Abstraction models and use models in mixed-signal verification Hi folks! I am back! If you recall, in my previous post (Part 1), I outlined the key drivers behind the increasing need for mixed-signal verification today. In this post, I want to elaborate on the challenges and tradeoffs inherent in the different design abstraction models and verification use models that are prevalent today. First, what are design abstraction models and how do they differ? The answer lies in the level of design abstraction (cell-level, macro-level, block-level, full-chip or SoC-level), the type of design (analog, mixed-signal), how you choose to verify your design and what your verification objectives are. Abstraction models and verification use models usually go hand-in-hand. Traditionally, custom designs at the cell-level, macro-level, and block-level, are verified using what is known as the “Analog Top” or “SPICE Top” model. This model entails a bottom-up SPICE-centric verification approach wherein, the design is verified in SPICE netlist format using a SPICE testbench and a SPICE simulator (e.g., HSPICE). While this model ensures high verification accuracy, it is not scalable i.e., it cannot be extended to very large designs or full-chip verification, due to the performance/capacity limitations of SPICE simulators. But there are exceptions – discrete analog designs typically are verified using this model even at the full-chip level, but by using a FastSPICE simulator (e.g., CustomSim), and by incorporating limited behavioral modeling using System Verilog, Verilog, or Verilog-A, to alleviate the capacity constraints of the simulator. The figure below depicts such a scenario:
The increasing need for mixed-signal verification!