Effectiveness of embedded capacitors in reducing the number of surface mount capacitors for decoupling applications

摘要

Purpose - The purpose of this paper is to present an analytical approach to find the reduction in the required number of surface mount capacitors by the use of embedded capacitors in decoupling applications.rnDesign/methodology/approach - The analytical model used to perform decoupling is cavity model from theory of microstrip antenna and N-port impedance matrix. The methodology involves addition of decoupling capacitors between the power and the ground plane such that the impedance between ports on the power-ground plane becomes lower than the target impedance at that frequency. A case study is presented in which a 0.3 m × 0.3 m power-ground plane is decoupled by using various combinations of surface mount capacitors and embedded capacitors in the frequency range of 0.001-1 GHz and at a target impedance of 0.1, 0.01, and 0.001 fi. The total number of surface mount capacitors are compared in each case. Findings - Use of embedded planar capacitors with a thin dielectric (about 8 mm) dampened board resonances at high frequency, as compared to a thick dielectric. Embedded capacitors are found to reduce the number of surface mount capacitors when the target impedance is low and the operating frequency is high.rnResearch limitations/implications - The methodology discusses in this paper is applicable to a simplified power-ground plane (which has no cutouts and is rectangular in shape) as compared to actual digital circuits.rnOriginality/value - This methodology can be used as a quick preliminary tool to evaluate the decrease in the number of surface mount capacitors (by the use of embedded capacitors) as compared to complex and time consuming electromagnetic solvers.