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23
MAELSTROM: Efficient simulationbased synthesis for custom analog cells
 Proc. of the 1999 ACM/IEEE Design Automation Conference
, 1999
"... Analog synthesis tools have failed to migrate into mainstream use primarily because of difficulties in reconciling the simplified models required for synthesis with the industrialstrength simulation environments required for validation. MAELSTROM is a new approach that synthesizes a circuit using t ..."
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Cited by 27 (6 self)
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Analog synthesis tools have failed to migrate into mainstream use primarily because of difficulties in reconciling the simplified models required for synthesis with the industrialstrength simulation environments required for validation. MAELSTROM is a new approach that synthesizes a circuit using the same simulation environment created to validate the circuit. We introduce a novel genetic/ annealing optimizer, and leverage network parallelism to achieve efficient simulatorintheloop analog synthesis. ___________________________ Permission to make digital/hardcopy of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage, the copyright notice, the title of the publication and its date appear, and notice is given that copying is by permission of ACM, Inc. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee.
Canonical Symbolic Analysis of Large Analog Circuits with Determinant Decision Diagrams
 IEEE TRANS. ON COMPUTERAIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS
, 2000
"... Symbolic analogcircuit analysis has many applications, and is especially useful for analog synthesis and testability analysis. Existing approaches rely on two forms of symbolic expression representation: expanded sumofproduct form or arbitrarily nested form. Expanded form suffers the problem that ..."
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Cited by 17 (5 self)
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Symbolic analogcircuit analysis has many applications, and is especially useful for analog synthesis and testability analysis. Existing approaches rely on two forms of symbolic expression representation: expanded sumofproduct form or arbitrarily nested form. Expanded form suffers the problem that the number of product terms grows exponentially with the size of a circuit, and approximation has to be used. Nested form is not canonical, i.e., many representations exist for a symbolic expression, and manipulations with the nested form are often complicated. In this paper, we present a new approach to exact and canonical symbolic analysis by exploiting the sparsity and sharing of product terms. It consists of representing the symbolic determinant of a circuit matrix by a graphcalled determinant decision diagram (DDD)and performing symbolic analysis by graph manipulations. We showed that DDD construction, as well as many symbolic analysis algorithms, can be performed in time complex...
Hierarchical Symbolic Analysis Of Large Analog Circuits With Determinant Decision Diagrams
 IEEE Trans. on ComputerAided Design of Integrated Circuits and Systems
, 1998
"... A novel hierarchical approach is proposed to symbolic analysis of large analog circuits. The key idea is to use a graphbased representation  called Determinant Decision Diagram (DDD)  to represent the symbolic determinant and cofactors associated with the MNA matrix for each subcircuit block. B ..."
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Cited by 14 (4 self)
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A novel hierarchical approach is proposed to symbolic analysis of large analog circuits. The key idea is to use a graphbased representation  called Determinant Decision Diagram (DDD)  to represent the symbolic determinant and cofactors associated with the MNA matrix for each subcircuit block. By exploiting the inherent sharing and sparsity of symbolic expressions, DDD is capable of representing a huge number of symbolic product terms in a canonical and highlycompact manner. Further, it enables cofactoring and sensitivity computation to be performed with time linear in the size of DDD. Experimental results have demonstrated that our method outperforms the bestknown existing hierarchical symbolic analyzer SCAPP, and sometimes even numerical simulator SPICE.
Symbolic Analysis of Large Analog Circuits with Determinant Decision Diagrams
, 1997
"... Symbolic analogcircuit analysis has many applications, and is especially useful for analog synthesis and testability analysis. In this paper, we present a new approach to exact and canonical symbolic analysis by exploiting the sparsity and sharing of product terms. It consists of representing the s ..."
