External Memory Interfaces (EMIF) IP User Guide: Agilex™ 5 FPGAs and SoCs

ID 817467
Date 7/08/2024
Public

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8.3.1. LPDDR4 PCB Stackup and Design Considerations

The following figures show an example of a PCB stackup with 14 layers that has been used on PCB design for an Altera platform board. You may use other stackups (thin such as PCIE board or thick board) if you meet the recommendations in this guideline.

The figure below shows a 14L thin board, high performance Type-IV PCB with micro vias, stacked vias, buried vias and through vias.

Figure 35. 14L Thin Board, High Performance Type-IV PCB Stackup

The figure below shows a 20L thick Type-III Board stack-up (high performance with PTH with/without backdrill example used at Altera platform boards and development kits.

Figure 36. 20L Thick Type III Board Stackup

A type-IV PCB is a precise and high-quality PCB. This type-IV PCB utilizes not only PTH vias to connect from top to bottom layers, but also stacked vias, micro vias and buried vias to connect between layers. For example, a full-height stacked via of a 14-layer PCB is made up of a combination of dual-stacked micro vias and buried vias.

The following figure depicts a cross-sectional comparison of a PTH and a stacked via.

Figure 37. Cross-sectional Comparison Between PTH and Stacked Via