- Author:
- Emilian Stephen Ochotta
In contrast to digital ASIC design, design automation tools for the analog portions of mixed-signal ASICs are largely nonexistent: most analog circuitry is still designed by hand. Synthesis of analog cells promises an enticing alternative: fully automatic translation from an un-sized circuit topology to a sized circuit that meets user supplied performance specifications.
We present a new synthesis strategy that can automate fully the path from a circuit topology and performance specifications to a sized circuit schematic. This strategy relies on asymptotic waveform evaluation to predict circuit performance and simulated annealing to solve a novel unconstrained optimization formulation of the circuit synthesis problem. We have implemented this strategy in a pair of tools called ASTRX and OBLX. ASTRX is a circuit compiler that generates a performance prediction module that maps the component and voltage values in the circuit to the performance metrics specified by the user. More exactly, ASTRX generates code that implements a cost function that is carefully constructed so that its minimum value occurs at a circuit design that best meets the input specifications. This cost function code is then compiled and linked to OBLX, which uses simulated annealing to solve numerically for its minimum, thereby designing the circuit.
To show the generality of our new approach, we have used this system to re-synthesize essentially all the analog synthesis benchmarks published in the past decade; ASTRX/OBLX has re-synthesized circuits in an afternoon that, for some prior approaches, had required months. To show the viability of the approach on difficult circuits, we have re-synthesized a recently published (and patented), high-performance operational amplifier; ASTRX/OBLX achieved performance comparable to the expert manual design. And finally, to test the limits of the approach on industrial-sized problems, we have synthesized the component cells of a pipelined A/D converter; ASTRX/OBLX successfully generated cells 2X-3X more complex than any published to date.
Cited By
Dhanwada N, Nunez-Aldana A and Vemuri R Hierarchical constraint transformation using directed interval search for analog system synthesis Proceedings of the conference on Design, automation and test in Europe, (70-es)- Ochotta E, Rutenbar R and Carley L ASTRX/OBLX Proceedings of the 31st annual Design Automation Conference, (24-30)
- Mukherjee T, Carley L and Rutenbar R Synthesis of manufacturable analog circuits Proceedings of the 1994 IEEE/ACM international conference on Computer-aided design, (586-593)
Index Terms
- Synthesis of high-performance analog cells in ASTRX/OBLX
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