Identification and break of positive feedback loops in Trojan States Vulnerable Circuits

A systematic method is proposed for automatically identifying and breaking positive feedback loops (PFLs) in Trojan States Vulnerable Circuit. The method first converts the netlist of a circuit into a directed dependency graph (DDG) and then partitions the DDG into strongly connected components (SCCs). It then employs graph theory techniques to detect all PFLs and locate the break-points for every SCC. The proposed method could identify the circuit´s vulnerability to Trojan States only by its structure without the computation of DC solutions and it also provides insights on how and where to break the PFLs such that break-loop continuation methods can be applied. With Sub-Bandgap reference and widlar-Banba examples, it is demonstrated that the proposed approach can effectively identify all the PFLs and break-points.