Analysis of Shunt LDO With Physical Security to Power/EM Side-Channel Attacks

With growing concerns over physical security against power and electromagnetic side-channel attacks (SCA), this work provides a comprehensive analysis of different existing isolation countermeasures, especially the analysis of security-focused shunt low-dropout regulators (LDOs). Using both small-signal and large-signal analysis, we demonstrate that shunt LDOs offer superior security using the metric current-domain signature attenuation (CDSA) and load supply isolation (LSI) performance while mitigating mid-frequency power-supply ripple-rejection (PSR) peaking. Various existing shunt LDO architectures are evaluated, highlighting trade-offs between DC rejection and high-frequency CDSA response. Alternative isolation techniques such as galvanic isolation, digital LDOs, and integrated voltage regulators (IVRs) are also examined.