Product Documentation
Voltus-Fi Custom Power Integrity Solution XL User Guide
Product Version IC23.1, August 2023

2

Getting Started with Voltus-Fi-XL

This section contains an overview of Voltus-Fi-XL, its key features, and how to start working with the tool.

Overview of Voltus-Fi-XL

Voltus-Fi-XL is used for transistor-level power-integrity analysis, which includes multi-mode simulation (MMSIM) electromigration and voltage drop (EMIR) analysis for transistor designs. The target designs include analog, analog/mixed-signal (AMS), and custom digital designs of large sizes that are created using Virtuoso.

This product is tightly integrated within Virtuoso. The results of the analyses are displayed on the Virtuoso layout. Voltus-Fi-XL also generates text reports of the analyses and lets you query the analyses results to view specific violations in the layout. This is used to identify and debug regions of high IR drop and EM violations in the design. After analyzing the EMIR results, you can create power-grid views (PGVs) of the design block, which can then be used in Voltus for mixed-signal analysis.

Voltus-Fi-XL uses the simulation database generated by simulators—Spectre Accelerated Parallel Simulator (APS) and Spectre eXtensive Partitioning Simulator (XPS)—as inputs to perform EMIR analysis.

Voltus-Fi will be obsolete in the next base IC release. The “next-generation” solution, Voltus-XFi, is available in this release of Virtuoso. It offers significant improvements to the overall EM-IR flow, including a unified use model, simplified simulation setup, and faster loading of results. The Voltus-XFi license is backward compatible and can be used to run Voltus-Fi if needed.

A brief description of the capabilities of the two simulators is provided below.

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Key Features of Voltus-Fi-XL

The following table lists the key features of Voltus-Fi-XL.

Feature Description

Extraction

Supports the generation of the Detailed Standard Parasitic Format (xDSPF) file using Quantus. This file provides all the parasitic information of the design for performing simulation using Spectre.

Simulation-based analysis

Uses APS/XPS—direct or iterated method for EMIR analysis.

Support for multiple simulation results files for EMIR analysis

Supports the following:

  • Multiple bin files that contain simulation results for different nets from the same testbench
  • Multiple bin files that contain simulation results from different testbenches for the same design

Static current analysis 

Evaluates IR drop and EM currents based on user-provided subcircuit instance current consumptions without running a transient or DC simulation.

Signal net and power-rail IR drop analysis

Supports the following:

  • Solid shape highlighting
  • Displaying and querying results
  • Analyzing power-gated designs
  • The following plot types: peak and average IR drop, transistor voltage, peak and average tap current, RMS tap current, powergate current, powergate voltage, peak, average, and RMS resistor current, and effective resistance plots

Signal net and power-rail EM analysis

Supports the following:

  • Solid shape highlighting
  • Displaying and querying results
  • All types of EM analysis: peak, average, rms, AC-peak, and absavg
  • Text-based ICT file for specifying EM rules
  • Advanced EM rules with qrcTechFile for 20nm and below technologies
  • The emDataFile.txt file for backward compatibility in 28nm and above technologies

Static and dynamic PGV generation

Creates PGVs of an analog design block that can be used in Voltus for mixed-signal analysis.

Advanced debug features

Structural analysis is a shape-based geometrical analysis that is used to quickly identify power-grid weaknesses in designs and mark them on the Virtuoso layout for you to view and debug. Structural analysis cuts down on the sign-off analysis time. The following checks are supported:

  • Missing Via analysis
  • Via coverage ratio
  • Skewed via ratio

Effective resistance is calculated between any two nodes (pins, tap nodes, or subnodes), either on the same net or on different layers of the same net. This feature uses the DSPF file, used for Spectre simulation, and the SPGS feature of Spectre.

Least-Resistive Path (LRP) analysis helps you identify weakly connected instances in the design during early stages of power planning. It displays the worst IR drop violations and plots the LRP on demand for any node.

What-If analysis feature lets you analyze the impact of potential layout changes, without implementing these changes in the layout, and re-extracting the xDSPF file. These changes are also called the ECO changes.

Self-Heating Effect (SHE) analysis flow visualization and the thermal-aware DC EM flow visualization. You can view the results of the these analyses by plotting them on the Virtuoso layout to show the worst deltaT violations. You can then debug your design to reduce the self-heating effect.

Viewing Results in vfiplot

The vfiplot utility is used to view the results of the IR drop and EM analysis that is performed in Voltus-Fi-XL.

The key benefits of viewing the results of IR drop and EM analysis in vfiplot are as follows:

  • No dependency on the Virtuoso layout
  • Increased speed of visualization

Installation Information

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Running Voltus-Fi-XL in Batch Mode

You can run Voltus-Fi-XL as a batch command, running it from Virtuoso in non-graph mode. Batch mode is used when the simulation database is already generated, and you want to print the IR/EM text reports without viewing the plots on the layout.

