A new VLSI decoupling circuit for suppressing radiated emissions from multilayer printed circuit boards

This paper presents a new decoupling circuit for multi-power-terminal VLSIs to suppress strong radiated emissions caused by power plane resonance of multilayer printed circuit boards (PCBs). This circuit is based on a previous π-network filter consisting of two capacitors and one power trace. The power trace, designed in agreement with transmission line theory, was used in place of the ferrite bead inductor of a conventional π-network filter. The new circuit has been so designed that when a number of them are applied in combination to a multi-power-terminal VLSI, they can share capacitors, thus reducing the total number of capacitors required. Both calculated and measured high-frequency characteristics of power buses in PCBs show that in wide-band frequencies this new circuit isolates a VLSI, the source of switching noise, from power distribution buses, which would otherwise resonate that switching noise. Measurements of emissions from PCBs mounted with a 208-pin VLSI demonstrate that this circuit reduces emission levels more effectively than does conventional capacitor-only decoupling circuit