Brief explanation of TYPE-C interface specification requirements

TYPE-C interface has been widely used in electronic industry. I believe no one can tell exactly how many USB ports exist in the world. Analysts say that it is estimated that at least 2 billion devices with USB ports are shipped every year, which can be said to be quite amazing. "The previous USB interface was square, but the new Type-C interface was round, and the outside became smoother and simpler." Brad Saunders, chairman of USB-IF, introduced the advantages of the Type-C interface, saying that it is also more convenient to use, and you can plug it forward or backward. When plugging in, you can hear a&＃39; click&＃39; sound, which means there is no problem with the access.

Looking back at the development history of USB, when the USB 1.0 specification was first established in 1996, it was actually difficult to attract the favor of peripherals and device manufacturers, because the USB 1.0 specification only defined the transmission speed of 1.5 Mbps, and it was difficult to achieve the efficiency required by users in data communication. At that time, Fast SCSI had been able to support the range of 10 Mbps. Even at that time, the IEEE 1394a transmission interface of another Heat （Apple computer called Firewire） had a transmission speed as high as 400 Mbps. So in order to enhance competitiveness, Intel introduced USB 2.0 HS（High Speed） in 2000, and the transmission rate was increased to 480 Mbps.

USB released the specification of USB 3.0 in 2008, and the transmission speed is as high as 5 Gbps. In the era of USB 3.0, it is called SS（Super Speed）. Since its launch, USB 3.0 has become the most popular mainstream interface, and it has been fully used in various external markets, such as external hard disks, solid state hard disks （SSD）, DVD players and so on.

Facing the challenge of other high-speed interfaces, in 2013, USB also introduced a new specification of USB 3.1, which supports transmission speed up to 10 Gbps, and changed its name to USB 3.1 Super Speed Gen 2, while USB 3.0, which originally supported 5 Gbps, was called USB 3.1 Super Speed Gen 1.

TYPE-C interface specification was announced in August 2014. Although it was included in the specification of USB 3.1, in fact, Type-C still has the specification of USB 2.0. The following are the four characteristics of Type C:

1. Smaller size: similar to the existing USB 2.0 Mirco-B in size.

2. Power charging: Type-C will support higher power charging capability.

3. Extensibility: The design of Type-C will support the performance of USB in the future.

4. Usability: Both sides can be inserted, so users will no longer need to distinguish between front and back, and it is easier to insert the interface.

The size of the final version of Type C is about 8.4mm x 2.6mm, which is slightly larger than the Micro-B of USB 2.0. Its charging capacity itself supports 15W, and it also supports USB Power Delivery specification, which will support the power supply capacity up to 100W. In terms of transmission speed, in addition to supporting the existing 10 Gbps of USB 3.1 Super Speed Gen 2, it is also expected to support subsequent higher transmission speeds （such as USB 4）. In use, it supports the plug-in of the front and back （such as the Lightning interface of Apple computer）, and can be expanded to be suitable for thin portable devices such as tablet computers and smart phones, so it is particularly expected by the market. Why Type-C is so popular is closely related to its characteristics. It can carry out high-speed data transmission, power charging and video data transmission, and has an all-in-one function. Moreover, Type-C can provide small, "reversible pluggable" connectors and bidirectional cables with better user experience.

The connector design of TYPE-C interface is very different from the previous USB connector, which adopts the type of terminals in both upper and lower rows. There is only one type of board-end connector, which is designed with 24 terminals. On the interface of the board end connector, there are Vertical, Right Angel, Mid-Mount and other forms. The forms of terminal pins are also Dual-Row SMT, Hybrid and so on. On the other hand, there are two designs of Plug on the line, namely, Full Featured version and USB 2.0 version which support high transmission speed. Because Type-C is designed for upper and lower rows of terminals, because in cable processing, the Paddle Card connection must be made at the end of the Plug, and the core wire is processed on the Paddle Card. At the same time, the association also defined that if the Type-C cable wants to support the power supply capacity of more than 3A, it must have USB Type-C Electronically Marked for annotation. In the part of cable specifications, there are mainly the following three items:

1. standard Type-C cable

2. Traditional USB cable

3. Traditional USB converter

Among the standard Type-C cables, there are two specifications: USB Full Featured Type-C cable and USB 2.0 Type-C cable.

In the traditional USB cable, there are two specifications: USB 3.1 and USB 2.0. The USB 3.1 specification defines three types: USB Type-C to USB 3.1 A cable, USB Type-C to USB 3.1 B cable and USB Type-C to USB 3.1 Micro-B cable. The USB 2.0 specification defines four types: USB Type-C to USB 2.0 A cable, USB Type-C to USB 2.0 B cable, USB Type-C to USB 2.0 Mini-B cable and USB Type-C to USB 2.0 Micro-B cable.

There are two kinds of traditional USB converters: USB type-c to USB 3.1 receiver and USB type-c to USB 2.0 micro-b receiver.

In terms of test specifications, the test of Type-C has the following main requirements:

1. Structural test: Type-C is mainly used in handheld devices, so it needs to be plugged and unplugged for 10,000 times like USB Micro-B. The insertion force and pull-out force are also different from those of other original USB types. The pull-in force of Type-C is 5~20N, and the pull-out force is 8~20N. At the same time, cable bending test and cable pull-out test must be carried out. Like Micro-B, Type-C must also carry out 4-axis test.

2. Electrical test: The test of low-order rated resistance （LLCR） has also changed, and the initial value has changed from 30mΩ to 40mΩ. In addition, Type-C must be tested for current temperature rise, with a current of 5A at the Vbus terminal and a current of 1.25A at the Vconn terminal, and the temperature change cannot exceed 30oC.

3. Environmental test: The requirements are the same as those of USB 3.0, and the environmental test is run according to EIA 364-1000.01.

4. Electroplating requirements: same as USB 3.0 requirements.

5. High-frequency test: The biggest difference between the specification of Type-C and the previous USB specification is that Type-C also defines a series of high-frequency test requirements for board-end connectors. The high-frequency test requirements of Type-C board-end connectors and standard Type-C cables are shown in Table 2 （the test requirements of traditional USB cables are different）.

TYPE-C interface is just an interface, which can support USB3.1, 3.0 and 2.0 standards at the same time. The maximum speed that can be supported at present is 10Gbps, and 20Gbps will be supported in the future. Therefore, using the Type-C interface does not mean that your transmission speed is 10Gbps, but it may be 480Mbps supported by USB2.0. To achieve the highest transmission speed is also related to the cable selected. "If the USB2.0 standard is used, the longest cable is generally about 5 m. If the USB3.0 is used, the USB cable cannot be longer than 3m to achieve the speed of 10Gbps.