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.