This paper proposes a cell layout synthesis technique to minimize the sensitivity to wiring faults due to spot defects. We modeled the sensitivity to faults on intra-cell routings with consideration to the spot defects size distribution and the end effect of critical areas. The effect of the sensitivity reduction on the yield is also discussed. By using the model as a cost function, we comprehensively generate the minimum width layout of CMOS logic cells and select the optimal layouts. Experimental results show that our technique reduces about 15% of the fault sensitivities compared with the wire-length-minimum layouts for benchmark CMOS logic circuits which have up to 14 transistors.

In modern CMOS digital design, the noise immunity has come to have an almost equal importance to the power consumption. In the last decade, many low power design schemes have been presented. However, no one can simply judge which one is the best from the noise immunity point of view. In this paper, we investigate the noise immunity of the static CMOS low power design schemes in terms of logic and delay errors caused by different kinds of noise existing in the static CMOS digital circuits. To fulfill the aims of the paper, first a model representing the different sources of noise in deep submicron design is presented. Then the model is applied to the most famous low power design schemes to find out the most robust one with regard to noise. Our results show the advantages of the dual threshold voltage scheme over other schemes from the noise immunity point of view. Moreover, it indicates that noise should be carefully taken into account when designing low power circuits; otherwise circuit performance would be unexpected. The study is carried out on three circuits; each is designed in five different schemes. The analysis is done using HSPICE, assuming 0.18 µm CMOS technology.

This paper proposes flat and hierarchical approaches for generating a minimum-width transistor placement of CMOS cells in presence of non-dual P and N type transistors. Our approaches are the first exact method which can be applied to CMOS cells with any types of structure. Non-dual CMOS cells occupy a major part of an industrial standard-cell library. To generate the exact minimum-width transistor placement of non-dual CMOS cells, we formulate the transistor placement problem into Boolean Satisfiability (SAT) problem considering the P and N type transistors individually. Using the proposed method, the transistor placement problem of any types of CMOS cells can be solved exactly. In addition, the experimental results show that our flat approach generates smaller width placement for 29 out of 103 dual cells than that of the conventional method. Our hierarchical approach reduces the runtimes drastically. Although this approach has possibility to generate wider placements than that of the flat approach, the experimental results show that the width of only 3 out of 147 cells solved by our hierarchical approach are larger than that of the flat approach.

This paper compares a stub and a decoupling capacitor for power supply noise reduction. A quarter-length stub attached to the power supply line of an LSI chip works as a band-eliminate filter, and suppresses the power supply bounce of the designed frequency. The conditions where the stub is more effective than the same-area decoupling capacitor are clarified. The stub will work more efficiently and on-chip integration will be possible on high frequency operation LSIs.

In this paper we show that self synchronous circuits can provide robust operation in both soft error prone and low voltage operating environments. Self synchronous circuits are shown to be self checking, where a soft error will either cause a detectable error or halt operation of the circuit. A watchdog circuit is proposed to autonomously detect dual-rail '11' errors and prevent propagation, with measurements in 65 nm CMOS showing seamless operation from 1.6 V to 0.37 V. Compared to a system without the watchdog circuit size and energy-per-operation is increased 6.9% and 16% respectively, while error tolerance to noise is improved 83% and 40% at 1.2 V and 0.4 V respectively. A circuit that uses the dual-pipeline circuit style as redundancy against permanent faults is also presented and 40 nm CMOS measurement results shows correct operation with throughput of 1.2 GHz and 810 MHz at 1.1 V before and after disabling a faulty pipeline stage respectively.

This paper demonstrates an on-chip di/dt detector circuit. The di/dt detector circuit consists of a power supply line, an underlying spiral inductor and an amplifier. The mutual inductor induces a di/dt proportional voltage, and the amplifier amplifies and outputs the value. The measurement results show that the di/dt detector output and the voltage difference between a resistor have good agreement. The di/dt reduction by a decoupling capacitor is also measured using the di/dt detector.

We propose a high-sensitivity and wide-dynamic-range position sensor using logarithmic-response and correlation circuit. The 3-D measurement system using the proposed position sensor has advantages to applications, for example a walking robot and a recognition system on vehicles, which require both of availability in various backgrounds and safe light projection for human eyes. The position sensor with a 64 64 pixel array has been developed and successfully tested. We describe the sensitivity of position detection as SBR (Signal-to-Background Ratio). The minimum SBR of the sensor is -13.9 dB lower than standard sensors. High sensitivity under -10 dB SBR is realized in a dynamic range of 41.7 dB in terms of background illumination. Experimental results of position detection and 3-D measurement in a strong background illumination are also presented.

Dynamic performance of ultra-thin SIMOX (Separation by IMplanted OXgen) CMOS circuits has been studied using ring oscillators. A novel concept of current-delay product, along with an equivalent linear resistance of MOSFETs, is applied for deriving effective load capacitance of near 0.1 µm gate CMOS circuits. Calculation results showed quatitative agreement with measurement data. It was found that the gate-fringing capacitance limits the delay time is the case of under 0.2 µm gate-length. The lower bound of power-delay product of SIMOX/SOI is expected as low as 0.2 fJ for the gate length of 0.15 µm at the supply voltage of 1.5 V.

We have proposed a generic architecture that can integrate the aspects of confidentiality and integrity into the A/D conversion framework. A conceptual account of the development of the proposed architecture is presented. Using the principle of this architecture we have presented a CMOS circuit design to facilitate a fully integrated Authenticated-Encrypted ADC (AE-ADC). We have implemented and demonstrated a partial 8-bit ADC Analog Front End of this proposed circuit in 0.18µm CMOS with an ENOB of 7.64 bits.

