In low power SoC for portable applications 0.5V operation will be required around '2010 to keep the total chip power fixed to 100mW with scaling [1]. Suppression of transistor static leakage current to 100pA/µm is also required to keep the static power level below 10% of the total power. One of the significant issues for these requirements is the severe degradation of the operation speed. Another key issue is the great influence of voltage fluctuation on the operation speed. To solve these issues, Bulk Dynamic threshold MOSFETs (B-DTMOS) and a Self-Adaptive Power supply System (SAPS) are investigated. Figure 22.9.1 shows the schematic cross section and the Ids-Vgs characteristics of the B-DTMOS compared to conventional MOS (Conv.MOS) with substrate voltages of 0V and 0.5V. The use of a Low Capacitance Sidewall Elevated Drain (LCSED) structure enabled a 60% reduction in both the occupation area of the serially connected transistor and the junction capacitance [3]. The main features of B-DTMOS characteristics are that the drive current is more than three times greater than Conv.MOS at 0V and that the leakage current is about two orders of magnitude smaller than Conv.MOS at 0.5V. A problem of high static leakage current due to the parasitic vertical bipolar transistor was suppressed by limiting the supply voltage to 0.5V.A gate array (GA) cell library containing 55 GA cells using B-DTMOS for the design of LSIs using 0.25µm design rules is developed. A Fully Static True Single Phase Clock (FS-TSPC) F/F circuit is designed and shown in Fig.22.9.2. The power dissipation of the four-stage toggle counter using 0.5V B-DTMOS with FS-TSPC F/Fs is decreased to 1/28 of that of the Conv.MOS operating at 2.5V. A CDMA MF LSI containing 130k gates is designed with a top down design methodology using the cell library. The cell area normalized to a standard CMOS cell area is also shown in Fig.22.9.2. Using the local interconnect ability of the LCSED structure to the fullest, a cell area almost equal to, or in some cases smaller than, that of the standard CMOS is achieved. Figure 22.9.3 shows speculated trend of B-DTMOS on chip clock frequency compared to that of High Performance (HP) logic [1]and Low Operation Power (LOP) Conv.MOS with 100pA/µm leakage current. Speculation is done by device simulation. The predicted speed of B-DTMOS is about 1/10 of that of HP throughout the generations. In the year 2010 almost same speed and about 1/2 the power dissipation will be realized by B-DTMOS compared to that of the Conv.MOS. After 2013 both speed and power dissipation of B-DTMOS will be superior to that of the Conv.MOS. Figure 22.9.4 shows the measured dependence of "Best case", "Typical" and "Worst case" inverter delay time on power supply voltage for the Conv.MOS, B-DTMOS and B-DTMOS with adaptive voltage control. 50mV variation of threshold voltage and supply voltage and from -40 to 85 O C temperature range were assumed. For the Conv.MOS the ratio of the "Best case" to the "Worst case" delay was about 50. It is, therefore, almost impos...
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An attractive product successfully attracts people when it is first introduced. More importantly, it maintains people’s interest throughout its lifetime. A product’s ability to maintain attractiveness is an important factor in the design of a long-life product. Yet, what specific product qualities provide this aspect of attractiveness and what specific design attributes affect quality. People perceive product quality by the use of different sensory modalities such as vision and touch. The dominance of a particular sensory modality and perception of product quality may change over time during product use. Two aspects are involved in this type of time-series change: (1) physical changes in the product (e.g. deterioration) and (2) users’ psychological changes during their experiences with a product. In this paper, we propose an experimental methodology that can be used to quantify the effects of design characteristics in relation to certain sensory modalities on users’ appraisals of product quality and on the customers’ beliefs during continued product use. The methodology analyzes changes in effects with respect to design parameters in relation to certain sensory modalities and in relation to two aspects of change. We applied the methodology to the design of a face lotion container. Qualities perceived by both vision and touch exerted significant effects on participants’ decisions to purchase a product and continue its use. We asked 30 female participants aged between twenty and thirty years to use a sample daily for one month. Participants were required to record their opinions of the samples (online assessment). On the first day, one week, and one month later, we invited participants to visit the laboratory. During those visits, they were asked to assess 24 samples that contained different visual designs, varied surface finishes, differing amounts of lotion, and different surface conditions (offline assessment). Based on these results, we demonstrated that the significance of design factors that participants perceived by different sensory modalities qualitatively and quantitatively changed over time. In this case study of lotion container design, we discovered that the potentially significant effect of a delicate surface finish that provided comfortable tactile sensations regardless of surface conditions on quality perception during long-term product use.
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