Virtuosity: Layout Reuse Flow in Modgen

15 Sep 2019 • 4 minute read

Welcome back to my blog series on Virtuoso^® Module Generator (Modgen). In my first post, I gave an insight into the basic features of the tool and spoke about how Modgen provides tremendous advantages for analog layout automation. With changing demands, we’ve been continuously improving the Modgen tool to match the requirements.

In my second post, I spoke about an important new feature—Support for Stacked Devices in Modgen. Here’s my third post in the series, in which I’ll talk about the Layout Reuse Flow in Modgen, an important feature introduced for advanced-node PDKs.

Nowadays, everyone is talking about ‘reuse’—reuse plastic, paper, batteries, and so on. When we talk about software reuse, what we really mean is to create reusable software assets. The layout reuse flow in Modgen lets you extract layout characteristics in template form from existing Modgens or other groups of devices, which are the reusable assets. You can then apply these templates on new designs to create Modgens that are similar to the source. Isn't that convenient?

Here are the key advantages of the layout reuse flow:

Boosts layout productivity
Makes it easy to create Modgens
Reduces time and effort
Creates similar structural copies, and so ensures consistency

The Flow

It’s important to understand the flow before we talk about the implementation. So here you go…

Here's a flow chart that depicts the overall flow:

We know that Modgens can be created from either the Virtuoso Schematic Editor or the Virtuoso Layout Editor.

In the Virtuoso Schematic Editor, you can extract the parameters from existing Modgens in the design.
In the Virtuoso Layout Editor, you can extract the parameters from either the existing Modgens or a group of selected devices in the layout.

These extracted parameters are stored in a Modgen template file. You can run this template file on one or more target layouts to generate Modgens that are similar to the source layout.

This can be better understood using an example. In the following animation, the source is a layout view that contains a differential pair with dummies. Parameters are extracted from the source to create a Modgen template file, which is then applied to another differential pair to create a new Modgen that is similar to the source.

That’s how, with just a click of a button (or maybe a few clicks), you can create similar structural copies of a Modgen. It's that easy!

Do you want to create Modgens that are more-or-less similar, with slight changes, for example, in their pattern or abutment style? That’s also possible! Open the Modgen template file and make the required changes before generating a new Modgen. Having said that, let’s look at a Modgen template file and what information it contains.

Modgen Template File

A Modgen template file is a collection of parameters that can be used to create a gridded layout for matching structures. The file is in text format, and so is easily readable and editable. Modgen template files are stored at a convenient location for you to look at and customize as per your requirements.

Here are a few important Modgen parameters that are included in a Modgen template file:

Pattern
Abutment
Dummies
Spacing
Routing
Guard Ring

Go ahead and try out this amazing new feature!

Related Resources

Blogs

Rapid Adoption Kits

User Guide

Virtuoso Module Generator User Guide

Trainings

Videos

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