Agilex™ 7 Device Family High-Speed Serial Interface Signal Integrity Design Guidelines

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ID 683864
Date 11/20/2024
Public
Document Table of Contents
Document Table of Contents x
1. Signal Integrity (SI) in High-Speed PCB Designs
1. Signal Integrity (SI) in High-Speed PCB Designs x
1.1. Supported Protocols 1.2. Channel Insertion Loss (IL) Budget Calculation 1.3. PCB Materials and Stackup Design Guidelines 1.4. PCB Design Guidelines 1.5. Document Revision History for the Agilex™ 7 Device Family High-Speed Serial Interface Signal Integrity Design Guidelines
1.3. PCB Materials and Stackup Design Guidelines x
1.3.1. Mitigating Insertion Loss with Dielectric Material 1.3.2. Power Layers 1.3.3. Reference Planes 1.3.4. Layer Assignment 1.3.5. Impedance 1.3.6. Via Drill Size 1.3.7. Fiber Weave 1.3.8. Reference Stackup
1.4. PCB Design Guidelines x
1.4.1. General PCB Design Guidelines 1.4.2. E-Tile PCB Design Guidelines 1.4.3. F-Tile PCB Design Guidelines 1.4.4. P-Tile PCB Design Guidelines 1.4.5. R-Tile PCB Guidelines
1.4.1. General PCB Design Guidelines x
1.4.1.1. PCB Traces 1.4.1.2. PCB Vias 1.4.1.3. Connector Breakout 1.4.1.4. AC Coupling Capacitor 1.4.1.5. Others
1.4.3. F-Tile PCB Design Guidelines x
1.4.3.1. F-Tile Features and Capabilities 1.4.3.2. Optimizing the Passive Channel 1.4.3.3. COM Simulations 1.4.3.4. Simulating the Active Channel
1.4.5. R-Tile PCB Guidelines x
1.4.5.1. R-Tiles Features and Capabilities 1.4.5.2. R-Tile Design Layout Examples 1.4.5.3. Landing Pad Cut-out Optimization of AC Coupling Capacitor 1.4.5.4. R-tile HSSI Breakout Routing in BGA Area and MCIO connector Pin Area 1.4.5.5. AC Coupling Capacitor Placement Around MCIO Connector 1.4.5.6. PCIe Gen5 Add-in Card Edge Finger Breakout Design Guidelines
1. Signal Integrity (SI) in High-Speed PCB Designs

1.3.1. Mitigating Insertion Loss with Dielectric Material

PCB routing from FPGA device to high-speed connectors has very strict IL requirements, for example, high speed Ethernet to the optical module interface and PCI Express* (PCIe) to the gold finger interface.
  • Use the following dielectric constant (Dk) and dissipation factor (Df) values as a reference only for low-loss and ultra-low-loss dielectric materials. Test your design with a vector network analyzer (VNA).
    • Dk =3.5 and Df =0.007 (at 1 GHz) for low-loss material
    • Dk =3.4 and Df =0.002 (at 1 GHz) for ultra-low-loss material
  • Use low-surface-roughness copper materials such as RTF2, VLP, HVLP, and HVLP2 copper to mitigate insertion loss caused by the skin effect. Copper resistance is a function of frequency, as when the frequency increases, the resistive loss increases because of the skin effect. This skin effect reduces the cross-sectional area of the transmission line, which increases the copper resistance.
  • A thicker dielectric between the signal and ground planes reduces the dielectric loss while wider traces increase the effective surface area and reduce the sheet resistance.
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