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Virtuosity: An Introduction to Modgen

Rapid advancements in the semiconductor industry have resulted in an ever-increasing need for analog layout automation. Analog circuits often use structures such as current mirrors and differential pairs, where grouping and matching of device characteristics are vital. Virtuoso has paved its way through these challenges by providing high-end tools that ensure faster convergence on design goals and efficient layout implementation.

In this blog, I'll give you an overview of one such tool—the Virtuoso® Module Generator, popularly known as Modgen. 

Understanding Modgen 

Modgen allows you to create highly matched arrays of devices directly on the canvas. The tool provides options to select the required instances and group them into a gridded layout, which you can then customize as per your requirements. 

One of the most useful features of Modgen is that it can be used from both Virtuoso Schematic Editor and Virtuoso Layout Editor.

Here's an animation that highlights the key features of Modgen:

Modgen GUI Options

Virtuoso provides a very intuitive and powerful interface to create and customize Modgen. You can edit Modgen in two modes:

  • Using the Modgen Editor 
  • Using the Modgen On-Canvas Commands

Do you want a dedicated space to view and edit your Modgen? The Modgen Editor window is the solution to all your customization needs, with options that are neatly organized in toolbars and assistants.

  • Modgen Toolbars: In the Modgen Editor window, you'll find these toolbars:
    • Modgen Placement Toolbar, which helps you customize the Modgen member devices and their configurations to suit your requirements. For example, you can add dummies, insert body contacts and guard rings, specify device alignment and spacing, abut or unabut devices, and merge layers. That's not it - there are many more options for you to explore!
    • Modgen Routing Toolbar, which lets you visualize, configure, and store routing topologies. For example, you can create trunks, add straps and twigs, set the channel width, and route using the pin to trunk router.
  • Modgen Pattern Assistants: Includes the Grid Pattern Editor (GPE) and Grid Pattern Mapping (GPM) assistants, which are available as dockable assistants in the Virtuoso Layout Suite. GPE lets you view and manipulate grid patterns and place devices, whereas GPM lets you view and edit the schematic-to-layout symbol mapping of the Modgen members. These assistants are synchronized with the layout on canvas.

Are you in the middle of a task and want to edit a Modgen without opening the Modgen editor window? You can use the Modgen on-canvas editing options to create and customize Modgen directly in the layout canvas.

Explore these features and let us know what you liked most about them!

Modgen in Scripts

Do you know that you can perform the same set of tasks using SKILL APIs?

In fact, Modgen constraints are stored as Modgen sandbox objects, which are actually Modgen Pattern Editor User-Type Description Objects. Modgen provides several APIs to edit these Modgen sandbox objects by running scripts—just as how you would do it using the UI options.

To know more about these APIs, see the Modgen Placement and Routing Functions section in the Virtuoso Layout Suite SKILL Reference manual.

Going Forward ...

The Modgen tool has been continuously evolving to provide better analog layout automation capabilities. There are two new features added to Modgen—Support for Stacked Devices and Support for Reusable Modgen Templates.

In my subsequent blogs, I'll focus on these two new features. Stay tuned!

Related Resources

Blogs

Rapid Adoption Kits

User Guide 

For more information on Cadence circuit design products and services, visit www.cadence.com.

About Virtuosity

Virtuosity has been our most viewed and admired blog series for a long time that has brought to fore some lesser-known, yet very useful software and documentation improvements, and also shed light on some exciting new offerings in Virtuoso. We are now expanding the scope of this series by broadcasting the voice of different bloggers and experts, who would continue to preserve the legacy of Virtuosity, and try to give new dimensions to it by covering topics across the length and breadth of Virtuoso, and a lot more… Click Subscribe to visit the Subscription box at the top of the page in which you can submit your email address to receive notifications about our latest Virtuosity posts.

Happy Reading!

Aneesh Shastry

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