Memory + Interfaces

56 Gbps Multi-protocol SerDes PHY

The 56 Gbps Multi-protocol SerDes PHYs is a comprehensive PAM-4 solution with available adjustable power through an integrated ADC that provides for future scalability in long-reach data center applications


Product Brief

R+ 1.25-16 Gbps Multi-protocol Serial Link PHY block diagram

56G PHY Subsystem Example

How 56G works

The Rambus 56 Gbps Multi-Protocol SerDes (MPS) PHYs are a PAM-4 and NRZ compliant IP solutions that provide reliable performance across challenging long-reach data center environments. A 28 GS/s ADC integrated directly into the architecture enables future scalability and extended reach. With high performance and multi-protocol compatibility, the PHYs support data rates from 9.95Gbps to 58Gbps across copper and backplane channels with more than 35dB channel insertion loss in a wide range of industry-standard interconnect protocols. Flexible system design is enabled through the ability to control the power consumption of the PHY.

The 56G MPS are designed with a system-oriented approach, taking the interface, interconnect and channel into account when optimizing performance and features to maximize flexibility in today’s most challenging system environments and applications. This makes the PHYs ideal for many long-reach, copper and backplane enterprise environments.

Available in an advanced FINFET Process

Solution Offerings

Protocol Compatibility

ProtocolData Rate (Gbps)Application
400GAUI-8 LR53.125Telecom and networking
400GAUI-8 MR53.125Telecom and networking
100G-KR4 LR25.78125Telecom and networking
10G-KR10.3125Telecom and networking
CEI56G-LR36 – 58Copper backplane networking
CEI56G-MR36 – 58Chip-to-Chip connectivity
CEI28G-MR19.9 – 28.1Copper backplane networking
CEI25G-LR19.9 – 25.8Copper backplane networking
CEI11G-LR9.95 – 11.2Copper backplane networking

SerDes Signal Integrity Challenges at 28Gbps and Beyond

Maintaining signal integrity has become increasingly difficult as data rates moves past 28Gbps to 56Gbps and beyond. Up to 28Gbps rates, NRZ is the preferred and standardized encoding scheme which consists of 1’s and 0’s. NRZ is also referred to as PAM2 (pulse amplitude modulation, 2-level), due to its two amplitude levels which contain 1 bit of information in every symbol. With serial data rates hitting 56 Gb/s per channel, signal impairments caused by increased bandwidth has prompted the high-speed serial data industry to adopt PAM4, or 4-level pulse amplitude modulation. For PAM4 signals, the baud rate equals one-half the bit rate and the Nyquist frequency equals one-fourth the bit rate. Compared to PAM2/NRZ, PAM4 cuts the bandwidth for a given data rate in half by transmitting two bits in each symbol. This allows engineers to double the bit rate in the channel without doubling the required bandwidth.

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