Aligning with Physical Components on the PCB - 2023.2 English

UltraFast Design Methodology Guide for FPGAs and SoCs (UG949)

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2023.2 English

The orientation of the device on the PCB should first be established. Consider the location of fixed PCB components, as well as internal device resources. For example, aligning the GT interfaces on the device package to be as close to the components with which they interface on the PCB will lead to shorter PCB trace lengths and fewer PCB vias.

A sketch of the PCB including the critical interfaces can often help determine the best orientation for the device on the PCB, as well as placement of the PCB components. After completion, the rest of the device I/O interface can be planned.

High-speed interfaces such as memory can benefit from having very short and direct connections with the PCB components with which they interface. These PCB traces often have to be matched length and not use PCB vias, if possible. In these cases, the package pins closest to the edge of the device are preferred in order to keep the connections short and to avoid routing out of the large matrix of BGA pins.

The I/O Planning view layout in the AMD Vivado™ IDE is useful in this stage for visualizing I/O connectivity relative to the physical device dimensions, showing both top-side and bottom-side views.

Thermal Tip: For thermally-challenged designs, be aware of device placement in relation to other high-power components to minimize thermal coupling and maximize airflow. Avoid placement where the device is positioned in the exhaust of another high-power component or where board heating might negatively impact the operating temperature. AMD recommends thermal simulation to understand how the placement and environmental conditions can affect the junction temperature of the device.

The following figure shows the I/O Planning view layout.

Figure 1. I/O Planning View Layout