PCB Design Guidelines (HSSI, EMIF, MIPI, True Differential, PDN) User Guide: Agilex™ 5 FPGAs and SoCs

ID 821801
Date 8/29/2025
Public
Document Table of Contents

6.5.4. Skew Matching Guidelines for DDR4 Memory Down Configurations

The following table shows skew matching guidelines for DDR4 down-memory topology. These skew matching guidelines apply to both single rank and dual-rank memory down topologies.

Table 15.  Skew Matching Guidelines for DDR4 Memory Down Topology
Length Matching Rules Time
Length matching between DQS and CLK -85 ps < CLK - DQS < 935 ps
Length matching between DQ and DQS within byte -3.5 ps < DQ - DQS < 3.5 ps
Length matching between DQS and DQS# < 1 ps
Length matching between CLK and CLK# < 1 ps
Length matching between CMD/ADDR/CTRL and Clock -20 ps < CLK - CMD/ADDR/CTRL < 20 ps
Length matching among CMD/ADDR/CTRL within each channel <20 ps
Include package length in length matching Required