A Study of Current Density Limits Due to Saturation in Thin Film Magnetic Inductors for On-Chip Power Conversion

Saturation in thin film coupled magnetic inductors was measured as a function of dc current in both windings. A simple mathematical model was created to approximate the inductor saturation level in the presence of the two currents. The model was compared both to FEM calculations of saturation in a linear model and to the experimental findings. Using the mathematical model, an expression for the maximum dc current and maximum flux levels in the yokes was derived for a two phase coupled buck converter, as a function of coupling.