Investigations on the susceptibility of smart power ICs to RFI

This paper deals with the susceptibility to radio frequency interference (RFI) of the analog front-end circuits embedded in smart power integrated circuits (ICs). The parasitic coupling of the power section with the analog and the digital section of these devices through the silicon substrate is discussed referring to a macro model, then the causes of RFI demodulation in analog front-end circuits are highlighted. In particular, it is shown that the RFI injected in the silicon substrate through the power devices is demodulated by the input stage of the analog front-end embedded in the same silicon die. On the basis of these analysis, a simple method to increase the immunity to RFI is presented and its effectiveness is proved through a set of measurements carried out on a test chip.