Date: Tuesday 25 March 2014
Time: 11:30 - 13:00
Location / Room: Konferenz 2

Chair:
Georges Gielen, KU Leuven, BE

Co-Chair:
Günhan Dündar, Bogazici University, TR

The session addresses complex challenges in analogue and mixed-signal modeling and design. The regular papers present a novel, zonotope based approach to non-linear macromodeling and a new layout technique in analogue IC design that avoids failures due to IR-drop and electromigration. The two short papers discuss new mechanisms to select solutions from multi-dimensional Pareto-optimal fronts and efficient recording of activities in CMOS neural networks.

Time	Label	Presentation Title Authors
11:30	2.4.1	ELECTROMIGRATION-AWARE AND IR-DROP AVOIDANCE ROUTING IN ANALOG MULTIPORT TERMINAL STRUCTURES Speakers: Ricardo Martins, Nuno Lourenco, António Canelas and Nuno Horta, Instituto de Telecomunicações, Instituto Superior Técnico – TU Lisbon, PT Abstract This paper describes an electromigration-aware and IR-Drop avoidance routing approach considering multiport multiterminal (MP/MT) signal nets of analog integrated circuits (IC). The effects of current densities and temperature in the interconnects may cause the malfunction/failure of a circuit due to IR-Drop or electromigration (EM). These become increasingly more relevant with the ongoing reduction on circuit sizes caused by the evolution of the nanoscale integration processes. Therefore, EM and IR-Drop effects must be taken into account in the design of both power networks and signal wires of analog and mixed-signal ICs, to make their impact on the circuits' reliability negligible. In previous EM and IR-Drop-aware analog IC routing approaches, 'dot-models' are assumed for the terminals, i.e., each terminal has only one port that need to be routed, however, in practice, analog standard cells usually contain multiple electrically-equivalent locations, often distributed over different fabrications layers, where legal connections can be made, i.e., MP terminals, which need to be properly explored. The design flow is detailed, and the applicability of the approach is demonstrated with experimental results, and also, by generating the routing of an analog circuit structure for the UMC 130nm design process.
12:00	2.4.2	(Best Paper Award Candidate) ZONOTOPE-BASED NONLINEAR MODEL ORDER REDUCTION FOR FAST PERFORMANCE BOUND ANALYSIS OF ANALOG CIRCUITS WITH MULTIPLE-INTERVAL-VALUED PARAMETER VARIATIONS Speakers: Yang Song, Sai Manoj Pd and Hao Yu, Nanyang Technological University, SG Abstract It is challenging to efficiently evaluate performance bound of high-precision analog circuits with multiple parameter variations at nano-scale. In this paper, a nonlinear model order reduction is proposed to deploy zonotope-based model for multiple-interval-valued parameter variations. As such, one can have a zonotope-based reachability analysis to generate a set of trajectories with performance bound defined. By further constructing local parameterized subspaces to approximate a number of zonotopes along the set of trajectories, one can perform nonlinear model order reduction to generate the performance bound under parameter variations. As shown by numerical experiments, the zonotope-based nonlinear macromodeling by order of 19 achieves up to 500x speedup when compared to Monte Carlo simulations of the original model; and up to 50% smaller error when compared to previous parameterized nonlinear macromodeling under the same order.
12:30	2.4.3	IMPLEMENTATION ISSUES IN THE HIERARCHICAL COMPOSITION OF PERFORMANCE MODELS OF ANALOG CIRCUITS Speakers: Manuel Velasco-Jiménez, Rafael Castro-López, Elisenda Roca and Francisco Fernández, IMSE-CNM, CSIC and Universidad de Sevilla, ES Abstract Emerging hierarchical design methodologies based on the use of Pareto-optimal fronts (PoFs) are promising candidates to reduce the bottleneck caused by the design of complex analog circuits. However, little work has been reported about how to transmit the information provided by the PoFs of low hierarchical level blocks through the hierarchy to compose the performance models of higher level blocks. This composition actually poses several problems such as the dependence of the PoF performances on the surrounding circuitry and the complexity of dealing with multi-dimensional PoFs in order to explore more efficiently the design space. To deal with these problems, this paper proposes new mechanisms to represent and select candidate solutions from multi-dimensional PoFs that are transformed to the changing operating conditions enforced by the surrounding circuitry. These mechanisms are demonstrated with the generation of the performance model of an active filter by composing previously generated PoFs of operational amplifiers.
12:45	2.4.4	MODELING OF AN ANALOG RECORDING SYSTEM DESIGN FOR ECOG AND AP SIGNALS Speakers: Nils Heidmann1, Nico Hellwege1, Tim Hoehlein1, Thomas Westphal1, Dagmar Peters-Drolshagen1 and Steffen Paul2 1University of Bremen, DE; 2University Bremen, DE Abstract The recording of neural activities has turned out to be a promising approach to understand the basic function of specific brain parts like the visual or motor cortex. However, the development and design of advanced neural recording systems is very challenging since the number of parallel measurement channels increases continuously. Beside the analog recording channels digital preprocessing becomes mandatory to handle the corresponding amount of data and to adapt this data to the available transmission bandwidth. In this paper we present the design as well as the behavioral modeling of an analog recording front-end. Simulation and measurement results demonstrate the performances of the system for recording neural signals. Since simulation of this analog front-end is very time consuming but essential for large fully-integrated designs, a mixed-signal model approach is introduced that enables a significant simulation acceleration of integrated and external analog front-ends. The simulation can be accelerated by a factor of up to 22.2 for a single front-end. The proposed system has been fabricated in a 0.35 µm CMOS technology and performances have been measured. This demonstrates that the behavioral model is compatible to the transistor level design. A neural spike detector shows the transient performance of the modeled design on real input stimuli.
