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One of Alessandra Nardi’s favorite quotes is, “You can’t direct the wind, but you can adjust the sails.” An R&D group director on Cadence’s electrical signoff team, Nardi is inspired by the philosophy behind this German proverb. Nardi, who has a PhD in electrical engineering from UC Berkeley, has certainly adjusted the sails of her engineering career, embracing a diversity of EE disciplines along the way. We sat down recently to discuss her work so far in helping to overcome the obstacles of electrical signoff. Listen in.
Tell me about your educational and professional background.
I’ve always liked math, science, and physics, and subjects that are very quantitative. You always have an explanation and they have to be supported by facts. Like with bugs—you can build a test case to prove or disprove something. I debated between physics and electrical engineering, but engineering is more diverse.
I joined Cadence in 2013 after working at Magma. I have a background in power integrity, timing analysis, and library characterization.
What are your key responsibilities at Cadence?
I drive strategic projects that can help improve our current solutions or create differentiation for our products. These improvements can also cross boundaries of specific products. For example, I’m currently working on improvements to the Effective Current Source Model (ECSM) power model together with the Virtuoso Liberate team in our custom products group.
When it comes to power integrity, what are customers struggling with the most?
Accuracy is the most important thing because you are the last gate before taping out. What makes it really challenging is the size. If you look at the power grid, the number of nodes is easily two billion. Additionally, SPICE-like waveforms are used to model the current supplies accurately. With these kinds of numbers, runtime and memory can become prohibitive. So capacity and runtime need to be superlative to enable this type of analysis. Otherwise, if the power integrity tool is not efficient, it can be a bottleneck.
Customers tell us they don’t care about power integrity as long as it doesn’t impact timing. But a lot of the engineers who specialize in timing are not power integrity experts. There might be one person on a team who is an expert, so ease of use of the tool is important. So, too, is automation, in terms of automatic fixing capabilities.
How is Cadence addressing these customer challenges via the Voltus IC Power Integrity Solution?
The Voltus solution has a specialized SPICE solver that guarantees the accuracy of the solution. At the same time, it supports distributed processing and multi-threading that guarantees excellent runtimes with no loss of accuracy. The Voltus solution also supports the diverse set of functionalities that are part of power integrity, such as electromigration analysis, electrostatic discharge analysis, and power-up analysis. The feature set is very rich and addresses customer needs to ensure their power grid is properly designed via power profiling, vector-less and vcd-based power analysis, effective resistance analysis, etc.
As chips continue to grow larger and more complex, what are some new timing signoff challenges that design engineers will need to address?
Engineers used to assign a budget for voltage variations, and as long as your grid could support that, things would be fine. Guaranteeing that margin is getting more and more complex as routing resources are limited. So the request we hear more and more often is to actually now interleave power integrity analysis with timing analysis, to relieve some of the pressure on voltage variation budget and only fix the power grid when it affects timing closure.
More and more, there are mixed-signal designs. Now, you cannot ask a digital designer to learn both tools, and you cannot ask an analog designer to learn both tools. How do we make the interface more seamless in our tools? We are doing more integration in our tools to address this.
Package and board design also affects power integrity analysis. These are typically handled by two separate groups—the chip-centric team gets a package model and the package-centric team gets a die-model. Connection and integration of these tools needs to be painless and seamless.
What does an EDA vendor need to do to stay on top of emerging signoff challenges?
It is a given that we need to keep innovating the technology for even better capacity and performance, but it is also key that we offer a holistic solution that goes beyond the individual signoff analysis by itself and covers the challenges that are going across boundaries of different domains. Some examples are what I mentioned before: joint power and timing analysis, more automated power-integrity fixing capabilities, seamless integration between digital and mixed-signal solutions, easy connection between the chip-centric and the package-centric domains.
With this in mind, I found it quite useful over the years to have expertise in different areas: it is easier to connect the dots, understand the overall requirements, and drive to create complete solutions and flows.
There’s been much discussion about the dearth of women in technical fields. What advice would you give to a woman who’s interested in pursuing a career in engineering?
They key is to do it if they like it. They need to have fun, enjoy going through the day. If there are challenges, whether you’re a woman, an immigrant, or whatever, try to improve the situation by looking at things you can control. Diversity can be fruitful if there’s a respectful relationship. Be yourself, listen to others, share what you think.
What, in your opinion, makes an engineering career rewarding?
With the combination of expertise and the tool, you can actually beat the competition—that is rewarding. It’s also a combination of technology and people skills. What I like about engineering is that you can have some of both: you can have technical discussions and you can also win with relationships, with building a team, making them happy. I can gain trust by showing we are competent, we know what we are doing. You build relationships of trust with colleagues, customers, and your competitors.