In this article, we won't get into the details of what one can learn from an eye diagram but will just say that the more open the eye and the less distortion, the better. Here's a 56G NRZ eye diagram measured on Cadence IP: In NRZ, the data stream 0010-0110-1110 would be coded as follows: NRZ typically uses less power than PAM4, avoiding the need for complex equalizations. It's easier to design and it has a ~9.5dB better signal-to-noise ratio (SNR) compared to PAM4. At 56Gbps, the Nyquist frequency would be 56G/2=28Ghz. NRZ is widely used in applications under 56G. The Non-Return-to-Zero (NRZ) method, which is also referred as Pulse-Amplitude Modulation 2-Level (PAM2), has two voltage levels representing logic "0" and logic "1". The next two paragraphs might be a bit technical, so if you don't need the background, please feel free to skip to the actual solution space. The high-compute cloud sector that constantly increases performance requirements, looking at 400G and far beyond.īut first, I wanted to touch on the two coding schemes that are widely used in designs today.PCI Express® (PCIe®) starting from legacy, moving into PCIe 4.0 with 16G, PCIe 5.0 with 32G, and as the spec evolves, PCIe 6.0 with 64G support. We're seeing a few trends that are driving the performance: Before diving into the various solutions, let's touch on the fundamentals. This article overviews the high-speed SerDes IP solutions available today.
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