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Cited by 13 (8 self)
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Symbolic analogcircuit analysis has many applications, and is especially useful for analog synthesis and testability analysis. In this paper, we present a new approach to exact and canonical symbolic analysis by exploiting the sparsity and sharing of product terms. It consists of representing the symbolic determinant of a circuit matrix by a graphcalled determinant decision diagram (DDD)and performing symbolic analysis by graph manipulations. We showed that DDD construction and DDDbased symbolic analysis can be performed in time complexity proportional to the number of DDD vertices. We described a vertex ordering heuristic, and showed that the number of DDD vertices can be quite smallusually ordersofmagnitude less than the number of product terms. The algorithm has been implemented. An orderofmagnitude improvement in both CPU time and memory usages over existing symbolic analyzers ISAAC and MapleV has been observed for large analog circuits. 1. Introduction Symbolic a...
ASF: A practical simulationbased methodology for the synthesis of custom analog circuits
 IEEE/ACM Int. Conf. on Computer Aided Design
, 2001
"... Abstract: This paper describes ASF, a novel celllevel analog synthesis framework that can size and bias a given circuit topology subject to a set of performance objectives and a manufacturing process. To manage complexity and timetomarket, SoC designs require a high level of automation and reuse. ..."
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Cited by 9 (1 self)
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Abstract: This paper describes ASF, a novel celllevel analog synthesis framework that can size and bias a given circuit topology subject to a set of performance objectives and a manufacturing process. To manage complexity and timetomarket, SoC designs require a high level of automation and reuse. Digital methodologies are inapplicable to analog IP, which relies on tight control of lowlevel device and circuit properties that vary widely across manufacturing processes. This analog synthesis solution automates these tedious, technology specific aspects of analog design. Unlike previously proposed approaches, ASF extends the prevalent “schematic and SPICE ” methodology used to design analog and mixedsignal circuits. ASF is topology and technology independent and can be easily integrated into a commercial schematic capture design environment. Furthermore, ASF employs a novel numerical optimization formulation that incorporates classical downhill techniques into stochastic search. ASF consistently produces results comparable to expert manual design with 10x fewer candidate solution evaluations than previously published approaches that rely on traditional stochastic optimization methods. I.
A Case Study of Synthesis for IndustrialScale Analog IP: Redesign of the Equalizer/Filter Frontend for an ADSL CODEC
 In Proc. Design Automation Conf
, 2000
"... A persistent criticism of analog synthesis techniques is that they cannot cope with the complexity of realistic industrial designs, especially systemlevel designs. We show how recent advances in simulationbased synthesis can be augmented, via appropriate macromodeling, to attack complex analog blo ..."
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Cited by 7 (3 self)
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A persistent criticism of analog synthesis techniques is that they cannot cope with the complexity of realistic industrial designs, especially systemlevel designs. We show how recent advances in simulationbased synthesis can be augmented, via appropriate macromodeling, to attack complex analog blocks. To support this claim, we resynthesize from scratch, in several different styles, a complex equalizer/filter block from the frontend of a commercial ADSL CODEC, and verify by full simulation that it matches its original design specifications. As a result, we argue that synthesis has significant potential in both custom and analog IP reuse scenarios.
Efficient Derivation of Exact sExpanded Symbolic Expressions for Behavioral Modeling of Analog Circuits
, 1998
"... This paper presents an efficient method for deriving exact sexpanded symbolic expressions for behavioral modeling of analog circuits. The key idea is to introduce a graphbased representation called multiroot Determinant Decision Diagram (DDD), where each root represents the symbolic coefficient o ..."
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Cited by 6 (5 self)
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This paper presents an efficient method for deriving exact sexpanded symbolic expressions for behavioral modeling of analog circuits. The key idea is to introduce a graphbased representation called multiroot Determinant Decision Diagram (DDD), where each root represents the symbolic coefficient of a particular power of s. By exploiting sharing and sparsity, a huge number of symbolic product terms can be compactly represented and efficiently manipulated. Experimental results have demonstrated that this method can produce the exact sexpandedsymbolic transfer function for ¯A741 opamps in several CPU seconds on a UltraSparcI workstation, and the use of generated symbolic expression for frequencydomain simulation achieved a speedup of about 50 over SPICE3F5. I. Introduction Symbolic analysis is to calculate the behavior or the characteristic of a circuit in terms of symbolic parameters. Due to its importance in many applications such as optimum topology selection, design space explo...
