NanGate Library Validation platform is a comprehensive and easy to use tool suite for standard cell library verification which is fully integrated with Nangate’s library creation and characterization flow.
Nangate Library Creator™ verifies format-specific errors, performs extensive layout validation and does comprehensive cross-view checks. This last feature – detailed on Figure 2 – ensures consistency at each step of library creation by performing cross-checks to inspect each view in the library (GDSII, LEF, Spice, Liberty and Verilog/VITAL) and by ensuring all common contents match.
Nangate Library Characterizer™ verifies the electrical behavior of each cell by simulating and validating against their functional description extracted from Spice netlist and input Liberty. It first checks that Liberty and Spice netlist match and then automatically generate the required stimuli to run fast simulations and then perform the required analysis to ensure electrical correctness. The tool can also be used as second source characterization (restricted to re-characterization mode) to double check values generated by the reference flow are correct and accurate. Nangate Library Characterizer™ in re-characterization can automatically extracts most of the setup used to generate the original timing, power and noise figures from the original Liberty file.
Nangate Liberty Analyzer™ performs sanity and coherence checks on Liberty files to validate that the library is ready to use with any design flow. It handles multiple NLDM, NLPM, CCS and ECSM models at library, cell, pin and individual arc levels while providing insightful statistical data. It displays and plots differences for easy spotting of trends and outliers and to assess performance of different libraries from different vendors. It also has unique QoR capabilities that provide quick insight about the quality of a cell family and across similar group of cells (e.g. compare current drive-ability across cells of same nominal drive strength). This is the same tool that’s used at the end of library re-characterization to compare the performance of two different characterization runs.
NanGate Design Audit™ ensures characterization accuracy and robustness in library constraints (such as setup and hold). The tool has proven over the past few years to greatly improve productivity in timing closure and library development process. It enables design teams to check timing accuracy through Spice versus STA analysis, automatically extracting the n-most critical paths on reference gate-level designs and comparing Spice simulation of these critical paths against their STA results. It supports industry golden standard STA tools such as Synopsys PrimeTime™. It also supports the use of test circuit structures to allow detailed library qualification as early as in the library development phase. Spice vs. STA validation can be used along with the library characterization process, establishing a closed-loop methodology for fine tuning characterization settings in order to obtain more accurate values. The Spice vs. STA flow is shown below.
The unique Constraint Validation feature of NanGate Design Audit™ – also integrated inside NanGate Library Characterizer™ – completes the list of timing accuracy validation features in the Nangate Library Validation platform. This feature allows timing constraints in sequential cells, such as setup and hold time, to be validated through Spice simulation. It flags optimistic and pessimistic timing constraints and provides valuable data to assess design margins and quality of the library characterization process, displayed in clear and meaningful reports. It also alerts the user for constraint values that do not guarantee safe operation independent of guard-band used. Constraint Validation is an automated way to verify if a Liberty file respects user-defined settings and to discover such settings when they are not known beforehand (reverse engineer), going beyond a simple Liberty-Liberty comparison.