used. For details, please refer to the USB Type-C specification. In addition, you may have noticed that among the USB Type-C 24 PIN signals,  Power class (GND / VBUS) and data class (D + / D- / TX / RX) are completely symmetrical (for Power, no matter how it is plugged in, it is the same; for the data line, simple routing, just  Can work).  The rest, including CC, SBU and VCONN, are used to detect direction, line type, etc.

Interpretation of Type-C Cable specification application

The USB2.0 series interface has been used for many years. The current mainstream market will gradually move to the Type-C interface. The current 2.0 series above will unify the final interface into the Type-C interface. The 2.0 series is mainly divided into data transmission + charging, 3.0  The series is mainly for data transmission + charging, and when it is finally unified to 3.1, it will be unified as: data transmission + charging + audio + video data line.

USB2.0 A TO C wiring and application products

Application: It is suitable for devices such as mobile phones and other USB Type-C interfaces to connect existing USB chargers and computer host USB interfaces for data transmission.

USB2.0 B TO C wiring and application products

Application: suitable for devices with USB2.0 square port interface such as printers, square port cameras, etc.

USB2.0 MINI TO C wiring and application products

Application: suitable for devices with USB2.0 mini interface such as game consoles, mobile hard drives, etc.

USB2.0 Micro B TO C wiring method and application products

Application: suitable for devices with USB2.0 micro B interface such as old mobile phones.

USB3.0 Micro B TO C wiring and application products

Application: suitable for mobile phones and hard drives with USB3.0 micro B interface devices.

USB3.1 connection method and application products

There are two types of USB3.1 cables: coaxial cable and twisted-pair cable. The actual number of twisted-pair cables is at least 16. On the basis of the twisted-pair cable, about 4 additional GND cables are needed  Realize the shielding of the coaxial line.

In the figure, A6 and A7 are USB2.0 data PIN, A8 and B8 are reserved Pin bits, A5 and B5 are configuration channels or power supply for active devices (you can detect whether the USB TYPE C connector port is mated, thus  Decide how to configure the power supplier, establish the master-slave relationship of the connection, detect the current size of the connection and control the power supply, and of course the most important USB PD communication to supply power to the active device, including the functional expansion required by the HUB, etc.).

The high rate adopted by the USB3.1 data standard has entered the microwave field. Transmission of such a high rate through connectors and cables must consider the distortion caused by the discontinuity of the channel. In order to maintain the degree of distortion at a controllable level, the standard  It specifies the impedance and return loss of cables and connector pairs.  The test items also include Impedance (Property Impedance), Propagation Delay (Propagation Delay), PropagationSkew (Transmission Delay), Attenuation (Attenuation), Crosstalk (crosstalk) and other test items.

USB3.1 bare wire products

As shown in the following table, the cable length of the USB2.0 specification is less than 4 meters, the length of USB3.2 Gen1 is less than 2 meters, and the cable length of USB3.2Gen2 is less than 1 meter.

Full function USB Type-C cable signal description

The following figure is the wire structure reference of USB3.1 pair twisted wire and coaxial wire!

The picture above is a standard USB Type-C cable. The high-speed signal differential pair SDP uses coaxial cable, and the signal ground return is through the shield GND.

USB2.0 / USB3.1 / USB3.2 cable description

As shown below, if the type-c cable is only used as a USB function, there are actually many signal lines that are not needed, and only the following signals are required (except for USB3.2 Gen2x2).  USB2.0 requires fewer cables, and its 5-10 signal is not needed.

Conductor wire gauge selection of cable

At present, the specification does not specify the specifications of the cable conductor. You can flexibly choose according to the factory's application customer group and equipment superiority, choose from the cost and use scenarios, flexibility, practicality of installation occasions, etc., multiple wires can be used for a single wire,  Such as Vbus or ground, it is recommended to use the smallest wire number to meet the requirements of cable assembly, electrical and mechanical, in order to maximize the flexibility of the cable, the outer diameter of the cable should be reduced as much as possible, a typical USB full function  The outer diameter of Type-C type cable can be from 4mm to 6mm, and the outer diameter of a typical USB2.0 Type-C cable can be from 2mm to 4mm, and the outer diameter of a typical USB Type-C USB3.1 cable can be from  3mm to 5mm, the wire number refers to the following table, and there are detailed explanations in the specifications:

Impedance control

The impedance of the SDP shielded differential line is controlled at 90Ω ± 5Ω, the single-ended coaxial line is controlled at 45Ω ± 3Ω, and the impedance is recommended to be evaluated with a rise time of 200 ps (10% -90%).

Introduction of important table parameters in association specifications

For more information about the USB Implementers Forum (USB-IF) or USB Type-C specifications, please visit or contact us

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