The batch mode flow of Voltus-Fi-XL supports both the configuration file or the conf file and the command file, cmd_file.

To run Voltus-Fi-XL in batch mode, do one of the following:

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Running Voltus-Fi-XL in GUI Mode

The flow to run Voltus-Fi-XL in GUI mode comprises the following steps:

  1. Starting the Virtuoso Studio Design Environment
  2. Opening the Schematic or Layout View
  3. Launching Voltus-Fi-XL

Starting the Virtuoso Studio Design Environment

To start the Virtuoso Studio design environment, do the following:

Opening the Schematic or Layout View

You need to open the schematic or layout view of your design in the Virtuoso Schematic Editor or Virtuoso Layout Suite, respectively. To do this, use either the File menu or the Tools menu of the CIW.

File Menu of CIW

  1. Choose File – Open.
    The Open File form is displayed.
  2. In the File group box, select a Library, select a cell name from the Cells list or directly type the cell name in the Cell field, and select a View (either schematic or layout).
    Alternatively, you can click Browse to open the Library Browser – Open File window and select your design.
  3. In the Application group box, select an item from the Open with drop-down list.
  4. Select one of the Open for options: edit or read.
  5. Click OK.

Tools Menu of CIW

  1. Choose Tools – Library Manager.
    The Library Manager form is displayed.
  2. To select a library and its corresponding cell and view, click the item names in the order: Library, Cell, and View. Select schematic or layout in the View section.
  3. Double-click the view to open the design in the Virtuoso Schematic Editor or Virtuoso Layout Suite.

Launching Voltus-Fi-XL

You can run Voltus-Fi-XL from the Virtuoso Studio Design Environment in two ways. You can run it either from the Virtuoso Layout Suite using the plug-in option, or from the Virtuoso Analog Design Environment (ADE L/ADE XL) after adding the DSPF file and performing postlayout simulation with EMIR analysis.

From Virtuoso Layout Suite

  1. Choose Launch – Plugins – Voltus-Fi-XL.
    The Voltus-Fi-XL console opens.

From ADE L/ADE XL

The steps for launching Voltus-Fi-XL using ADE L are detailed below. The same steps can be used to launch Voltus-Fi-XL using ADE XL.

  1. From Virtuoso Schematic Editor or Virtuoso Layout Suite, choose Launch – ADE L.
    The ADE L window opens.
  2. Set up and run simulation, and generate the simulation database.
  3. In the main menu of the ADE L window, choose Results – EM/IR Data – Layout Analysis.
  4. In the Select Layout View form, select the cell name from the Cell drop-down list and click OK.
    The following windows open:
    • Voltus-Fi-XL console
    • IR/EM Results form of Voltus-Fi-XL
      Voltus-Fi-XL Console

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Specifying Simulation Settings in ADE L/ADE XL

Before you run simulation, you need to specify the simulation settings in ADE L/ADE XL. The steps required in ADE L are detailed below. The same steps can be used in ADE XL.

To specify simulation settings in ADE L, do the following:

  1. In the main menu of the ADE L window, choose Setup – Simulation/Directory/Host and specify the Simulator as spectre.
  2. Choose Setup – High Performance Simulation and ensure that APS and its Post-Layout Settings group box options are selected.
  3. Choose Setup – Model Libraries and load the appropriate model files.
  4. Choose Setup – Simulation Files and in the Simulation Files Setup form, specify the Definition Files and Parasitic Files (DSPF).
    The Definition File contains the UTI commands. This file is required for generating power-grid views in Voltus-Fi-XL.

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Specifying EMIR Analysis Settings in ADE L/ADE XL

Before performing EMIR analysis in Voltus-Fi-XL, you need to specify the EMIR analysis settings in ADE L/ADE XL. The settings required for static and dynamic EMIR analysis are different. The steps required in ADE L are detailed below. The same steps can be used in ADE XL.

