USB-C is powerful but needs protection

USB-C is powerful but needs protection

The USB Type-C (USB-C) interface is rapidly unifying standards for charging and data transfer in electronic products.As the USB-IF continues to update the USB-C standard, it is becoming more and more powerful.

New challenges posed by new standards

At the beginning of the definition of the standard, the USB-IF is a "technologically forward-looking physical interface" such as the positioning of the USB-C.Facts also show that over the years, USB in the data transmission and power transmission standards behind the improvement, USB-C to provide strong support is not to blame.

Specifically, after years of iteration, the USB data transfer standard has been upgraded from USB 1.0's 1.5Mbps, USB 2.0's 480Mbps, to USB 4.0's 40Gbps. to be able to have this kind of backbone and iteration speed, and USB-C provides dual-channel (x2) architecture is not unrelated.

In terms of power transfer, USB-C supports up to 240W (48V @ 5A), a feature that makes it possible to greatly expand the range of devices that can be powered through the USB-C interface.Moreover, USB-C has a specially defined CC line for PD protocol transmission, which is responsible for negotiating the power protocol between the power supply and the powered device, which makes the realisation of Programmable Power Supply (PPS) possible and ensures that USB-C based fast charging can achieve higher energy efficiency.

It can be said that, compared with other interfaces, the USB-C physical interface standards and data transmission standards and USB PD power transmission standards support each other, synergistically promote the achievement of its mainstream status today.

However, "the greater the capacity, the greater the responsibility", USB-C in the data and power transmission on the ability to improve, but also brings new challenges, especially from the reliability and stability of the challenge.This is because these standards in the development did not directly provide for the protection of USB interfaces from external hazards of specific methods, and in practice, due to the USB-C smaller form factor, connection density is greater, in the interface of the circuit protection will face more pressure, especially in the electrostatic protection (ESD) and overheating protection of the two aspects, there must be a targeted programme to ensure that the reliability of the USB-C interface.

USB-C Protection

Circuit protection in the usual sense includes overcurrent protection and overvoltage protection. there are four different design architectures for USB Type-C overcurrent protection.

The first is the direct use of integrated power switch PD controller IC, this solution is more integrated, the performance is also the best, but the cost is also higher.

The second lower cost is the "PD controller + current sense circuit" scheme, but the performance is limited.

The other two solutions are "PD controller + external power switch" and "PD controller + MOSFET + PTC" with moderate cost.

The Four Circuit Protection Schematics are shown below:

The overvoltage protection aspect of USB Type-C is achieved through TVS. Due to the USB Type-C forward and reverse plug non-directional structure, it has the upper and lower two symmetrical interfaces, each group includes two groups of 10Gbps high-speed data transceiver channels (SSRX+/SSRX -, SSTX+/SSTX -), a group of compatibility with the previous USB standard 480Mbps data channel (D+/D-) and a group of USB-PD protocol communication dedicated channel (CC + / -), so the number of channels to be protected is also more than the previous USB interface, which requires TVS arrays. To this end, circuit protection component manufacturers have introduced miniaturised, highly integrated solutions.

For example, the solution shown below uses two 6-channel TVS arrays, CDDFN10-0516P columns, and a 4-channel TVS array, CDDFN10-0524P, to provide overvoltage protection for USB Type-C with only three devices.

In addition to over-voltage and over-current protection, new protection needs are gradually being identified, such as over-temperature protection. Due to the small size of USB Type-C, the pin spacing is small, and to carry up to 240W of power, so once the cable interface end of the foreign matter contamination, it is easy to cause an increase in internal resistance, which in turn triggers overheating or even the danger of fireworks. So the need to add over-temperature protection in the cable end is gradually being recognised, Japan's MCPC (Mobile Computing Promotion Consortium) has been involved in over-temperature protection provisions, I believe that the future of Europe and the United States and the Chinese market will also follow.

There are two common solutions for Type-C over-temperature protection:

One is the use of mini-Breaker temperature control device, which is a resettable device that triggers when the temperature is abnormal (too high) and self-recovers when the power is cut off or the temperature returns to a safe level;

The other option is to use a P-TCO, which is a temperature-triggered resettable fuse that is smaller in size compared to the mini-Breaker and is also more competitive in terms of cost.

With the accelerated popularity of USB Type-C interface, its powerful functions will be gradually revealed, and all kinds of creative products will come out one after another. While enjoying the powerful functionality of USB Type-C, consumers will also have greater demands for its reliability and safety, so we Hornmic will continue to focus on the quality and safety of the USB Cable, and wholeheartedly provide our customers with the most optimal and intelligent connection solutions.

By HornmicLink_Bob Kuo @230901 10:38