Switching Induced Substrate Noise and Mixed-Signal Receiver Design

We use a stochastic model of the switching current to describe the power spectral density of current noise waveforms induced by digital switching events. We discuss common impedance paths, particularly arising from non-ideal properties of electronic packages, that couple this noise into the substrate of an integrated circuit. We derive estimates of the noise spectrum for modest digital power and typical package characteristics and evaluate the noise in the context of RF mixed-signal designs. The results show severe noise coupling via this particular mechanism. Implementation of analog front-end circuits in a predominantly digital chip requires differential LNA circuits capable of eliminating large common-mode signals arising from the substrate coupling.