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Inphi PAM4 PHY Aims at Systems

September 26, 2017

Author: Bob Wheeler

Inphi is reentering the system-side-PHY market after having focused on optical modules over the past few years. The new Vega design builds on the 16nm Polaris family that sampled in 1Q17, adding autonegotiation and forward-error-correction (FEC) options for various port speeds up to 400Gbps. Supporting both 56Gbps PAM4 and 28Gbps NRZ, Vega can retime one 400G Ethernet port or act as an NRZ-to-PAM4 gearbox for a 200G Ethernet port. It also handles 50G and 100G Ethernet including draft 802.3cd.

Vega’s DSP-based equalization works with high-loss channels, making it well suited to both front-panel and backplane applications. In the former case, it connects a switch chip or packet processor to an optical module such as QSFP56 for 200GbE as well as QSFP-DD and OSFP for 400GbE. The chip handles front-panel ports employing direct-attach cabling (DAC) as well as optical media. For backplanes, it supports the 200GBase-KR4 draft standard.

The new design comes to market as switch chips that offer 200GbE and 400GbE approach sampling. They include a 12.8Tbps chip from Innovium and a 6.4Tbps chip from Mellanox. Simple 1U switch designs shouldn’t require retimers between the switch chip and optical module, but larger modular systems will require retimers. These new Innovium and Mellanox offerings should reach production in 2H18, setting up 2019 as the year 200GbE and 400GbE port shipments ramp to volume.

Inphi isn’t new to system-side PHYs, having acquired 10Gbps PHYs through Cortina in 2014. It skipped the 28Gbps NRZ generation, however, and is reentering with 56Gbps PAM4. This move renews Inphi’s competition with Broadcom in system designs, pitting it against the data-center switch-ASSP leader. Broadcom is sampling 16nm PHYs similar to Vega, offering separate devices that target front-panel or backplane designs. Inphi can serve OEMs using custom ASICs, however, and is already working with Innovium.

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