While PAM4 suffers from ~9.5dB SNR compared to NRZ, it has a huge advantage when inspecting insertion loss. The reason PAM4 gets traction in higher frequencies is the channel loss. 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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