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Worst-case circuit analysis (WCCA or WCA) is a cost-effective means of screening a design to ensure with a high degree of confidence that potential defects and deficiencies are identified and eliminated prior to and during test, production, and delivery. It is a quantitative assessment of the equipment performance, accounting for manufacturing, environmental and aging effects. In addition to a circuit analysis, a WCCA often includes stress and derating analysis, failure modes and effects criticality (FMECA) and reliability prediction (MTBF). The specific objective is to verify that the design is robust enough to provide operation which meets the system performance specification over design life under worst-case conditions and tolerances (initial, aging, radiation, temperature, etc.). Stress and de rating analysis is intended to increase reliability by providing sufficient margin compared to the allowable stress limits. This reduces overstress conditions that may induce failure, and reduces the rate of stress-induced parameter change over life. It determines the maximum applied stress to each component in the system. == General information == A worst-case circuit analysis should be performed on all circuitry that is safety and financially critical. Worst-case circuit analysis is an analysis technique which, by accounting for component variability, determines the circuit performance under a worst-case scenario (under extreme environmental or operating conditions). Based on the worst-case and the Worst-Case Distance with respect to variability expected yield can be calculated.〔http://mediatum.ub.tum.de/doc/1086708/1086708.pdf〕 Environmental conditions are defined as external stresses applied to each circuit component. It includes temperature, humidity or radiation. Operating conditions include external electrical inputs. Component quality level, interaction between parts, and drift due to component aging. WCCA helps in the process of design reliability into hardware for long-term field operation. Electronic piece-parts fail in two distinct modes: Out-of-tolerance limits: Through this, the circuit continues to operate, though with degraded performance, and ultimately exceeds the circuit's required operating limits. Catastrophic failures may be minimized through MTBF, stress and derating, and FMECA analyses that help to ensure that all components are properly derated, as well as that degradation is occurring “gracefully...” A WCCA permits you to predict and judge the circuit performance limits beneath all of the combos of half tolerances. There are many reasons to perform WCCA. Here are a few that may be impactful to schedule and cost. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Worst-case circuit analysis」の詳細全文を読む スポンサード リンク
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