On More Dependable Assertion-Based Verification

The increased design complexity of analog/mixed signal (AMS) systems puts a high pressure on researchers to find the efficient solutions for the verification of these systems. In contrast to digital designs, the nonlinear nature and higher sensitivity of AMS systems to parameter variations make the verification process more difficult. The focus of this paper is the verification of system robustness with respect to frequency and phase properties. For this purpose, the method, which combines simulation with assertion-based approach, is used. Assertions describing desired system properties use simulation results to verify the system behaviour. In order to provide more formal results using simulation-based methods, deviations of system parameters are modeled as ranges and superimposed to the nominal design model. The range-based representation of parameter values delivers formal model of AMS system for the considered parameter set. Hence, its simulation results in the range-based system response containing the set of simulation traces reachable for all parameter values lying in the specified ranges. The applicability and efficiency of the proposed simulation-based formal method is shown through the verification of PLL phase properties with respect to frequency.