Ivano Adolfo Maio

M/spl pi/log, macromodeling via parametric identification of logic gates

This paper addresses the development of computational models of digital integrated circuit input and output buffers via the identification of nonlinear parametric models. The obtained models run in standard circuit simulation environments, offer improved accuracy and good numerical efficiency, and do not disclose information on the structure of the modeled devices. The paper reviews the basics of the parametric identification approach and illustrates its most recent extensions to handle temperature and supply voltage variations as well as power supply ports and tristate devices.

Analysis of crosstalk and field coupling to lossy MTLs in a SPICE environment

This paper proposes a circuit model for lossy multiconductor transmission lines (MTLs) suitable for implementation in modern SPICE simulators, as well as in any simulator supporting differential operators. The model includes the effects of a uniform or nonuniform disturbing field illuminating the line and is especially devised for the transient simulation of electrically long wideband interconnects with frequency dependent per-unit-length parameters. The MTL is characterized by its transient matched scattering responses, which are computed including both dc and skin losses by means of a specific algorithm for the inversion of the Laplace transform. The line characteristics are then represented in terms of differential operators and ideal delays to improve the numerical efficiency and to simplify the coding of the model in existing simulators. The model can be successfully applied to many kinds of interconnects ranging from micrometric high-resistivity metallizations to low-loss PCBs and cables, and can be considered a practical extension of the widely appreciated lossless MTL SPICE model, which maintains the simplicity and efficiency.

Modeling of multiconductor buses and analysis of crosstalk, propagation delay and pulse distortion in high speed GaAs logic circuits

Crosstalk, propagation delay, pulse distortion in multiconductor buses for high-speed GaAs logic circuits are analyzed. A simple but accurate quasi-TEM model of the bus is developed, and a critical analysis is carried out both on the accuracy of different approximate lumped and distributed models and on the impact of such approximations on the time-domain response. Results on the behavior of multiconductor buses in the presence of realistic input waveforms, are presented and design criteria are obtained. >

Behavioral models of I/O ports from measured transient waveforms

This paper addresses the development of accurate and efficient behavioral models of digital integrated circuit ports from measured transient responses. The proposed approach is based on the estimation of parametric models from port voltage and current waveforms. The modeling process is described and applied to the modeling of output ports. Its feasibility is demonstrated by the identification of a real device from actual measurements, and by the comparison of the predicted device response with the measured one.

Parametric macromodels of differential drivers and receivers

This paper addresses the modeling of differential drivers and receivers for the analog simulation of high-speed interconnection systems. The proposed models are based on mathematical expressions, whose parameters can be estimated from the transient responses of the modeled devices. The advantages of this macromodeling approach are: improved accuracy with respect to models based on simplified equivalent circuits of devices; improved numerical efficiency with respect to detailed transistor-level models of devices; hiding of the internal structure of devices; straightforward circuit interpretation; or implementations in analog mixed-signal simulators. The proposed methodology is demonstrated on example devices and is applied to the prediction of transient waveforms and eye diagrams of a typical low-voltage differential signaling (LVDS) data link.

Influence of the line characterization on the transient analysis of nonlinearly loaded lossy transmission lines

The analysis of nonlinearly terminated lossy transmission lines is addressed in this paper with a modified version of a method belonging to the class of mixed techniques, which characterize the line in the frequency domain and solve the nonlinear problem in the time domain via a convolution operation. This formulation is based on voltage wave variables defined in the load sections. The physical meaning of such quantities helps to explain the transient scattering process in the line and allows us to discover the importance (so far often overlooked) of the reference impedance used to define the scattering parameters. The complexity of the transient impulse responses, the efficiency of the algorithms, and the precision of the results are shown to be substantially conditioned by the choice of the reference impedance. The optimum value of the reference impedance depends on the amount of line losses. We show that a low-loss line can be effectively described if its characteristic impedance or the characteristic impedance of the associated LC line is chosen as the reference impedance. Based on the physical interpretation of our formulation, we are able to validate the numerical results, and to demonstrate that, despite claimed differences or improvements, the formulations of several mixed methods are fundamentally equivalent. >

Reliable eye-diagram analysis of data links via device macromodels

This paper addresses the impact of device macromodels on the accuracy of signal integrity and performance predictions for critical digital interconnecting systems. It exploits nonlinear parametric models for both single-ended and differential devices, including the effects of power supply fluctuations and receiver bit detection. The analysis demonstrates that the use of well-designed macromodels dramatically speeds up the simulation as well it preserves timing accuracy even for long bit sequences.

Behavioral models of digital IC ports from measured transient waveforms

This paper addresses the behavioral modeling of output ports of digital integrated circuits via the identification of nonlinear parametric models. The aim of the approach is to produce models for signal integrity (SI) simulation directly from the measured transient responses of the devices. The modeling process is thoroughly described and an experimental demonstration of its feasibility is given.

On the behavioral modeling of integrated circuit output buffers

The properties of common behavioral macromodels for single ended CMOS integrated circuits output buffers are discussed with the aim of providing criteria for an effective use of possible modeling options.

Transient field coupling and crosstalk in lossy lines with arbitrary loads

We extend the transient scattering analysis of a lossy multiconductor transmission line to the evaluation of the interference produced by a field illuminating the line. The external interference is described by suitable voltage wave sources that are readily computed in the time domain and do not affect the structure of the transient scattering equations. The proposed formulation fully exploits the advantages of the transient analysis based on the line matched scattering parameters, dealing effectively with low-loss lines and helping the understanding of the interference mechanism through the physical interpretation of the results. The simplicity and efficiency of our approach is evidenced by means of a numerical example of the external interferences on a realistic nonlinearly loaded highly mismatched 3-conductor interconnect.