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Interface IP

PCIe 4.0 SerDes PHY

The Rambus PCI Express (PCIe) 4.0 SerDes PHY is designed to maximize interface speed in the difficult system environments found in high-performance computing. It is a low-power, area-optimized, silicon-proven IP designed with a system-oriented approach to maximize flexibility and ease integration for our customers. With the Northwest Logic Expresso 4.0 controller core it comprises a complete PCIe 4.0 SerDes subsystem. Alternatively, it can be integrated with PIPE 4.2-compliant 3rd-party controllers. The PCIe 4 SerDes PHY supports PCIe 4.0, 3.0, and 2.0 and has full support for manufacturability.

How the PCIe 4.0 Interface Works

The Rambus PCIe 4.0 PHY with the Expresso 4.0 digital controller comprise a high-performance serial link subsystem. Optimized for power in challenging, high-loss channels, our PCIe 4.0 interface solution is ideal for performance-intensive data center, edge and graphics applications.

The PHY comes complete with a PMA hard macro that supports PCIe 4.0, 3.0, and 2.0 protocols and a physical coding sublayer (PCS) soft macro for PCIe that is PIPE 4.2 compliant. Co-verified with the Northwest Logic Expresso 4.0 digital controller, the PHY can also be integrated with 3rd-party PIPE 4.2-compliant controllers.

PCIe 4.0 Interface Subsystem Example
PCIe 4.0 Interface Subsystem Example

The PHY has a minimal set of broadside control and are configurable in x2, x4 and x8 lane configurations. This gives the PHY improved flexibility and support for a wide range of applications. The PCIe 4.0 PHYs is rigorously tested through 3rd-party compliance testing and internal interoperability system testing.

In order to improve system margin and performance, our solution features transmit and receive equalization and full equalization adaptation. This ensures that data is recovered even in the presence of channel and system interference.

Our PCIe 4 SerDes PHY is available on TSMC, Global Foundry and Samsung process nodes.

Solution Offerings

  • Duplex lane configurations of x2, x4, and x8
  • Flexible ASIC clocking
  • Tight skew control of 2UI between lanes of the PMA
  • 3-tap Tx Finite Impulse Response (FIR) equalizer with multi-level de-emphasis
  • Deterministic latency within +-1UI variation for Tx lane
  • Continuous time linear equalizer (CTLE) with programmable settings providing up to 12dB gain peaking at Nyquist frequencies
  • Automatic calibration of key circuits to maximize performance and yields
  • Support for bifurcation and quadfurcation modes
  • 6-tap Rx DFE (decision feedback equalizer)
  • Second-order CDR meeting SSC and RX sinusoidal jitter requirements
  • Expandable register interface enabling communication with multiple PMAs and PCS-BIST soft macros
  • Built-in Self Test (BIST) with ATPG and AC/DC boundary scan support
  • Built-in PRBS pattern generation and checking for standalone loopback testing
  • In-situ real-time monitoring and receive data eye schmoo
  • Operation across a wide temperature range (-40 C to +125 C)
  • Includes ESD structures
  • SRIS support
  • PMA Hard Macro
    • Verilog models
    • LEF abstracts (.lef)
    • Timing models (.lib)
    • CDL netlists (.cdl)
    • ATPG models
    • IBIS-AMI models
    • GDSII layout
    • DRC & LVS reports
  • PCS-BIST Soft Macro
    • RTL model
  • Datasheet
  • SoC Integration guide
  • Optional design integration and bring-up support services
SerDes Signal Integrity Challenges at 28Gbps and Beyond

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. 

Protocol Compatibility

ProtocolData Rate (Gbps) Application
PCIe 2.04High bandwidth peripherals and graphics cards
PCIe 3.08Enterprise solutions and chip to chip connectivity
PCIe 4.016Hyperscale data center and big data applications


Phase Interpolator-Based CDR

Reduces cost, power and area of clock and data recovery (CDR) circuit and improves jitter performance in high-speed parallel and serial links versus PLL-based CDRs.