Crosstalk delay-noise which occurs due to the simultaneous transitions of victim and aggressor drivers is very sensitive to their mutual alignment. Hence, during static noise analysis, it is crucial to identify the worst-case victim-aggressor alignment which results in the maximum delay-noise. Although several approaches have been proposed to obtain the worst-case aggressor alignment, most of them compute only the worst-case stage delay of the victim. However, in reality it is essential to compute the worst-case combined delay of victim stage and victim receiver gate [5, 9]. We propose a heuristic approach to compute the worst-case aggressor alignment which maximizes the victim receiver output arrival time. In this work, we use a novel cumulative gate overdrive voltage (CGOV ) metric to model the victim receiver output transition. HSPICE simulations, performed on industrial nets to validate the proposed methodology, show an average error of 1.7% in delay-noise when compared to the worst-case alignment obtained by an exhaustive sweeping.

Dynamic CMOS logic circuits are widely employed in high performance VLSI chips in pursuing very high system performance. However, dynamic circuits are inherently less resistant to noises than static CMOS gates. With the increasing stringent noise requirement due to aggressive technology scaling, the noise tolerance of dynamic circuits has to be first improved for the overall reliable operation of VLSI systems. In this paper, we present a novel noise-tolerant design technique using circuitry exhibiting a negative differential resistance effect. We have demonstrated that using the proposed method the noise tolerance of dynamic logic gates can be improved beyond the level of static CMOS logic gates while the performance advantage of dynamic circuits is still retained.

Dynamic CMOS logic circuits are widely employed in high-performance VLSI chips in pursuing very high system performance. However, dynamic CMOS gates are inherently less resistant to noises than static CMOS gates. With the increasing stringent noise requirement due to aggressive technology scaling, the noise tolerance of dynamic circuits has to be first improved for the overall reliable operation of VLSI chips designed using deep submicron process technology. In the literature, a number of design techniques have been proposed to enhance the noise tolerance of dynamic logic gates. An overview and classification of these techniques are first presented in this paper. Then, we introduce a novel noise-tolerant design technique using circuitry exhibiting a negative differential resistance effect. We have demonstrated through analysis and simulation that using the proposed method the noise tolerance of dynamic logic gates can be improved beyond the level of static CMOS logic gates while the performance advantage of dynamic circuits is still retained. Simulation results on large fan-in dynamic CMOS logic gates have shown that, at a supply voltage of 1.6 V, the input noise immunity level can be increased to 0.8 V for about 10% delay overhead and to 1.0 V for only about 20% delay overhead.

In this paper, we propose an accurate and fast method to estimate the crosstalk noise in the presence of multiple aggressor nets for use in physical design automation tools. Since noise estimation is often part of the inner loop of optimization algorithms, very efficient closed-form solutions are needed. Previous approaches model aggressor nets one at a time, assuming that the coupling capacitance to all quiet aggressor nets are grounded. They also model the load from interconnect branches as a lumped capacitor, the value of which is the sum of interconnect and load capacitances of the branch. Finally, previous works typically use simple lumped 2-4-node circuit templates and employ a so-called dominant pole approximation to solve the template circuit. While these approximations allow for very fast analysis, they may result in significant underestimation of the noise. In this paper, we propose a new and more comprehensive fast noise estimation method. We propose a novel reduction technique for modeling quiet aggressor nets based on the concept of coupling point admittance. We also propose a reduction method to replace tree branches with effective capacitors which models the effect of resistive shielding. Furthermore, we model the simplified single aggressor net crosstalk noise problem using a 6-node template circuit and propose a new double pole approach to solve the template circuit. We have tested the proposed method on noise-prone interconnects from an industrial high-performance processor. Our results show a worst case error of 7.8% and an average error of 2.7%, while allowing for very fast analysis.

In this paper, we introduce an application-specific device modeling methodology to develop simple device model that accurately tracks the actual device I-V characteristics in relevant but bounded operating regions. We have specifically used a simple MOSFET model to precisely analyze the switching noises generated on a chip due to simultaneous driving of chip output pads by bulky buffer gates. Previous works in analytical modeling of simultaneous switching noises employed long-channel and /spl alpha/-power law transistor models; however, these models led to complex circuit equations that on truncation caused poor matching between manual analysis and actual simulation results. Also, in order to retain the simplicity of manual analysis, previous researchers ignored the parasitic capacitances of the bonding pads. This paper demonstrates that by using a simple application-specific transistor model, circuit equations can be solved precisely without requiring any gross approximations or model truncations, even when the inductance effects of bonding wires are simultaneously considered along with parasitic capacitances of the output pads. The analytical results derived in this paper tally with HSPICE simulation values within 3% deviations.

Transistor tapering is a widely used technique applied to optimize the geometries of CMOS transistors in high-performance circuit design with a view to minimizing the delay of a FET network. Currently, in a long series-connected FET chain, the dimensions of the transistors are decreased from bottom transistor to the top transistor in a manner where the width of transistors is tapered linearly or exponentially. However, it has not been mathematically proved whether either of these tapering schemes yields optimal results in terms of minimization of switching delays of the network. In this paper, we rigorously analyze MOS circuits consisting of long FET chains under the widely used Elmore delay model and derive the optimality of transistor tapering by employing variational calculus. Specifically, we demonstrate that neither linear nor exponential tapering alone minimizes the discharge time of the FET chain. Instead, a composition of exponential and constant tapering actually optimizes the delay of the network. We have also corroborated our analytical results by performing extensive simulation of FET networks and showing that both analytical and simulation results are always consistent.

In this paper, we study the simultaneous switching noise problem by using an application-specific modeling method. A simple yet accurate MOSFET model is proposed in order to derive closed-form formulas for simultaneous switching noise voltage waveforms. We first derive a simple formula assuming that the inductances are the only parasitics. Through HSPICE simulation, we show that the new formula is more accurate than previous results based on the same assumption. We then study the effect of the parasitic capacitances of ground bonding wires and pads. We show that the maximum simultaneous switching noise should be calculated using four different formulas depending on the value of the parasitic capacitances and the slope of the input signal. The proposed formulas, modeling both parasitic inductances and capacitances, are within 3% of HSPICE simulation results.

This paper describes a fast method to estimate crosstalk noise in the presence of multiple aggressor nets for use in physical design automation tools. Since noise estimation is often part of the inner-loop of optimization algorithms, very efficient closed-form solutions are needed. Previous approaches have typically used simple lumped 3-4 node circuit templates. One aggressor net is modeled at a time assuming that the coupling capacitances to all quiet aggressor nets are grounded. They also model the load from interconnect branches as a lumped capacitor and use a dominant pole approximation to solve the template circuit. While these approximations allow for very fast analysis, they result in significant underestimation of the noise. In this paper, we propose a new and more comprehensive fast noise estimation model. We use a 6 node template circuit and propose a novel reduction technique for modeling quiet aggressor nets based on the concept of coupling point admittance. We also propose a reduction method to replace tree branches with effective capacitors which models the effect of resistive shielding. Finally, we propose a new double pole approach to solve the template circuit. We tested the proposed method on noise-prone interconnects from an industrial high performance processor. Our results show a worst-case error of 7.8% and an average error of 2.7%, while allowing for very fast analysis.