A capacitor selector tool for on-board PDN designs in multigigabit applications

This paper presents a capacitor selector software tool for a proper on-board Power Distribution Network (PDN) design in those high-speed applications which have strict requirements on voltage noise up to the first hundreds of megahertz. Current commercial tools for PDN design only offer a manual choice of the capacitor value and their number simulating the board impedance profile. This manual resolution becomes very hard when the design has high power consumption and noise requirements are very strict. The aim of this software is to solve a basic on-board PDN design minimizing the number of "change simulate-analyze" iterations that have to be carried out in the manual PDN design. This software, PDN Designer, uses the FDTIM method introducing some design specifications. Thus, it offers an on board PDN design with low number of capacitors, reducing space on board and total cost. A particular case of PDN design using PDN Designer will be shown for a module using multigigabit optical connectors connected to an Altera Stratix II GX FPGA. This board is working with data rates of 75 Gbps for a high-energy physics application. Results of PDN Designer for this board are introduced in Cadence Allegro SPB 16.2 PI tool, obtaining an impedance profile that meets noise specifications and validates the PDN design.