When to use the Coilcraft Impedance Model

When to use the Coilcraft Impedance Model

Coilcraft offers advanced frequency dependent lumped element models for a majority of our catalog of power and RF inductors. The lumped element values were determined by optimizing the simulation model to an average of measurements. This method results in a model that represents as closely as possible the typical frequency-dependent behavior of the component within the model frequency range.
 
To build these models in SPICE, Laplace elements are used to describe the frequency-dependent impedance and resistance elements. SPICE simulators generally simulate slowly if at all when Laplace elements are included in a time domain simulation. For situations that require time domain simulations, use of the near ideal models that are included with LTspice is typical. To help increase accuracy of these time domain simulations, Coilcraft has developed the impedance model.
 
The impedance model utilizes a similar structure, and elements similar to the frequency dependent model, but with fixed values. Figure 2 below shows a comparison of the frequency response of the three model types for the same inductor (MSS1278-103). As expected, the response of the impedance model is much closer to the high accuracy frequency model than the basic inductor model included with LTspice.
 
To take things a step further Coilcraft also now offers a growing collection of saturation models, currently only offered for soft saturating power inductors. These use the same fixed value elements as the impedance model but with the added effect of a current dependent inductance.