Faster projection based methods for circuit level verification

As VLSI fabrication technology progresses to 65 nm feature sizes and smaller, transistors no longer operate as ideal switches. This motivates the verification of digital circuits using continuous models. Recently, we showed how such verification can be performed using projection based methods.However, the verification was slow, requiring nearly four CPU days to verify a nine-transistor toggle flip-flop. Here, we describe improvements to the reachability algorithms and optimizations of the software architecture. These produce a 15 x reduction in computation time and significant reductions in the overapproximation errors. With these changes, the same toggle flip-flop can be verified in a few hours, making formal verification a viable alternative to circuit simulation.