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Cadence recently published the Mixed-Signal Methodology Guide, a first-of-its-kind book that offers a comprehensive review of the design, verification and implementation techniques required for today's complex mixed-signal designs. The book has 11 lead authors, including three from outside Cadence. Recently I talked to several of the authors about their roles in the book and the messages they are conveying through it.
The Mixed-Signal Methodology Guide shows that traditional, ad-hoc approaches to analog/mixed-signal design and verification are no longer sufficient for today's mixed-signal systems-on-chip (SoCs) and semiconductor IP. It offers detailed descriptions of new methodologies and techniques that are needed, including analog behavioral modeling, metric-driven verification, electrically-aware design, IC/package co-design, and highly collaborative mixed-signal physical implementation.
I reviewed a preliminary version of the book in May, but several new chapters are included in the published version. Here's an updated chapter listing. You can read the preface and see brief chapter summaries by clicking here.
1. Mixed-Signal Design Trends and Challenges2. Overview of Mixed-Signal Design Methodologies3. AMS Behavioral Modeling4. Mixed-Signal Verification Methodology5. A Practical Methodology for Verifying RF Designs6. Event-Driven Time-Domain Behavioral Modeling of Phase-Locked Loops7. Verifying Digitally-Assisted Analog Designs8. Mixed-Signal Physical Implementation Methodology9. Electrically-Aware Design Methodologies for Advanced Process Nodes10. IC Package Co-Design for Mixed-Signal Designs11. Data Management for Mixed-Signal Designs
I directed questions to the following authors, all from Cadence:
Q: What were your contributions to the book?
Nizic: I managed the entire project from the beginning. I created the outline and enlisted the other authors to contribute their chapters. I wrote chapters 1 and 2 and parts of chapter 8.
Bhattacharya: I work on various aspects of mixed-signal verification. For the book, I partnered with Don O'Riordan [Cadence] and wrote chapter 4 about the mixed-signal verification methodology.
White: I co-authored the chapter on electrically-aware design, which examines what's required for analog/mixed-signal design at 20nm and beyond.
McMahon: I'm primarily responsible for developing and testing flows for custom IC design. I made contributions to the mixed-signal physical implementation methodology chapter.
Q: Why is there a need for this book?
Nizic: We at Cadence have been advocating a new methodology shift in mixed-signal design. We believe that the complexity of modern mixed-signal designs, coupled with the high level of integration at advanced nodes, really requires a re-thinking of the traditional mixed-signal methodology. We positioned this book to help guide analog and digital engineers to look beyond traditional methodologies and to enhance their design flows to meet the challenges of modern mixed-signal designs.
There are books out there that go deep into various topics in mixed-signal design, but until now, there were really no books that are focused on the methodology itself.
Q: Could a digital designer who doesn't know much about analog benefit from this book?
Nizic: Absolutely. One of the goals of the book is to enable people from different domains to learn about other domains. They don't need to be experts in other areas but they should at least understand them at some level, so they can collaborate better with those with different skills.
Q: How are analog and digital design and verification roles changing?
Bhattacharya: What we see today is that there are analog verification engineers, and there are digital verification engineers, but there is no official position for mixed-signal verification engineers. We need a position for verification engineers whose expertise is in the mixed-signal world. Perhaps the book will encourage some people to go into mixed-signal verification as a career.
Q: Prabal, what message are you trying to get across in your mixed-signal verification chapter?
Bhattacharya: The message we're trying to send is that the days of isolation for analog and digital verification are over. We really should join hands to create a uniform spectrum all the way from pure digital functional verification down to analog performance verification. These worlds each have their own needs, but they need to communicate with each other to create a full picture of verification.
Q: David, what are you trying to accomplish with the electrically-aware design chapter?
White: Right now in the custom design flow, the electrical impact of physical design decisions cannot be assessed until the full layout is complete. This often causes a series of iterations back through physical design and verification. The ideal solution would be to electrically verify the performance and reliability of every single physical design decision such that the layout is electrically correct by construction, and optimized to meet designer intent.
The term "electrically aware" implies that at any point during physical design you can electrically simulate or observe the impact of a given physical design decision and verify that design intent or electrical rules are met. After several years of interacting with our customer base in dealing with these issues, and now working on 20nm hurdles, we felt we were in a qualified position to write this chapter.
Q: And Jim, what are you emphasizing in the physical implementation chapter?
McMahon: We're saying that new tools and methodologies are required in order to maintain IC designer productivity, mitigate risks, and maintain development schedules. We introduce the concept of capturing design intent and show how it can facilitate increased automation throughout the design flow, and allow correct-by-construction realization of mixed-signal designs. We also show how industry standard formats such as OpenAccess allow analog and digital implementation tools to work directly from a common shared database without time-consuming translations.
Q: Mladen, any concluding remarks?
Nizic: Mixed-signal challenges are getting harder and harder. They won't get any easier. It's time to change, time to look out of the box and explore new methodologies, and time to partner and collaborate within the design team and along the design chain to embrace the new methodology we are suggesting.
Note: For ordering information about the Mixed-Signal Methodology Guide, click here.
Lead authors of the Mixed-Signal Methodology Guide
Prabal Bhattacharya, R&D architect, CadenceJess Chen, principal engineer/manager, QualcommMichael Henrie, software engineering manager, ClioSoftTaranjit Kukal, R&D architect, CadenceJim McMahon, product engineer, CadenceMonte Mar, Boeing Mladen Nizic, director of mixed-signal solution marketing, CadenceRon Vogelsong, analog/mixed-signal model development, CadenceDon O'Riordan, senior architect, CadenceArt Schaldenbrand, senior technical leader, CadenceDavid White, director of R&D for electrically-aware design products, Cadence