Identification and break of positive feedback loops in Trojan States Vulnerable Circuits
Zhiqiang Liu, You Li, Yan Duan, R.L. Geiger, Degang J. Chen · 2014
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.