USB-IF announced USB4 V2 in Oct 2022 as the next generation USB streaming standard. EU specifies, starting from 2024, USB Type-C connector will be the only charging port for cell phones and other portable products. For the demands in the European market, all those firms that did not support Type-C port are forced to adopt Type-C port as the interface for charging and data transmission. The expectations in the market indicate that this major change will lead to significant growth in number of products equipped with USB Type-C port.
The burst of high-density streaming needs over entertainment platforms encourages the improvement of transmission rates in data centers and peripherals to cope with data transmission needs. That’s why USB-IF upgraded USB4, which has been launched for 4 years, to V2. The noticeable change is the doubled transmission rate to 80 Gb/s. Without changing cable, connector and PCB design, USB4 V2 is the first USB communications standard adopting pulse-amplified modulation. The excessive signal attenuation for PAM-2 transmission in the old physical design makes it difficult to deal with transmission losses through IC compensation; the eye height of PAM-4 is merely 1/3 of the traditional NRZ 1/3, making it relatively difficult for deemphasis at the receiving end; and the tolerance to noises is unsatisfactorily low. For this, PAM-3 is selected to support data streaming at 25.6 Gbaud/s considering the Signal-to-Noise-and-Distortion Ratio (SNDR), thus realizing twice as much data transmission for every clock cycle and doubled bandwidth without boosting signal frequency. Without boosting signal frequency, the signal transmission distance is less susceptible to attenuation, which permits the use of existing physical design as usual. Using the tertiary encoding of PAM-3 for transmission, USB4 V2 extends the date rate from 25.6 GBaud/s to 40.22 Gbps, and dual -channel transmission is incorporated for ultrahigh speed transmission at 80Gbps. Figure 1 provides the USB4 V2 logo.
Figure 1 USB4 V2 Logo
USB4 V2 brings all other transmission interfaces together using high-speed connection, and fulfills the needs for data transmission, HD audio and video feeds, and fast charging. With host chips on PC and NB products, the needs in peripherals, such as USB hub and docking, are likely to take off. The good evaluations of USB in early days came from user experience; in particular, the plug-and-play feature and good compatibility are the key factors contributing its long-term use. The needs of general consumers for the speed to access external storage applications will accelerate the growth of the next generation USB4. For example, the access time will be drastically reduced, if USB4 V2 is adopted in external hard drives or NAS. In addition, the design of laptops and tablets today is all about compact size and streamlined, slick style, which is to say the support for other interfaces is limited. Corporate users often have to use docking to connect USB4 V2 to expand the transmission needs, such as HDMI, VGA and LAN, which is another opportunity for USB4 V2.
Seeing the design bottleneck coming from 80Gbps signals, Amazing Microelectronics developed AZ5B0S-01F, a single-channel TVS with merely 0.18pF of parasitic capacitance (Figure 2). It keeps signal integrity from impedance mutation along the transmission route. The PAM-3 eye height is half of the NRZ transmission, requiring more cautious noise tolerance. The small package of DFN0603P2Y provides better flexibility for PCB layout (Figure 3), and keeps the cross-talking below an acceptable level. The AZ5B0S-01F has an operating voltage of 2.0V, allowing for DP output in USB Type-C alt mode. The clamping voltage is only 5.5V with the bombardment of electrostatic gun at 8V, making the device a reliable electrostatic protection with good signal quality.
Figure 2 Type-C ESD/EOS Solution Parameters
Figure 3 USB4 V2 Type-C ESD/EOS Solution Layout
Also, most clients prefer the VBUS =20V design thanks to the support of Type-C for power delivery (PD). However, misalignment is frequent as the mechanism becomes loose over time due to Type-C plugging and unplugging. It is not unheard of that products are returned for repair as VBUS made contacts accidentally with neighboring CC and SBU. That’s why a lot of manufacturers specified in-house 20V short-circuiting test in order to prevent the repair of burned products. For a TVS that operates on 5V to prevent 20VDC from burning the products, Amazing Microelectronics developed the AZ5H25-01B with Vrwm =5V and Vbr =26.5V. No accidental action occurred during the 20V short circuiting test, effectively reducing the probability of burned TVSs.
The Type-C USB2.0 is one the interfaces with the highest repair rate. It is proven in the market that higher TVS的Ipp value in TVS helps reduce the repair rate. With this in mind, Amazing Microelectronics launches the AZ5515-02F to improve the Ipp to 11A. The dual-channel package of DFN1006P3X is incorporated to provide better protection, while satisfying customers with the need for compact design. When it comes to VBUS protection solutions, Amazing Microelectronics recommends AZ4524-01F, as its Ipp is as high as 50A, which is more than enough to protect against the surges due to power plugging or unplugging, or power fluctuation.
Amazing Microelectronics has the best-fit solution and protection suggestions based on years of market experience for signal cables and VBUS for USB4 V2 Type-C. Amazing Microelectronics will continue the efforts in the development of next generation protection devices, and believes we are up to the clients’ new needs and challenges in the increasingly evolving high-speed signal development.