AC constraint transformation for top-down analog design

In mixed designs, analog blocks are often the most difficult parts to realize, due to the large number of high-level constraints and the importance of second order effects. In this paper a method is proposed to automatically transform AC constraints from higher to lower levels of hierarchy within a top-down design methodology. The transformation consists of finding a linear approximation for the analytic expression of the transfer function for flat and hierarchical designs. A state-of-the-art filter design example illustrates the capabilities of the method.