Influence of Skin Effect on MOSFET Losses

As the personal computer makers push for DC-DC converters delivering 200 Amps at 1 V within the next three years, the semiconductor manufacturers are pushing to optimize their MOSFET by improving both the silicon and the packages to provide switching devices suitable for these challenges. In this paper we address the parasitic resistance attributed to the package alone and in isolation from the silicon on-resistance. We show that in most of the traditional packages this resistance has a very strong frequency dependant component. This means that at a switching frequency of about a few megahertz, this parasitic resistance will constitute a large percentage of the total device on-resistance. Based on this observation, we concentrate on the synchronous buck converter and we derive conduction loss equations that are frequency dependent and calculate actual losses and examine several effects that follow