Virtuosity: Debugging like a Pro Using Voltus-XFi Result Browser: Strategies to Boost Efficiency

Welcome to the second part of our blog series on Cadence Voltus-XFi Customer Power Integrity Solution. In the previous installment, we embarked on a fascinating journey exploring how Voltus-XFi can boost productivity by running your EMIR signoff analysis 3 times faster. But the pure runtime of the EM-IR analysis is only one part of the equation. As designs become more complex and intricate, the other crucial aspect -“efficient debugging” - demands our attention. When you deal with networks of 10s of millions of parasitic resistors, it is critical to maintain an overview and tweak your design at the right spot to fix violations. Today’s blog is the first out of three, focusing on how easy it can be to review and resolve potential power integrity issues when using the Voltus-XFi Result Browser.

Before diving into the details, let’s quickly review the different result types that are displayed at the end of an EM-IR analysis with Voltus-XFi: we can distinguish between the node-based and resistor-based results.

One example of a node-based result is the IR drop that represents the potential at a certain node in a circuit. Other examples of node-based results are the effective resistance at a node or tap currents. Resistor-based results on the other hand, represent a quantity through a parasitic resistor in the network. These could be currents, as well as the ratio of the current to the design rule limit (EM).

As you can imagine, these results quickly stack high up as it involves a huge amount of data, and finding the relevant information is akin to searching for a needle in a haystack. Luckily this requirement has been an important priority right from the inception of Voltus-XFi development. All results are efficiently stored in a structured database, enabling speedy querying of results while providing a foundation for powerful debugging features as well. These features can be accessed from the main debugging cockpit. which is the Voltus-XFi Results Browser. The browser is implemented as an assistant in the Virtuoso Layout Editor and is tightly integrated with the layout canvas with which you are already familiar. No new tool, no new layer palette, and no new hotkeys to learn!

Getting an Overview of the Situation

Sometimes (and especially when you work on the top-level layouts), loading the layout view and all its dependencies might take some time, and you just want to get a quick overview of how “healthy” your circuit is. In Voltus-XFi, you can access this information without any delay right from the Results section after running the EM-IR analysis:

In a single view, you can spot the nets violating the EM limit (highlighted in red) as well as how bad those violations are. Using the same table, you can also find the max IR drop and further details about the nets’ parasitics. If your design does not show any EM violations and the max IR drop is within your specifications, well, congratulations, you are already done here!

Occasionally, you might see from this Net Summary that the results don’t make much sense, and something was completely off in the analysis. In such a case, you might take a step back into the Setup section and review the settings like EM temperature, EM techfile, and so on rather than digging deep into the detailed results. If the overall results look reasonable, but you still see some nets having violations, the next step would be to load the detailed results onto the layout view.

Getting Into the Details

This is where the Voltus-XFi Results Browser Assistant comes into play.

The top section of this assistant will show the net summary with the violating nets highlighted in red. Double-clicking on this net will load the detailed results in the lower half of the assistant. In the IR tab, you will be able to see all the node-based results, and in the EM tab, you can find all the resistor-based results. Now, you can use several features in Voltus-XFi to locate and fix the weak spot:

The cool thing with Voltus-XFi is that it is integrated as an assistant in the Virtuoso Layout Editor. This helps tremendously to visualize the violations in the context of the actual layout. But not only is reviewing made easy you can also make the cell view editable and use all the functionality of the layout editor to change the layout and fix the violation right from the same window! Following a clear debugging strategy is key to quickly identifying the root cause and fixing it.

In today’s blog post, we introduced you to the Voltus-XFi debugging capabilities and how they can help you:

• Gain an overview into the complexity of 10s of millions of resistors using the summary table
• Work efficiently on the actual layout view with Voltus-XFi Results Browser assistant in Layout Editor

In the next blog, we will be exploring the strategies in Voltus-XFi to resolve high IR drops. Stay tuned for our next post.

Related Resources

Rapid Adoption Kits	Voltus-XFi Rapid Adoption Kit
User Guides​	Voltus-XFi User Guide
Blogs	Driving Super-efficient Chip Design with Voltus-XFi Custom Power Integrity Solution Accelerate Your EM-IR Closure with Voltus-XFi Custom Power Integrity Solution Introducing Spectre X EMIR Voltus-XFi

For more information on Cadence Voltus-XFi Custom Power Integrity Solution, visit www.cadence.com/voltus-xfi.

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