Setting up Static EMIR Analysis

Static EMIR analysis estimates the IR and EM current density without performing a circuit simulation based on the user-specified current estimates in the static current file. To set up static EMIR analysis, do the following:

  1. In the main menu of the ADE L window, choose Setup – EM/IR Analysis.
    The Voltus-Fi XL Analysis Setup form opens.
  2. In the Analysis tab, select the Type of analysis as Static.
  3. In the Net Selection group box, click Select to choose the Net Name for the nets to be analyzed in the schematic. In the schematic, select an instance. Selecting an instance chooses all the nets of the instance with the wild card “*”.
  4. Specify the Static Current File.
  5. Select avg current analysis for both IR Drop Analysis and EM Current Analysis.
    By default, IR drop is calculated only for the power nets and not for the signal nets. For EM analysis, both the power and signal nets are considered.
  6. Click Add/Modify to add the net and analysis combination statements to the summary information in the EMIR configuration file.
  7. In the Solver tab, ensure that the Speed is set to default.
  8. In the Option tab, select an option from the Advanced Option drop-down list or specify the required option in the Additional Option field.
    The DSPF file included through the Simulation Files submenu of ADE L is automatically populated in the DSPF File Checking group box.
  9. Click Run to invoke the spfchecker.
  10. Select the EMIR Analysis for Static check box at the bottom of the form.
  11. Click OK to save the static EMIR analysis settings for the run.

Setting up Dynamic EMIR Analysis

Dynamic EMIR analysis requires a DC or transient simulation. To set up dynamic EMIR analysis, do the following:

  1. In the main menu of the ADE L window, choose Setup – EM/IR Analysis.
    The Voltus-Fi XL Analysis Setup form opens.
  2. In the Analysis tab, select the Type of analysis as Dynamic.
  3. In the Net Selection group box, click Select to choose the Net Name for the nets to be analyzed in the schematic. In the schematic, select an instance. Selecting an instance chooses all the nets of the instance with the wild card “*”.
  4. Select the analysis types from available options: IR Drop Analysis, EM Current Analysis, and Advanced IR Drop Analysis.
    Select the EM Current Analysis options, max and avg, if you want to perform AC-Peak analysis later in Voltus-Fi-XL.
  5. Click Add/Modify to add the net and analysis combination statements to the summary information in the EMIR configuration file.
  6. In the EM Rule Check Setup group box, specify the EM Tech File.
  7. In the Solver tab, select direct as the Solver Method.
  8. In the Time Window Setup group box, select an option to specify EMIR analysis duration.
    Full Transient is selected by default, which means the EMIR analysis is run over the entire simulation period. You can also select Time Window and provide the start and stop times.
  9. In the Option tab, select an option from the Advanced Option drop-down list or specify the required option in the Additional Option field.
    The DSPF file included through the Simulation Files submenu of ADE L is automatically populated in the DSPF File Checking group box.
  10. Click Run to invoke the spfchecker.
  11. Select the Enable EMIR Analysis in Transient or DC Simulation check box at the bottom of the form.
  12. Click OK to save the dynamic EMIR analysis settings for the run.

The Summary Information group box at the bottom of the Voltus-Fi XL Analysis Setup form is updated as you make changes in the form or click Add/Modify where applicable. The summary section contains the final set of commands in the EMIR configuration file. This file is later used by Spectre APS for performing EMIR analysis.

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Generating Simulation Database in ADE L/ADE XL

After specifying simulation and EMIR analysis settings, you need to run a simulation in ADE L/ADE XL to generate the simulation database.

To do this:

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Accessing Documentation and Help

You can access the Voltus-Fi-XL documentation and Cadence Help using one of the following methods:

From the Command Prompt

  1. Change to the following directory: installation_dir/tools/bin
  2. Enter the following command:
    ./cdnshelp
    After launching Cadence Help, press F1 or choose Help – Contents to display the help page for Cadence Help.

From the Voltus-Fi-XL GUI

Do one of the following:

From Cadence Online Support

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Voltus-Fi-XL Console Description

The following main menus of Voltus-Fi-XL are available. In addition to the menus, there is a Stop Process button in the console. This button is enabled when you run a process. Click this button to stop a process while it is running.

Menu Description

Extraction

Opens the Extract xDSPF form that lets you generate an xDSPF file.

Simulation

Opens the Setup and Run Current Analysis form that lets you set up and run the static current analysis mode for peak current analysis.

IR/EM Analysis

Opens the following forms:

  • IR/EM Results: Lets you view the IR drop and EM analysis results.
  • Create Power Grid Views: Lets you create PGVs.
  • Connect and vfi: Lets you connect to the port and opens the vfi form using which you can view the IR drop and EM analysis results.

Hierarchical EMIR

Opens the following forms for performing hierarchical EMIR analysis:

  • Create Power Grid Views: Lets you create block-level PGVs and xDSPF files.
  • Extract xDSPF: Lets you generate the top-level xDSPF file.
  • Hierarchical Top Simulation: Lets you perform top-level simulation.

Help
  • Opens the Voltus-Fi Custom Power Integrity Solution XL User Guide and the Voltus-Fi Custom Power Integrity Solution XL What’s New chapter in the Virtuoso What’s New document.
  • Provides the version information of Voltus-Fi-XL.

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