Two new approaches to analogue synthesis

Systems design combining SoCs with customer-assembled embedded systems has long been a challenge, says Ian Macbeth, CTO and Vice President Engineering at Anadigm.

Systems design combining SoCs with customer-assembled embedded systems has long been a challenge, one that resists methodologies such as synthesis-based flows, software-based design integration and higher levels of abstraction.

Now, however, innovations in system design have made it possible to integrate these concepts into practical design applications.

Among the innovations that allow engineers to implement analogue design through software are "correct by analysis" and "correct by construction," two new approaches that are rapidly gaining currency within the industry.

To lower the cost of mask sets, SoC design must involve a physical analysis.

Building toward a "correct by analysis" approach to analogue design for ASICs and SoCs, companies including Barcelona Design and Analog Design Automation (ADA) have introduced new tactics in high-level design entry with software-based optimisation and synthesis.

Through these methods, the synthesis process has been expanded to encompass analytical design verification.

The "correct by analysis" approach addresses circuit construction and tuning on the component level, relying on a highly iterative, rule-based method that uses advanced design knowledge and/or stochastic or targeted search algorithms to enable design construction and modification.

Figures of merit for a given analogue design relative to user specifications normally are established through extensive circuit simulation.

Using this design approach the designer can be more discerning, since it typically yields a much larger solution 'set' in much less time than traditional approaches.

The second innovative approach to analogue design depends on programmable analogue circuits, including the latest-generation field programmable analogue arrays (FPAAs).

These exceptionally versatile circuits leverage the precision and flexibility integral to switched-capacitor technology in the design of analogue ICs.

Resembling FPGA circuit design in many ways, FPAAs offer the same low costs for transitioning to silicon and a similar design strategy using configuration data to enable assembly with preverified components.

This "correct by construction" approach uses software-based functional building blocks to construct complex analogue circuits.

Circuits are built through an EDA tool that enables dragging and dropping of these "configurable analogue modules" (CAMs), each of which consists of rules for circuit construction and tuning algorithms to realise a given analogue functional block using the elements within the FPAA.

Because both the FPAA substructure and the CAMs are preverified, they may be deployed freely in software to construct a user application - hence the term "correct by construction" - and manipulate it in real time.

Both "correct by analysis" and "correct by construction" are design innovations that hold great significance for analogue systems.

With design flows that do not rely on manual intervention at the implementation stage, these approaches have provided analogue designer with a new capacity for abstraction, higher-level synthesis, and - for FPAAs - reconfiguration using software.

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