In this paper, we present a hierarchical multi-chip architecture which employs fully digital and word-parallel associative memories based on Hamming distance. High capacity scalability is critically important for associative memories since the required database capacity depends on the various applications. A multi-chip structure is most efficient for the capacity scalability as well as the standard memories, however, it is difficult for the conventional nearest-match associative memories. The present digital implementation is capable of detecting all the template data in order of the exact Hamming distance. Therefore, a hierarchical multi-chip structure is simply realized by using extra register buffers and an inter-chip pipelined priority decision circuit hierarchically embedded in multiple chips. It achieves fully chip- and word-parallel Hamming distance search with no throughput decrease, additional clock latency of O(log P), and inter-chip wires of O(P) in a P-chip structure. The feasibility of the architecture and circuit implementation has been demonstrated by post-layout simulations. The performance has been also estimated based on measurement results of a single-chip implementation.

This paper prsesnts a reduced swing signal data transmission method for the bus architectures in VLSIs, which consists of small size bus drivers of inverters, dual rail transmission lines, termination resistors and sense amplifiers for regenerating signal swing. The optimum value of signal swing and driving capacity of sense amplifier are given as functions of transmission line capacitance based on a criterion of areadelay2 for guideline. Using results of analysis, we propose a self-controlled data transmission module for the optimum reduced swing signal. Applying the method to a 32bit bus architecture, it is shown that total area, cycle time and total power consumption are 66,070[µm2], 0.90[ns], 32.2[mW], respectively, while those are 284,000[µm2], 1.12[ns], 173.4[mW], respectively, in the conventional chained buffer module. The proposed method is less noisy than the conventional chained buffer method.

This paper demonstrates a power supply noise reduction using on-board stubs. A quarter-length stub attached to the power supply line of an LSI chip works as a band-eliminate filter, and suppresses the power supply noise of the designed frequency. Preliminary experiments show that 87% of the designed frequency noise component is suppressed when stub patterns are written on a power supply area on a PCB board for a 1.25 GHz operating LSI. The results show the possibility of the stub on-chip integration when the operating frequency of LSIs becomes higher and the stub length becomes shorter.

We propose a shot reduction technique of character projection (CP) Electron Beam Direct Writing (EBDW) using combined cell stencil (CCS) or the advanced process technology. CP EBDW is expected both to reduce mask costs and to realize quick turn around time. One of major issue of the conventional CP EBDW, however, is a throughput of lithography. The throughput is determined by numbers of shots, which are proportional to numbers of cell instances in LSIs. The conventional shot reduction techniques focus on optimization of cell stencil extraction, without any modifications on designed LSI mask patterns. The proposed technique employs the proposed combined cell stencil, with proposed modified design flow, for further shot reduction. We demonstrate 22.4% shot reduction within 4.3% area increase for a microprocessor and 28.6% shot reduction for IWLS benchmarks compared with the conventional technique.

This paper presents a structural approach for synthesizing arbitrary multi-output multi-stage static CMOS circuits at the transistor level, targeting the reduction of transistor counts. To make the problem tractable, the solution space is restricted to the circuit structures which can be obtained by performing algebraic transformations on an arbitrary prime-and-irredundant two-level circuit. The proposed algorithm is guaranteed to find the optimal solution within the solution space. The circuit structures are implicitly enumerated via structural transformations on a single graph structure, then a dynamic-programming based algorithm efficiently finds the minimum solution among them. Experimental results on a benchmark suite targeting standard cell implementations demonstrate the feasibility and effectiveness of the proposed approach. We also demonstrated the efficiency of the proposed algorithm by a numerical analysis on randomly-generated problems.

This paper demonstrates a feedforward active substrate noise cancelling technique using a power supply di/dt detector. Since the substrate is usually tied with the ground line with a low impedance, the substrate noise is closely related to the ground bounce which is proportional to the di/dt when inductance is dominant on the ground line impedance. Our active cancelling detects the di/dt of the power supply, and injects an anti-phase current into the substrate so that the di/dt-proportional substrate noise is cancelled out. Our first trial shows that 34% substrate noise reduction is achieved on our test circuit, and the theoretical analysis shows that the optimized canceller design will enhance the substrate noise suppression ratio up to 56%.

This paper describes the design and development of a module generator for a dual-rail PLA with embedded 2-input logic cells for 0.35 µm CMOS technology. In order to automatically generate logic-cell based PLA layouts from circuit specifications, a module generator as a design automation tool of logic-cell based PLA is developed with a structural improvement. This module generator is based on a timing-driven design methodology and consists of logic synthesis, transistor sizing and logic cell generation, stimulus generation, HDL model generation parts. This generator uses a design constraint to achieve a flexible transistor sizing in a logic cell generation part. In addition, generated logic cells can be easily adapted to a layout generator. The layout is generated by using 0.35 µm, 3-metal-layer CMOS technology. Moreover, an HDL model generator is developed to create delay behavior models easily and quickly with precise timing parameters. The design complexity which is becoming an important issue for VLSI circuits can be reduced partially and human caused errors are minimized by module generator. A PLA layout in GDS-II form and an HDL model behavior of a Boolean function which has 64-bit input, 1-bit output and 220 product term can be generated within 8 minutes on a SunUltraSPARC-III 900 MHz processor. A very short time is required to compile the module, and this makes it feasible for designers to try many different design configurations in order to get the better one.

This paper presents a decoupling capacitance boosting method for the resonant supply noise reduction by fast voltage hopping of DVS systems. The proposed method utilizes a foot transistor as a switch between a conventional decoupling capacitor (decap) and GND. The switching controls of the foot transistor depending on the supply noise states achieve an effective noise reduction as well as fast settling time compared with the conventional passive decaps. The measurement results of a test chip fabricated in a 0.18 µm CMOS technology show 12X boost of effective decap value, and 65.8% supply noise reduction with 96% settling time improvement.