Chapter 5
Analog/Mixed-Signal Verification
Analog/mixed-signal (AMS) verification proves the correct implementation of analog and digital design portions and specifically addresses interactions between the two domains.
A number of techniques can be combined to fulfill different design and verification requirements:
- AMS system designers follow a top-down methodology in which Simulink reference models provide a framework for component-level design.
- Analog designers can import Simulink models into circuit-level simulators to help design and verify analog design components.
- Mixed-signal IC designers can import circuit-level simulation data in MATLAB for analysis, visualization, and reporting.
- Design teams can perform interactive debugging of AMS designs using Simulink with circuit-level simulators through cosimulation.
- Digital hardware designers can analyze how their designs interact with analog portions of designs by importing C code generated from Simulink.
Export Components from Simulink Models to AMS Circuit-Level Simulators
Mixed-signal models in Simulink can be imported into AMS simulators such as Cadence Virtuoso® AMS Designer through use of the SystemVerilog DPI-C interface.
From Simulink, you can generate C code along with a SystemVerilog wrapper that allows integration with the AMS simulator. Once compiled, the generated model runs natively within the circuit simulator. While this approach does not provide the visibility that’s possible with cosimulation, it will simulate faster since there’s no need to synchronize two different simulators.
Exporting models from Simulink into the circuit simulator can save engineers time that would be spent developing circuit-level testbenches and real-number behavioral models.
Exporting Simulink behavioral models for AMS circuit-level simulation.
The Mixed-Signal Analyzer app enables IC designers to import databases of circuit simulation results directly from Cadence ADE Explorer and Virtuoso ADE Assembler. Once the data is imported, designers can visualize waveforms, identify trends, and generate reports.
Users can choose from more than 40 built-in MATLAB functions to analyze results. Additional flexibility can be achieved by using proprietary MATLAB functions.
Trend chart in Mixed-Signal Analyzer app.
Users can automatically import databases without having to manipulate large and numerous files enabling them to compare results, isolate corners, and gain insights into the circuit implementation in shorter time. Once the analysis is completed, designers can generate reports to share across the organization.
In AMS cosimulation, the design is partitioned between Simulink and a circuit-level simulator such as Cadence Virtuoso AMS Designer. Simulink behavioral models can be simulated together with the circuit implementation of AMS designs. Coupler blocks provide the interface between Simulink and Cadence Virtuoso AMS Designer.
During cosimulation, engineers can use the debug facilities of both Simulink and circuit-level simulators. This visibility is helpful to design, debug, and verify a mixed-signal system.
Cosimulation speed can be slow due to the synchronization between the two variable-step simulators and the complexity of the circuit-level implementation.
Mixed-signal cosimulation of Simulink with Cadence Virtuoso AMS Designer.
For hardware designers developing the digital components of mixed-signal designs in RTL, it’s often helpful to be able to simulate the analog portions that interact with digital components as they are being designed and verified.
You can generate C code from portions of high-level Simulink models of portions of the design under test (DUT). The C code is generated with a SystemVerilog wrapper that allows it to be compiled and integrated with the HDL simulator via its DPI. Prior to code generation, Simulink models representing analog behavior should be discretized based on accuracy and simulation performance requirements, enabling their use in digital simulators.
A Mixed-Signal Model-Based Design Flow for Automotive Sensors
A senior director of engineering from Allegro MicroSystems describes their evolution of a model-based mixed-signal ASIC design flow for the development of high-integrity automotive sensor ICs. Allegro’s usage spans streamlined UVM-based verification, rapid prototyping, and automatic RTL code generation for mixed-signal sensor ICs.
