Modeling the thermal transients in automotive power ICs

This paper discusses the modeling of the thermal transient at the proximity of a dominant heat source in a 5 V Low Drop Out (LDO) regulator used in an automotive environment. The LDO regulator is designed using a 60 V BCD technology having a 2 μm-linewidth and dual layer metal interconnect. A SPICE circuit model using spherical spreading of heat through silicon is developed to predict the transient thermal behavior of the LDO regulator. Simulations indicate a 65 mV drop in the output regulated voltage for a power pulse of 1.4 W through the output power transistor and are in excellent agreement with that obtained from experiments. The design of the thermal generator and the effect of the thermal resistance and capacitance on the output regulated voltage are also discussed