A low-cost closed-form transient thermal mode for area-efficient power MOS sizing and reliable inductive load switching

Using an on-chip low-side power MOS with the clamping function to control currents through inductive loads offers low system cost in automotive applications. The chip area and the reliability of the integrated power MOS depend on its junction temperature. This paper presents a closed-form transient thermal model that can be evaluated by a simple numerical method to provide the junction temperature estimations based on its power profile as well as power MOS´ areas and aspect ratios during the inductive clamping. This aids circuit designers in designing an area-efficient integrated power MOS to meet a given reliability requirement while being lower cost than commercially available thermal simulation tools. The proposed theoretical transient thermal model of the integrated power MOS is verified to achieve reasonable accuracy compared with the experimental results.