PCB Design Guidelines: Agilex™ 3 FPGAs and SoCs

ID 853726
Date 8/20/2025
Public
Document Table of Contents

6.2. General Notes for EMIF Routing Guidelines Table

These general notes apply to the EMIF routing guidelines tables in subsequent topics.
  • All spacing requirements are the minimum requirement to be met on PCB in EMIF routing guidelines table.
  • In the routing guideline table, 'h' represents the trace-to-nearest-reference-plane height or distance. Use the formula in the routing guide table to calculate the correct spacing requirements.
  • There is no differential impedance target for CLK and DQS signals. Follow the EMIF routing table and keep traces closely-coupled.
  • The trace length and spacing in the guideline table are based on FR-4 level PCB material and PCB layout routing with the worst-case crosstalk. You can perform simulation if you do not follow the requirements in the routing guide table.
  • 'SL' stands for stripline routing recommendation and 'US' stands for upper surface (microstrip) routing recommendation in guideline tables.
  • You must design trace widths of BO, BO1, BO2, and BI based on the actual PCB stack-up and PCB design. Preferably, design the trace widths of BO, BO1, BO2, and BI closer to target impedance of the M segment.
  • Include the FPGA package per pin skew and PCB delay for skew matching.
  • Length matching is not required on the Alert and Reset signals.
  • Altera recommends that you perform skew matching in picoseconds.
  • The minimum trace widths specified in the BO and BI sections of the guideline table are 3 mil for MBGA (stripline and microstrip) and VPBGA (stripline), and 4 mil for VPBGA (microstrip). Altera recommends using wider spacing in the PCB layout when feasible.