The USB Implementers Forum (USB-IF) introduced USB4 version 2.0 in fall 2022, and it expects systems and devices with the tech to emerge later this year and into next year. These upcoming products will largely rely on Intel’s Barlow Ridge controller, a full-featured Thunderbolt 5 controller that goes above and beond the baseline USB4 v2 spec. And though extremely capable, Intel’s Thunderbolt controllers are also quite expensive, and Barlow Ridge isn’t expected to be any different. Fortunately, for system and device vendors that just need a basic USB4 v2 solution, ASMedia is also working on its own USB4 v2 controller.
At Computex 2024, ASMedia demonstrated a prototype of its upcoming USB4 v2 physical interface (PHY), which will support USB4 v2’s new Gen 4 (160Gbps) data rates and the associated PAM-3 signal encoding. The prototype was implemented using an FPGA, as the company yet has to tape out the completed controller.
Ultimately, the purpose of showing off a FPGA-based PHY at Computex was to allow ASMedia to demonstrate their current PHY design. With the shift to PAM-3 encoding for USB4 v2, ASMedia (and the rest of the USB ecosystem) must develop significantly more complex controllers – and there’s no part of that more critical than a solid and reliable PHY design.
As part of their demonstration, ASMedia had a classic eye diagram display. The eye diagram demoed has a clear opening in the center, which is indicative of good signal integrity, as the larger the eye opening, the less distortion and noise in the signal. The horizontal width of the eye opening represents the time window in which the signal can be sampled correctly, so the relatively narrow horizontal spread of the eye opening suggests that there is minimal jitter, meaning the signal transitions are consistent and predictable. Finally, the vertical height of the eye opening indicates the signal amplitude and the rather tall eye opening suggests a higher signal-to-noise ratio (SNR), meaning that the signal is strong compared to any noise present.
ASMedia itself is one of the major suppliers for discrete USB controllers, so the availability of ASMedia’s USB4 v2 chip is crucial for adoption of the standard in general. While Intel will spearhead the industry with their Barlow Ridge Thunderbolt 5/USB4 v2 controller, ASMedia’s controller is poised to end up in a far larger range of devices. So the importance of the company’s USB4 v2 PHY demo is hard to overstate.
Demos aside, ASMedia is hoping to tape the chip out soon. If all goes well, the company expects their first USB4 v2 controllers to hit the market some time in the second half of 2025.
