A Hybrid Equalizer for Protection of 1st-Order Delta-Sigma Modulator Against Side-Channel Attack

This article introduces a countermeasure against Side-Channel Attacks (SCA) designed for 1st-order Delta-Sigma Modulators (DSM). Initially, the operation of 1st-Order DSM is explained at both the model and circuit levels. The analysis then focuses on the charging and discharging processes of internal capacitors, which lead to a signal-dependent charge transfer through the supply. The susceptibility of DSM to side-channel attacks is identified, and a neural network-based SCA method tailored for DSM is proposed. To safeguard the DSM from SCA, a hybrid equalizer circuit is developed, which mitigates the Current-Domain Signature (CDS) of the DSM’s supply current. This hybrid equalizer protects the DSM by absorbing the CDS using a switched capacitor equalizer, while ensuring continuous operation of DSM through a step-down charge pump and static current source. It is demonstrated that the hybrid equalizer circuit effectively defends against SCA by introducing substantial noise into the prediction output, without significantly compromising the DSM’s signal quality.