Power Distribution Network Design Tool
The easy-to-use power distribution network (PDN) design tool is a graphical tool used with Stratix® II GX FPGAs to optimize the board-level PDN. The purpose of the board-level PDN is to distribute power and return currents from the voltage regulating module (VRM) to the FPGA power supplies, and support optimal transceiver signal integrity and FPGA performance. Figure 1 shows the different components of the PDN.
Figure 1. Model of the Power Distribution Network
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For each power supply, PDN designers have to choose a network of bulk and ceramic decoupling capacitors. While SPICE simulation could be used to simulate the circuit, the PDN design tool provides a fast, accurate and interactive way to determine the right number of decoupling capacitors for optimal cost and performance trade-offs. By determining the optimal set of decoupling capacitors for a given design, board space can be saved and board layout is made easier.
You select the number and values of the capacitors in the spreadsheet (see Figure 2) and the tool calculates the composite impedance of the PDN along with the impedance characteristics of the VRM, the decoupling capacitors and their mounting inductance, the printed circuit board, and the FPGA with on-package and on-chip capacitors.
Figure 2.Spreadsheet Entry for PDN Optimization
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Optimal performance is achieved if the composite impedance meets the target impedance (see Figure 3). The target impedance is derived from FPGA power requirements. Altera's Quartus® II development software PowerPlay power analysis technology allows you to accurately analyze the FPGA's power consumption for each power rail.
Figure 3. Impedance Results after PDN Optimization
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The PDN design and optimization process is described in detail in the Power Distribution Network technical brief of Altera's High-Speed Board Design Advisor. The advisor provides tested and proven guidelines and the best design practices for key aspects of your high-speed board design,
Design with confidence using Altera’s tools and board design guidelines and get your design right the first time with the right performance and cost trade-offs.
Contact your Altera® sales representative for a copy of the PDN tool.
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