An Effective Global Approach for Assessment of Decoupling Capacitors on Mixed Planar and Transmission Line PDNs

A global analysis technique is proposed to calculate the effectiveness of decoupling capacitors on practical power delivery networks (PDN). The proposed method is based on separation of a PDN into its power transmission lines (PTL) and non-PTL sections. The PTL section consists of circuit components with the highest impact on the impedance of the specified power pin, including the pin itself, the nearest capacitor and segments of PTL on both sides of the capacitor. The rest of the PDN makes up the non-PTL section which could be composed of planar shapes, PTLs or a mixture of both. The non-PTL section is characterized as a distributed circuit, preferably using an electromagnetic (EM) simulator. The effectiveness of the capacitor is measured by the self-impedance of the pin which depends on the distance between them. The pin impedance is cast in a transcendental equation in the PTL section including the impedance of the non-PTL section. The optimal placement of the capacitor is calculated using an iterative approach. With the proposed method, the use of an EM simulation at each step of the iteration is eliminated, significantly speeding up the computation process. The proposed method is validated on real-life design cases.