PCB Design Guidelines: Agilex™ 3 FPGAs and SoCs

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ID 853726
Date 8/20/2025
Public
Document Table of Contents
Document Table of Contents x
1. Overview 2. BGA Footprint and Land Pattern 3. General PCB Design Considerations 4. VPBGA PCB Routing Guidelines 5. MBGA PCB Routing Guidelines 6. EMIF PCB Routing Guidelines (VPBGA and MBGA) 7. MIPI Interface Layout Design Guidelines (VPBGA and MBGA) 8. True Differential I/O Interface PCB Routing Guidelines 9. Power Distribution Network Design Guidelines 10. Document Revision History for the PCB Design Guidelines: Agilex™ 3 FPGAs and SoCs
1. Overview x
1.1. Agilex™ 3 FPGAs and SoCs Packages
2. BGA Footprint and Land Pattern x
2.1. Metal-Defined Board Pad 2.2. Spoked Pad 2.3. Wide Trace Metal-Defined Pad 2.4. Solder Mask-Defined Pad 2.5. Recommended Land Patterns
3. General PCB Design Considerations x
3.1. Impedance Tolerances 3.2. Reference Planes 3.3. Layer Assignment 3.4. Via Drill Size 3.5. Fiber Weave 3.6. PCB Traces 3.7. PCB Vias 3.8. AC Coupling Capacitors 3.9. Other Considerations
3.6. PCB Traces x
3.6.1. Zig-Zag Routing 3.6.2. Image Rotation
4. VPBGA PCB Routing Guidelines x
4.1. Pin Distribution and Ball Pitches 4.2. Fan-Out and Routing Strategy 4.3. Power Pins
5. MBGA PCB Routing Guidelines x
5.1. Typical Design Rules For Type-IV HDI in a 0.5 mm MBGA 5.2. HSSI Breakout 5.3. EMIF Breakout 5.4. GTS Transceiver PCIe* 3.0 Interface Design Guidelines 5.5. GTS Transceiver Ethernet 10G NRZ Interface Design Guidelines 5.6. DisplayPort Connectors 5.7. HDMI Connectors
5.4. GTS Transceiver PCIe* 3.0 Interface Design Guidelines x
5.4.1. Channel Recommendations 5.4.2. General Guidelines for PCIe* 3.0 Interface 5.4.3. PCIe* Add-In Card Edge Finger
5.5. GTS Transceiver Ethernet 10G NRZ Interface Design Guidelines x
5.5.1. Channel Recommendations 5.5.2. General Guidelines for Ethernet Interface 5.5.3. Quad Small Form-factor Pluggable and Small Form-factor Pluggable Connector Routing
6. EMIF PCB Routing Guidelines (VPBGA and MBGA) x
6.1. General DDR Signal Routing Guideline on PCB 6.2. General Notes for EMIF Routing Guidelines Table 6.3. LPDDR4 Interface Design Guidelines 6.4. LPDDR4 Simulation Strategy
6.1. General DDR Signal Routing Guideline on PCB x
6.1.1. FPGA DDR Break Out Routing 6.1.2. DRAM Break Out in Layout Routing 6.1.3. Ground Plane and Return Path
6.3. LPDDR4 Interface Design Guidelines x
6.3.1. LPDDR4 Memory Down Topology (Up to 32-bits Interface) 6.3.2. Tables for Comprehensive Routing Guidelines for Each LPDDR4 Signal
8. True Differential I/O Interface PCB Routing Guidelines x
8.1. True Differential I/O Specifications
9. Power Distribution Network Design Guidelines x
9.1. Agilex™ 3 Power Distribution Network Design Guidelines Overview 9.2. Power Delivery Overview 9.3. Board Power Delivery Network Recommendations 9.4. Board LC Recommended Filters for Noise Reduction in Combined Power Delivery Rails 9.5. PCB PDN Design Guideline for Unused GTS Transceiver 9.6. PCB Voltage Regulator Recommendation for PCB Power Rails 9.7. Board PDN Simulations 9.8. Agilex™ 3 Device Family PDN Design Summary
9.2. Power Delivery Overview x
9.2.1. Power Architecture 9.2.2. Rail Merger Requirements 9.2.3. Power Rails Specification 9.2.4. Decoupling Capacitors Recommendation
9.2.1. Power Architecture x
9.2.1.1. Power Budget 9.2.1.2. Power Tree
9.2.3. Power Rails Specification x
9.2.3.1. Power Nets 9.2.3.2. Power Rails Tolerance 9.2.3.3. Power Nets and Transient Specifications
9.2.3.1. Power Nets x
9.2.3.1.1. Agilex™ 3 Package Power Nets and Subsystems Details
9.2.4. Decoupling Capacitors Recommendation x
9.2.4.1. Agilex™ 3 FPGA Packages Board-Level Decoupling Capacitors Summary 9.2.4.2. Agilex™ 3 GTS Transceiver Board-Level Decoupling Capacitors Summary
9.3. Board Power Delivery Network Recommendations x
9.3.1. Board Decoupling Capacitors Guide 9.3.2. FPGA Core Fabric VCC Voltage Regulator Selection 9.3.3. Remote Sense Connections 9.3.4. Load Line Requirements 9.3.5. VCC Core Board Current Slew Rate
9.4. Board LC Recommended Filters for Noise Reduction in Combined Power Delivery Rails x
9.4.1. GTS Transceiver Rail Board Connection and LC Filter Recommendation Under Noisy Voltage Regulator
9.5. PCB PDN Design Guideline for Unused GTS Transceiver x
9.5.1. PDN Design Guideline for Unused GTS Transceiver
1. Overview
2. BGA Footprint and Land Pattern
3. General PCB Design Considerations
4. VPBGA PCB Routing Guidelines
5. MBGA PCB Routing Guidelines
6. EMIF PCB Routing Guidelines (VPBGA and MBGA)
7. MIPI Interface Layout Design Guidelines (VPBGA and MBGA)
8. True Differential I/O Interface PCB Routing Guidelines
9. Power Distribution Network Design Guidelines
10. Document Revision History for the PCB Design Guidelines: Agilex™ 3 FPGAs and SoCs

