Circuit Synthesis and Web-Based Design Reaches the Analog World
by Earl Reinkensmeyer

Barcelona Design Systems of Mountain View, California, has begun a Web-based design service for experimental design synthesis of analog circuits. If you are satisfied with the design, you may download a SPICE netlist for a fee. If you have already registered as a user and have $2,500 deposited by credit card, you may download your design immediately. In this article we describe Barcelona's design service and provide an update on Antrim Design Systems' analog design synthesis product. Antrim-MSS has just been released at this writing to complement Antrim's mixed-signal simulation, characterization, and library calibration products.

Digital circuit synthesis took the chip design community by storm over ten years ago. Few, if any, custom, ASIC, or PLD designs are developed outside of the design synthesis process. Solutions for analog circuit synthesis have not been available until recently.

If a chip is to contain extensive analog circuitry, the analog designer or design team typically designs at the circuit and device level, possibly reapplying some circuits from previous designs. If digital logic is present on such a chip, it may be designed at the circuit or gate levels, or with a relatively small group of standard cells. If the chip is big "D" (much digital) and little "a," the digital and analog designers are applying vastly different design techniques or methodologies, that is, until the recent availability of design services and tools from Antrim and Barcelona.

As will be described later, the two available analog synthesis approaches offer the user different approaches for specifying the design and evaluating the synthesis results. The analog synthesis processes still entail more trade-off analysis than digital logic synthesis. However, the new tools both bring digital and analog design methodologies a bit closer together. Even though the underlying design of digital semiconductor circuits depends upon analog circuit design for a given fabrication process, until recently, digital chip designers have not been required to incorporate analog circuit design solutions in their work.

With deep submicron technologies, the digital designer is confronted with a number of analog circuit effects. See the article "Optimizing Your Design Environment." Developers of digital design tools are now challenged to solve these analog circuit effects to maintain the very successful and expeditious "digital like" design methodology. RF circuit designers have all along solved analog effects for their high-speed circuits.

The ever-increasing need for analog technology in the rapidly growing communication and automotive product development arenas has provided more of a demand for EDA solutions that help speed the design of analog and mixed-mode circuits. In this article, I will summarize two of the most recent developments.

Barcelona Design Systems

Barcelona is offering a Web-based design service to synthesize analog and mixed-signal circuits. Picasso, the op-amp tool, is available for design application, and the Dali RF Passives Optimizer is at this writing available for free trial. Design services with tools to design phase-locked loops and other analog circuits will likely become available soon.

With a standard browser, users access Barcelona's Web site and specify the fab and process for the op amp. The system then presents the user with performance specifications, including default values for each parameter. Designers select the overall goal -- for example, maximize slew rate or minimize quiescent power -- of the design, and change the parameters as they see fit. Once satisfied, they send that request to the Barcelona server farm, which sends back results in less than a minute. If the design is not feasible, Barcelona will suggest which parameters need to be relaxed in order to become feasible. As part of the service, Barcelona offers users the ability to run a SPICE simulation right on the site. Finally, the service provides a netlist for the design. More than fifty different op-amp types are supported.

The company's Dali RF Passives Optimizer provides a synthesis and optimization capability for the design of passive components such as inductors and resonators, which are commonly used in analog and RF circuitry. Using simple forms to specify various performance requirements, constraints, and electrical parameters (e.g., area, spacing, width, inductance, tank impedance, etc.), the designer can perform a trade-off analysis based on near real-time feedback from the technology. Dali provides the designer with the sensitvity of each of its parameter and constraint fields, alerting the designer if certain specifications will significantly impact the overall design objectives.

Dali also offers an analysis and simulation capability through the ASITIC technology developed by Ali Niknejad at the University of California Berkeley. The ASITIC technology is now available on the Barcelona site. ASITIC is an interactive tool that allows an RF circuit engineer to design and simulate inductors and transformers, and facilitates the planning and optimization of the layout of metal structures in the presence of substrate effects.

After an introductory price of $500 for each op-amp SPICE netlist retrieved, the pricing will be from $500 to $2000 per retrieval. At this writing, the pricing for use of the Dali RF Passives Optimizer tool had not been established.

Supported fabs include TSMC, Chartered Semiconductor, AMI, and UMC.

Functions to be added to the service include comparators, bias cells, switched capacitors, and phase-locked loops. A fir filter may be a longer term goal.

Bob Donkin, chief technology officer at Linear Technology, reports that the Picasso Op Amplifier Optimizer worked to his satisfaction.

"Like an interactive data sheet, our design service allows the engineer to design circuits by specifying the circuit's performance. The engine then processes the order, and suggests the optimal circuit design based on the parameters set by the user. And with our Web business model, designers can use the service any time, from any standard browser."
Mar Hershenson, Founder and CEO, Barcelona Design Systems

Antrim Design Systems

Antrim believes that Antrim-MSS analog design synthesis users have the opportunity to create robust designs by employing multiple test bench optimization with Antrim's A/MS simulator and by evaluating all performance measurements of a circuit simultaneously. Antrim-MSS has a learning mode optimizer for quickly adjusting circuit design parameters to resolve conflicting performance goals. A database is created to collect the results of all working circuit configurations. During synthesis to a new set of specifications, the MSS lookup mode is offered to eliminate repetitive circuit simulations. Then, by combining these functions with behavioral synthesis models in Verilog-A/MS, Antrim believes that the user may quickly retarget orders of magnitude faster than in previous SPICE-based methods.

With MSS, the design engineer's synthesis plans capture the design knowledge, thereby providing a mechanism for documenting the steps used to create a design in a form that is re-executable for new processes and performance specifications. The synthesis plans may also be used to train new engineers and provide a mechanism for IP protection. Top-down synthesis of mixed-signal circuits is enabled, providing the capability for engineers to create a working circuit netlist tuned to their specifications without requiring detailed knowledge of the design process.

Before the general release of MSS, Antrim's technology partners have been the initial users.

Mike Demler, Engineering Director, Antrim Design Systems

Conclusion

At this writing, products and services from Antrim Design Systems and Barcelona Design have just been released to the general market and have been in an evaluation phase by initial users. It is expected that these new EDA technologies will require substantial proof and long-term investment before analog designers can apply it across the broad spectrum of their design needs. These are interesting developments that have the potential to provide chip designers with a much-needed edge when compared to the manual analog circuit tuning and iterative simulation steps in use today.

URL References

www.barcelonadesign.com
www.antrim.com

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