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This paper presents a methodology for the creation of reduced thermal models of electronic systems based on the knowledge of the system dynamic temperature response. The registration of thermal responses using equidistant sampling on a logarithmic time scale allows the proper identification of all the time constants in the responses. Knowing the entire time constant spectrum, it is possible to generate a reduced dynamic thermal model in the form of an RC Cauer ladder with a limited number of stages. This simple model assures not only short simulation time and provides excellent accuracy but also allows the identification of certain physical parameters of a system. The methodology is illustrated in the paper based on the example of discrete power devices attached to a heat sink and cooled with forced air flow. The reduced thermal model is suitable for the direct implementation in the SPICE simulator or almost any other multiphysics simulation environment.