A New Analytical Approach for Developing an Equivalent Circuit Simulation Model for a Chip Inductor, Based on Manufacturer Specifications Given in the Datasheet

Inductors represent a very complex behavior especially in the field of RF techniques. Some manufacturers offer SPICE models for their inductors built up by lumped elements. The lumped element values are determined by matching the simulation model to an average of the measurements. This leads to curious numbers, and if the model is used in a simulation tool, all these values have to be adjusted if the inductor is changed. Often there are no models and measurement files available, so just the data sheet specifications are given that can be used for the work. Especially in the RF techniques several physical effects have to be taken into account and it is not sufficient to just assemble the inductor in a real circuit whose value derives from a simulation tool that works with ideal elements. The presented method shows the development of a lumped element equivalent circuit model for an inductor that is just dependent on these given datasheet specifications. The equations are tested and verified with the suggested SPICE model and the datasheet parameters of different manufacturers. The results show that the new model fits very well over the whole frequency range up to the self-resonant frequency of the element. Slightly differences of the simulated quality factors can be neglected because for the measurements the element has to be soldered on a defined printed circuit board yielding to additional losses caused by the soldering process and several coupling effects. It was shown that a simple equivalent circuit with three lumped elements results in a very good compliance of a real inductor specified by only very few parameters in the datasheet. The equations to calculate the values for the lumped elements can now be used independently from the simulation tool or mathematic software program.