Immunity macro model for linear regulator considering internal terminal voltage

In order to estimate undesired behaviors in ICs due to RF conducted electromagnetic disturbances, immunity macro models are necessary for prediction of malfunction at front-loading of the design process. In this paper, a mechanism of malfunction of an LDO (low dropout) voltage regulator is investigated from the aspect of the internal terminal in a circuit. Measurement results show that the DC drift of the internal reference voltage is the dominant factor in malfunction of the LDO voltage regulator used in this study. In addition, an immunity macro model called ICIM-CI considering internal functional blocks is proposed. The model consists of PDN (passive distribution networks) for representing the transmission and reflection characteristics of RF disturbance and IB (immunity behavior) describing relation between malfunction of IC and the reference voltage (an internal terminal voltage of the LDO voltage regulator). The proposed model can predict variation of immunity behavior when a bypass capacitor is added near the injection terminal of RF disturbance. The simulation results using the proposed model is in good agreement with measurement results.