Constructing Symbolic Models for the Input/Output Behavior of Periodically TimeVarying Systems Using Harmonic Transfer Matrices
, 2002
"... A new technique is presented for generating symbolic expressions for the harmonic transfer functions of linear periodically timevarying (LPTV) systems, like mixers and PLL's. The algorithm, which we call Symbolic HTM, is based on the organisation of the harmonic transfer functions into a harmonic t ..."
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Cited by 3 (0 self)
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A new technique is presented for generating symbolic expressions for the harmonic transfer functions of linear periodically timevarying (LPTV) systems, like mixers and PLL's. The algorithm, which we call Symbolic HTM, is based on the organisation of the harmonic transfer functions into a harmonic transfer matrix. This representation allows to manipulate LPTV systems in a way that is similar to linear timeinvariant (LTI) systems, making it possible to generate symbolic expressions which relate the overall harmonic transfer functions to the characteristics of the building blocks. These expressions can be used as design equations or as parametrized models for use in simulations. The algorithm is illustrated for a downconversion mixer.
Hierarchical Symbolic Analysis of Analog Integrated Circuits via Determinant Decision Diagrams
 IEEE Transactions on ComputerAided Design of Integrated Circuits and Systems, Vol.19, Apr 2000
, 2000
"... A new approach is proposed to hierarchical symbolic analysis of large analog integrated circuits. It consists of performing symbolic suppression of each subcircuit to its terminals in terms of subcircuit matrix determinants and cofactors, and applying Cramer's rule to solve symbolically the set of e ..."
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Cited by 2 (0 self)
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A new approach is proposed to hierarchical symbolic analysis of large analog integrated circuits. It consists of performing symbolic suppression of each subcircuit to its terminals in terms of subcircuit matrix determinants and cofactors, and applying Cramer's rule to solve symbolically the set of equations at the top level of the circuit hierarchy. The novelty of the proposed approach is to use an annotated, directed and acyclic graph, called Determinant Decision Diagram (DDD), to represent symbolic determinants of subcircuit matrices and cofactors used in subcircuit suppression, as well as symbolic determinants of the toplevel circuit matrix and cofactors required in applying Cramer's rule. DDD enables systematically exploiting the inherent sparsity of circuit matrices and the sharing of symbolic expressions. It is capable of representing a huge number of symbolic product terms in a canonical and highly compact manner. The proposed approach is illustrated using a Cauer parameter low...
Hierarchical approach to exact symbolic analysis of large analog circuits
 in Proc. Design Automation Conf. (DAC
, 2004
"... Abstract—This paper proposes a novel approach to the exact symbolic analysis of very large analog circuits. The new method is based on determinant decision diagrams (DDDs) representing symbolic product terms. But instead of constructing DDD graphs directly from a flat circuit matrix, the new method ..."
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Cited by 2 (2 self)
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Abstract—This paper proposes a novel approach to the exact symbolic analysis of very large analog circuits. The new method is based on determinant decision diagrams (DDDs) representing symbolic product terms. But instead of constructing DDD graphs directly from a flat circuit matrix, the new method constructs DDD graphs in a hierarchical way based on hierarchically defined circuit structures. The resulting algorithm can analyze much larger analog circuits exactly than before. The authors show that exact symbolic expressions of a circuit are cancellationfree expressions when the circuit is analyzed hierarchically. With this, the authors propose a novel symbolic decancellation process, which essentially leads to the hierarchical DDD graph constructions. The new algorithm partially avoids the exponential DDD construction time by employing more efficient DDD graph operations during the hierarchical construction. The experimental results show that very large analog circuits, which cannot be analyzed exactly before like UPS and other unstructured circuits up to 100 nodes, can be analyzed by the new approach for the first time. The new approach significantly improves the exact symbolic capacity and promises huge potentials for the applications of exact symbolic analysis. Index Terms—Behavioral modeling, circuit simulation, symbolic analysis. I.