13:00	IP1-3, 411	MODEL BASED HIERARCHICAL OPTIMIZATION STRATEGIES FOR ANALOG DESIGN AUTOMATION Speakers: Engin Afacan1, Gunhan Dundar1, Faik Baskaya1, Simge Ay1 and Francisco Fernandez2 1Bogazici University, TR; 2Universidad de Sevilla, TR Abstract The design of complex analog circuits by using flat optimization-based approaches is inefficient, even impossible, due to the high number of design variables and the growth of the cost of performance evaluation with the circuit size. Over the past two decades, top-down hierarchical design approaches have been developed and applied. They are based on hierarchical circuit decomposition and specification transmission from top-level to lower level blocks. However, such specification transmission is usually performed with little knowledge on the feasibility of the specifications, leading, therefore, to costly redesign iterations. Even if the specification transmission is successful, there is no guarantee that it is optimal in terms of e.g., power consumption or area occupation. To palliate this problem, two novel model-based hierarchical synthesis methods are proposed in this paper: Model-Based Hierarchical Optimization (MBHO) and Improved Model-Based Hierarchical Optimization (IMBHO). They are based on the concurrent design at higher and lower hierarchical levels and appropriate communication between the different processes. Experimental results on a filter example comparing the new approaches and the conventional top-down design approach are provided.
13:01	IP1-4, 925	A NOVEL LOW POWER 11-BIT HYBRID ADC USING FLASH AND DELAY LINE ARCHITECTURES Speakers: Hsun-Cheng Lee and Jacob Abraham, the University of Texas at Austin, US Abstract This paper presents a novel low power 11-bit hybrid ADC using flash and delay line architectures, where a 4-bit flash ADC is followed by a 7-bit delay-line ADC. This hybrid ADC inherits accuracy and power efficiency from flash ADCs and delay-line ADCs, respectively. Also, in order to reduce the power of the first stage flash ADC, a power-saving technique is adopted by biasing the DC tail current of the pre-amplifiers at 5μA instead of the operational current, 47μA in stand-by mode. The hybrid ADC was designed and simulated in a commercial 65nm process. With a 1.1 V supply and 100 MS/s, the ADC achieves an SNDR of 60 dB and consumes 1.6 mW, which results in a figure of merit (FOM) of 19.4 fJ/conversion-step without any calibration technique. Also, Monte Carlo simulations are performed with a 3σ device mismatch for the SNDR estimation, and the SNDR is observed to be better than 58.5 dB.
13:02	IP1-5, 752	SEMI-SYMBOLIC ANALYSIS OF MIXED-SIGNAL SYSTEMS INCLUDING DISCONTINUITIES Speakers: Carna Radojicic, Christoph Grimm, Javier Moreno and Xiao Pan, TU Kaiserslautern, DE Abstract The paper describes an approach for semi-symbolic analysis of mixed-signal systems that contain discontinuous functions, e.g. due to modeling comparators. For modeling and semi- symbolic simulation, we use extended Affine Arithmetic. Affine Arithmetic is currently limited to accurate analysis of linear func- tions and mild non-linear functions, but not yet discontinuities. In this paper we extend the approach to also handle discontinuities. For demonstration, we symbolically analyze a Σ∆-modulator.
13:03	IP1-6, 927	(Best Paper Award Candidate) NOVEL CIRCUIT TOPOLOGY SYNTHESIS METHOD USING CIRCUIT FEATURE MINING AND SYMBOLIC COMPARISON Speakers: Cristian Ferent and Alex Doboli, Stony Brook University, US Abstract This paper presents a reasoning-based approach to analog circuit synthesis using ordered node clustering representations (ONCR) to describe alternative circuit features and symbolic circuit comparison to characterize performance trade-offs of synthesized solutions. Case studies illustrate application of the proposed methods to topology selection and refinement.
13:04	IP1-7, 468	AN EMBEDDED OFFSET AND GAIN INSTRUMENT FOR OPAMP IPS Speakers: Jinbo Wan and Hans KerkHoff, CAES-TDT, CTIT, University of Twente, NL Abstract Analog and mixed-signal IPs are increasingly required to use digital fabrication technologies and are deeply embedded into system-on-chips (SoC). These developments append more requirements and challenges on analog testing methodologies. Traditional analog testing methods suffer from less accessibility and control with regard to these embedded analog circuits in SoCs. As an alternative, an embedded instrument for analog OpAmp IP tests is proposed in this paper. It can provide the exact gain and offset values of OpAmps instead of only pass/fail result. What's more, it is an non-invasive monitor and can work online without isolating the DUT Opamp from its surrounding feedback networks. Nor does it require accurate test stimulations. In addition, the monitor can remove its own offsets without additional complex self-calibration circuits. All self-calibrations are completed in the digital domain after each measurement in real time. Therefore it is also suitable for aging-sensitive applications, in which the monitor may suffer from aging mechanisms and has additional offset drifts as well. The monitor measurement range for offset is from 0.2mV to 70mV, and for gain it is from 0dB to 40dB. The error for offset measurements can be 10% of the measurement value with plus/minus 0.1mV, and -2.5dB for gain measurements.
13:00		End of session Lunch Break in Exhibition Area Sandwich lunch