1.6.2. Using the Correct Number of Power/Ground Via Pairs
Unless you change manually, the PDN Tool sets the Number of Power/Ground Via Pairs for each power group to the default value defined on the Stackup tab. For this case it is 50 as shown by the figure below.
PCB PDN design is highly dependent on the Number of Power/Ground Via Pairs. This contributes to the spreading inductance (Ls) in the PDN design. If the actual Number of Power/Ground Via Pairs in the PCB is less than the number defined in the PDN Tool, the PDN Tool reports optimistic results. It is important to set the correct Number of Power/Ground Via Pairs to match your device and PCB.
Always provide a dedicated via connecting each power and ground pin on the FPGA to the plane. For more information on the importance of the number of power and ground pin pairs refer to Knowledge Database note.
An increase in the Number of Power/Ground Via Pairs between the plane and FPGA reduces spreading inductance (Ls) and increases the high-frequency current delivery efficiency from the plane to the FPGA. This results in increasing the maximum effective frequency of the PCB PDN.
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