On the Susceptibility of Embedded Thermal Shutdown Circuit to Radio Frequency Interference

This paper deals with the susceptibility to RF interference of a temperature sensor used in smart power system-on-chip to shut down the source of heat or the overall device in the case of overtemperature. Such a sensor is usually buried within the power section; hence, it is parasitically coupled with the power transistors and for this reason its operation can be affected by the disturbances superimposed onto the power transistors´ nominal signals. In this work, the detrimental effect of the RF interference on a common thermal shutdown circuit is analyzed using an approximate nonlinear model and performing time-domain computer simulations. The results of these analyses show that RF interference can induce false fault signaling. To avoid this, a simple and effective layout solution that improves the immunity of such kind of circuits is proposed and its effectiveness is proved by experimental test results.