It feels like USB3 isn't popular yet, and USB4 is here!

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It feels like USB3 isn't popular yet, and USB4 is here! [Copy link]

An important indicator of the vitality of a technical standard is its iterative upgrade process. If a standard is "stopped", it means that it is not far from the end. USB ushered in another major version update in September last year - USB-IF officially released the USB4 specification, which means that this standard, which was born in 1996, has entered the "4" era.

The advantages of high speed, small size, unified standards, hot-swap support, and power transmission make USB the most widely used high-speed serial interface standard. It has even become the only external expansion interface in some products (such as Apple's MacBook Pro). So what is special about USB4 as a "new species" and what changes will it bring to the market and product development? Let's take a look today.

From USB 1.0 to USB4

The USB transmission protocol is a serial data transmission technology jointly developed by Compaq, DEC, IBM, Intel, Microsoft, NEC and Nortel in 1994, and the USB-IF has completed the standardization and market promotion work. In the past 20 years, it has undergone several important version updates.

The USB 1.0 specification was released by USB-IF in 1996, with a transfer rate of only 1.5 Mbps, which could only be considered an initial trial. The large-scale commercial use of USB actually began with the release of the USB 1.1 specification in September 1998, which increased the transfer rate to 12 Mbps and revised some technical details in USB 1.0, gaining wide market recognition and gradually becoming the standard configuration on computers, which were at their peak at the time.

Table 1: Overview of USB standard development

As users' appetites grew, speeding up became the only way for USB standards to go. The USB 2.0 standard introduced in April 2000 did not disappoint, with a transmission rate of 480Mbps, 40 times that of USB 1.1. This transmission standard has been used to this day and has become the longest-lived USB standard.

Eight years later (November 2008), USB ushered in the 3.0 era. The maximum transmission rate of USB3.0 jumped to 5.0Gbps, and it also supported full-duplex data transmission. It also increased the power transmission capacity from 5V/500mA before USB 2.0 to 5V/900mA, which was a comprehensive upgrade. Then, USB 3.1 was released in July 2013, which further increased the transmission speed to 10Gbps, and the maximum power supply was increased to 100W (20V/5A). It is worth mentioning that along with the upgrade of USB 3.0/3.1, there are also new USB Type-C interface specifications and upgraded USB-PD power transmission specifications. The combined efforts of these parties have contributed to the current trend of USB interfaces "dominating the world".

USB 3.2 was released in September 2017. Although it is not a major version update, it fully utilizes (and only supports) the characteristics of USB Type-C, supporting dual 10Gbps channels (x2) for a total of 20Gbps data transmission. This design idea actually became a prelude to the subsequent USB4.

Figure: The dual-channel (x2) data transmission method introduced in USB 3.2 laid the foundation for USB4 (Source: ON Semiconductor)

What's new with USB4

"Speeding up" is still the main theme of USB4. In terms of design, USB4 continues to use the USB Type-C dual-channel (x2) data transmission architecture verified by USB 3.2, but abandons the USB specification in the basic protocol and adopts the higher-speed Thunderbolt 3 specification provided free of charge by Intel to USB-IF. This move doubles the transmission performance of USB4 to 40Gbps, which is comparable to Thunderbolt 3!

However, behind the speed increase, there is another deeper meaning: from now on, the USB specification and the "Thunderbolt" standard have merged. "Thunderbolt" was originally a transmission standard jointly developed by Intel and Apple. Due to the high patent fees, its large-scale application was hindered. Intel opened Thunderbolt 3 to USB4 for free, and the direct impact was that USB4 added a new feature that is compatible with Thunderbolt 3 devices. In fact, this is also a fusion of the ecosystems of both parties, which will form a win-win situation in the long run.

In addition to being "fast", USB4 also has a very innovative design, which is to truly realize "one port for multiple uses". Through the tunneling protocol, USB4 can simultaneously support the transmission of multiple information such as data and video, and can dynamically allocate bandwidth resources. For example, if the transmission of 1080p video requires 20% of the bandwidth in the total bandwidth of 40Gbps, then the remaining 80% of the bandwidth can be used for data transmission at the same time. Although similar bandwidth resource allocation can also be achieved through the DisplayPort Alt mode in USB Type-C, the bandwidth division ratio is fixed at 50:50, and it is impossible to dynamically make full use of bandwidth resources. This feature will undoubtedly make the application of USB4 more diversified and accelerate the process of USB unifying the interface world.

In other aspects, since USB4 only supports USB Type-C, this will promote the market penetration and application upgrade of USB Type-C. In addition, in terms of compatibility, USB4 has announced that it is backward compatible with USB 3 and USB 2 specifications, so it can support most USB devices on the market. It can be seen that the overall structure of USB4 is still very meticulous.

Trends and influences

Of course, with the release of USB4, relevant players must also start to plan ahead and make preparations. In the short and medium term, everyone's focus and attention will focus on the following aspects:

• Such a high transmission rate will bring challenges to the corresponding circuit design. Many design factors that do not need to be worried about at medium and low frequencies (such as signal integrity) may become new problems. This requires developers to cultivate some new skills.

• Higher transmission rates will also place higher demands on connectors and cables, and corresponding product selection needs to be prepared in advance.

• The emergence of USB4 will also have an impact on related specifications such as USB Type-C and USB-PD, which need to be upgraded accordingly. Considering the changes in the evolution of standards, choosing some programmable controllers with upgradeable firmware should be a necessary consideration.

From experience, it takes about 18 months from the release of a new USB transmission standard to the birth of commercial products. It is expected that devices using USB4 will not be available until early 2021 at the earliest. Given that being a "pioneer" in new technologies is risky, most players will choose to pay close attention and wait for opportunities. However, the upgrade mode has been started after all, and it may be dangerous not to keep up with the pace.

Source: Avnet WeChat Official Account

wsmysyn

It's too fast. I haven't even played 3.1.

dcexpert

There used to be a wirelss USB, but it seems to have been forgotten now.

damiaa

It happened too fast, luckily all the small USB flash drives were broken.

led2015

Technology is always developing, and the technology is always improving, but unfortunately the quality will not be improved, which is heartbreaking.

led2015

damiaa posted on 2020-7-17 11:17 It was too fast, fortunately all the small USB flash drives were broken.

Because a USB flash drive cannot be used more than once, 3 will develop into 4 and then 5.