FastSpice Simulators: Advantages, Challenges, and the Way Forward

 

Introduction:

FastSpice simulators are powerful simulation tools for the pre- and post-layout verification of complex semiconductor designs such as DRAM, flash, SRAM, and transistor-level SoCs. They offer a significant increase in simulation speed, typically around 2X faster compared to traditional SPICE simulators. However, this speed comes at the cost of accuracy and reliability, with deviations of approximately 5-10% when compared to SPICE simulators. FastSpice simulators achieve their speed enhancements through various techniques, including specialized solvers, pre-processing of linear systems, partitioning, RC reduction/optimization, multi-rate time step control, look-up table models, and array optimization.




Popular FastSpice Simulators:

Some of the popular FastSpice simulators in the market today include Synopsis' FineSim-Pro and PrimeSim XA, as well as Cadence's Spectre X and Spectre FX. These simulators can also be utilized for mixed-mode circuit simulations by combining both analog and digital simulation approaches. For example, combinations such as FineSim-Pro with VCS, VCS with XA, and Spectre FX with Xcelium are commonly employed.

Challenges and Limitations:

While FastSpice simulators offer significant advantages in terms of speed and capacity, they come with their own set of challenges. These simulators are not plug-and-play solutions and require additional effort and expertise to set up and run effectively. They demand more powerful computing resources and can be more challenging to debug compared to traditional SPICE simulators. Furthermore, FastSpice simulators do not currently support all the models and features available in traditional SPICE simulators, particularly for low nodes/FinFETs. However, ongoing efforts are being made by vendors such as Synopsis and Cadence to address these limitations.

The Way Forward:

To overcome the challenges associated with using FastSpice simulators, vendors should leverage their extensive knowledge and expertise in handling different standard circuits, such as PLLs and ADCs, as well as technology models. This can be achieved by utilizing techniques from Artificial Intelligence and Machine Learning (AIML) to build a comprehensive database. Such a database would provide optimized verification environments for standard SoCs, offering significant benefits to verification engineers during the accuracy/preset option setup and ramp-up stages. By automating these processes, engineers can reduce manual effort, streamline verification tasks, and enhance overall productivity.



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