3.8. AC Coupling Capacitors

The layout design of AC coupling capacitors can impact the performance of the high-speed channel.
  • Use a capacitor of size 0402 or 0201 for a smaller parasitics and smaller footprint.
  • Place the AC coupling capacitors at the end of the device or connector instead of the middle of the trace routing.
  • Keep the placement of the AC coupling capacitors on the two lines of a differential pair symmetrical. Make sure that the fan in and fan out routing structures of capacitors are symmetric and make sure trace lengths on both sides of the capacitors are matched.
  • Avoid routing signals underneath the capacitor cut-out area.
  • Optimize the cut-out size under the capacitor and capacitor pad by using a 3D electromagnetic simulation tool for your specific stackup.
    • The following figure shows the cut-sizes of capacitors used in the reference design. Altera recommends that you use a rectangular cut-out under the capacitors area and circular or oval anti-pads for transition vias.
    • Adjust the cut-out sizes based on the specific PCB stack-up to minimize return loss as much as possible. Generally, a larger cut-out size corresponds to higher impedance.
    • Add excitations at both ends of the traces.
    • For optimization, start with a 30 to 35 mil gap between two AC capacitors. Adjust this gap value if the return loss and TDR results are unsatisfactory.
    • Consider cutting more layers under the capacitors to increase impedance. Aim to achieve a return loss lower than –15 dB at the Nyquist frequency, although lower than –20 dB is preferable. Additionally, keep the impedance change within the cut-out and transition vias area as slight as possible, ideally within ±5 Ω.
Figure 11. Cut-Out Simulation Setup Example of AC Coupling Capacitors


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