External Memory Interfaces Agilex™ 7 M-Series FPGA IP User Guide

ID 772538
Date 11/18/2024
Public
Document Table of Contents

6.4.5.1. Single Rank and Dual Rank x 8 Discrete (Component) Topology

This section discuss the single rank x8 and dual rank x8 memory down topology design guideline.

The following design example demonstrates a single rank x 8 memory down topology. You can adjust the design topology based on the actual PCB design (single rank x 8 or dual rank x 8)

The interface covers data bytes (DQ/DQS), address signals, command signals (BA, BG, RAS, CAS, WE, ACT, PAR), control signals (CKE, CS, ODT) and clocks (CLK).

Figure 26. Signal connections for DDR4 Single Rank × 8 Discrete Topology
Table 129.  Specific Routing Guidelines for Single Rank x8 Discrete Memory Topology for All Supported Signals in the Interface
Signal Group Segment Routing Layer Max Length (mil) Target Zse (ohm) Trace Width, W (mil) Trace Spacing, S1 (mil): Within Group Trace Spacing, S2 (mil): CMD/CTRL/CLK to DQ/DQS Trace Spacing, S3 (mil): DQ Nibble to Nibble Trace Spacing (mil), Within DIFF pair Trace Spacing (mil), DQS pair to DQ Trace Spacing (mil), CLK pair to CMD/CTRL/CKE Rtt / Ctt
Segment Total MB
CLK BO1 US 50 To first DRAM: 4000 To last DRAM: 9600   4 5, 17 17   4   17 R1=36Ω C1=10nF
BO2 SL 1000   4 5, 17 17   4   17
M SL   40 5.5   3h   4   3h
BI1 US 50   3   3h   4   3h
BI2 SL 700 50 3   3h   4   3h
T1 SL 300   3   3h   4   3h
T2 US 50   3   3h   4   3h
CMD, CTRL, Alert BO1 US 50 To first DRAM: 4000 To last DRAM: 9600   4 5, 17 17         R1=36Ω

alert_n requires an external pullup resistor to VDD (1.2V) of approximately 1KΩ.
BO2 SL 1000   4 5, 17 17        
M SL   40 5.5 2h 3h        
BI1 US 50   3 2h 3h        
BI2 SL 700 50 3 2h 3h        
T1 SL 300   3 2h 3h        
T2 US 50   3 2h 3h        
DQ BO1 US 50 5000   4 5, 17   17        
BO2 SL 1000   4 5, 17   17      
M SL   45 4.5 2h   3h      
BI US 50   4 2h   3h      
DQS BO1 US 50 5000   4       4 17    
BO2 SL 1000   4       4 17  
M SL   45 4.5       4 3h  
BI US 50   4       4 3h  
For an explanation of the guidelines represented in this table, refer to the bullet points immediately following Figure 22.