1 Introduction

As automotive systems are refined to reduce cost and size, power densities invariably increase. Holding semiconductor efficiency constant, more power equates to higher junction temperatures. Junction temperatures above the specified limits can reduce system reliability and shorten module life span. To avoid such problems and costly system redesigns, early thermal analysis is critical.

Accurately predicting junction temperatures is not an easy task. Many factors become data inputs that influence thermodynamic behavior. The problem becomes more challenging because some of the key data inputs, such as PCB layout, are only accurately known after the design is complete! Without a reliable way of predicting thermal properties, system designers can become locked in an inefficient cycle; a cycle where failed designs lead to redesigns in an iterative an unnecessarily protracted process.

To prevent lengthy design times, expensive development costs, and system unreliability it is imperative that system designers understand how to quickly get a feel for, and determine the thermal properties of a system.

This application report identifies and demystifies system components and other less tangible quantities that fuel input to the thermal analysis engine. The components of the engine are presented and their function is explained. The engine’s output propels efficient system design, as temperature data becomes available.