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

ID 821801
Date 12/06/2024
Public
Document Table of Contents

5.4.3. Power Delivery Recommendation for DDR4 Discrete Configurations

This section describes PDN design guidelines for the memory side in memory down topology.

The total number of decoupling capacitors is based on single channel; if multiple channels are sharing the same power rail, the number of decoupling capacitors at memories for all channels should be scaled accordingly. You can use smaller decoupling capacitors in memory PDN design to minimize area, inductance, and resistance on the PDN path.

The following table shows the required quantity and capacitance of decoupling capacitors on the memory side.

Table 16.  PDN Design Guidelines for the Memory Side in Discrete Topology
Memory Configuration Power Domain Decoupling Location Quantity × Value (size)
Device-down 1Rx8 VDDQ/VDD shorted 4 near each x8 DRAM device 36 × 1 uF (0402)
Distribute around DRAM devices 9 × 10 uF (0603)
VPP 2 near each x8 DRAM device 18 × 1 uF (0402)
Distribute around DRAM devices 5 × 10 uF (0603)
VTT Place near Rtt (termination resistors) 16 × 1 uF (0402)
Place near Rtt (termination resistors) 4 × 10 uF (0603)
Device-down 1Rx16 VDDQ/VDD shorted 4 near each x16 DRAM device 18 × 1 uF (0402)
Distribute around DRAM devices 5 × 10 uF (0603)
VPP 2 near each x16 DRAM device 10 × 1 uF (0402)
Distribute around DRAM devices 3 × 10 uF (0603)
VTT Place near Rtt (termination resistors) 8 × 1 uF (0402)
Place near Rtt (termination resistors) 2 × 10 uF (0603)