Analytical Modeling of Power Pin Impedance in Parallel Power & Ground Planes

An analytical model is developed for the driving point impedance of a power pin for the evaluation of a decoupling capacitor's effectiveness. The model accounts for the finite sized parallel-plate ground-power pairs and is validated against a numerical electromagnetic method. The proposed method is also used in the assessment of pin impedance in a comparative study involving multiple representative locations of a power pin on a rectangular plane. In addition to the pin-capacitor distance, the angular dependency of impedance is demonstrated in the evaluation of the capacitor's effectiveness and a physics based explanation is provided using the developed expression. From the interpretation of the results, a generic design rule is proposed for the placement of decoupling capacitors on parallel-plates.