Shreeve dv club_ams


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Shreeve dv club_ams

  1. 1. Verilog-AMS for Mixed-Signal Integrated Circuits Powering Your Ideas.TM Zilker Labs September 30, 2006
  2. 2. Introduction Integrated Circuits are increasing in Size and complexity. More complex interface between digital and analog makes verification difficult. 2
  3. 3. Previous Simulation Solutions Mixed signal simulation with two simulators – Complex interface elements – Convergence issues – Slow simulation Verilog simulation – Analog must be modeled as discrete with limited checking – No analog results Spice simulation – Need synthesized netlists – Very slow simulation 3
  4. 4. Verilog-AMS Verilog-AMS is a mixed signal language and simulation tool that can be used for mixed signal modeling and simulations. Benefits of using Verilog-AMS – Simplification of modeling mixed signal circuits – Possible to greatly decrease simulation time – Mixed signal verification – Architecture design and validation 4
  5. 5. Modeling Improvements Verilog-AMS uses most constructs from Verilog and Verilog-A languages – Analog and digital content can be contained in one model Signals can be declared as “logic” or “electrical” – This allows for a model to have both digital and analog I/O – If done correctly, no connect modules or interface elements will be needed 5
  6. 6. Modeling Necessities Polarity of I/O and dependency on control signals Dependency on analog signals (power, biases, etc). Timing Bandwidth, Slew rate, and Voltage limits of analog signals 6
  7. 7. Special Model Considerations Some models may be created with a fast/ accurate option Hierarchy of circuits should match physical placement – All pin names and directions the same as the schematics – Same circuit name to be easily imported Matching of signal types!! – Important for simulation time 7
  8. 8. Zilker Labs Design Flow 8
  9. 9. Successes CVS use of netlists and models No problems with analog/digital interfaces due to polarity mismatch or timing issues Less chance for miscommunication in the conveying the operation of the circuits Fast simulation at the top level – More circuit functionality verified before tape-out – Standard testbenches with pass/ fail outputs for regression testing System level simulation Functional samples at 1st Silicon 9
  10. 10. Areas of Improvement Incorporate models into schematic environment – Allows for common testbenches – Better verification of model accuracy Architecture level modeling using Verilog-AMS 10
  11. 11. Conclusion Verilog-AMS can greatly improve design cycles by – Increasing verification of digital to analog interface at the top level of the design – Significantly reducing the top level simulation time. – Determining appropriate analog specifications for analog circuits. – Creating an appropriate environment for chip architecture design. 11