Comparing apples and oranges: Evaluating model-coverage using acceptance regions

Analog/Mixed-Signal (AMS) design and verification is dominated by modelling tasks. Model validity is crucial for the design's correctness but lacks a more formal criterion. We propose a novel model verification strategy to evaluate the coverage with respect to a given circuit. We define model-coverage based on the individual acceptance regions in parameter space. This imposes a measure that can be formally described and efficiently approximated by an industrial simulation environment. We prove the ability of our approach in a case study: A model of a clock-recovery component used in RFID tags is compared to the realized circuit and layout. Using the novel coverage measure, we match the model to the circuit: By systematically adding new constraints to the model code, the coverage is increased to 99% ensuring the correctness of the overall system verification.