Behavioral Modeling of Mixed-Signal Circuits

Abstract

With the widespread usage of SoC’s containing mixed-signal circuits, verifying the behavior of top level mixed-signal ICs is becoming more costly and complicated. ICs contain both analog and digital content with several levels of interaction between both domains, these mixed-signal ICs need to be simulated with both the analog and the digital content, to do so, co-simulation or mixed-signal simulation is carried out, this special type of simulation requires an analog simulator to handle simulating the analog transistor-level circuits, and a digital event-based simulator to handle the digital HDL content, the mixed-signal simulator handles the synchronization and adapting the signals between the digital discrete time, logic-state based domain and the analog continuous time, continuous amplitude domain. These simulations need to be carried out under a multitude of test scenarios to ensure the correct operation of the chip in different modes and under different inputs. These simulations can be very time consuming due to the presence of the analog solver that needs to solve huge circuit matrices, several techniques exist to model analog behavior using a higher abstraction (analog HDL languages).