A new framework for high-level synthesis of analog and mixed-signal integrated systems is introduced. It focuses on the translation of a functional description into a behavioral model of a specific architecture with values for the parameters of its building blocks. An initial, simple, high-level solution is evolved into a more realistic low-level result by applying appropriate transformations of both architecture and parameters. This top-down heterogeneous optimization algorithm deals readily with multifarious performance characteristics and diverse types of objectives, and integrates various sources of design knowledge and types of transformations. Furthermore, it creates the architecture rather than selecting it. As illustration of the methodology, a tool, ANTIGONE, has been written that allows to generate different types of A/D converters depending on the specifications like speed and accuracy.