The design cycle

The traditional way to design electronic circuits is as follows firstly specification of the behaviour of the systems secondly simulation of the behaviour diirdly transformation of this behavioural description into a dataflow fourthly structural description, verifying along the way that each decomposition stage maintains the exact behaviour as detailed in the behavioural specification. The final stage is then to transfer the structural description 

Figuie 2.2 Design process with VHDL logic synthesis software. 

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Since reliability and the related measures are essentially design parameters, improvements are most easily and economically accomplished early in the design cycle. Useful techniques for design reUabiUty improvement are described below. 

Failure Mode and Effects Analysis. The system design activity usually emphasizes the attainment of performance objectives in a timely and cost-efficient fashion. The failure mode and effects analysis (FMEA) procedure considers the system from a failure point of view to determine how the product might fail. The terms design failure mode and effects analysis (DFMEA) and failure mode effects and criticaUty analysis (EMECA) also are used. This EMEA technique is used to identify and eliminate potential failure modes early in the design cycle, and its success is well documented (3,4). 

Each topology has predictable voltage and current stresses for the power switches and rectifiers. These estimates have about a 90 percent confidence factor. Selecting the power devices at this stage in the design cycle can save precious time later in the program by not having to wait for parts. Table 3-2 contains equations that may be conservative in nature, but will work in the application. 

Preliminary consideration of candidate materials, processes and tooling factors, configuration, thicknesses in section, ribs, bosses, holes, surface characteristics, color, graphics, decoration, and assembly methods will begin to impose some discipline on the product design as it evolves. In the middle and latter phases of the design cycle, two or three concepts should make their validity apparent to all involved. With luck (logic), one will... 

Effective structure-activity relationship (SAR) generation is at the centre of any medicinal chemistry campaign. Much work has been done to devise effective methods to explain and explore SAR data for medicinal chemistry teams to drive the design cycles within drug discovery projects (1). Recent work on SAR generation highlights the commonly observed discontinuity of SAR and bioactivity data, the so-called activity cliffs (2). This also emphasises the need to empirically determine SAR for each lead... 

FIGURE 9.2 Computer-aided design, in this case of fuel additives, makes the design cycle much shorter and more efficient by more narrowly directing the molecular search. 

Design Scorecards have many uses, but primarily they identify which parameters or indicators contribute most to an optimized design. This helps your innovation team decide where to focus efforts early in the design cycle. 

First, the cvcle is broken down into its component activities. Table I represents a reaction consisting of a sequence of seven steps. Fhe allotted time is the design cycle time, budgeted cycle time or a judgmental optimum time for each activity it is the standard against which actual performance will be compared. 

To ensure most economically and effectively the production of a reliable product, the reliability activities must start early in the product-development cycle. However, at this stage, the identification of reUahility improvements depends heavily on the experience of the personnel studying the product from blueprints and preliminary system mock-ups because no hard data are available for a quantitative assessment of reliability. To consider reliability early in the design cycle, one must rely on a formalized design review procedure, which is now briefly explained. 

A complete design review procedure must be multiphased in order to follow the design cycle until the system is released for production. A typical example of a review committee, including personnel and their responsibilities, is shown in Table 1. Here the review process has been subdivided into three phases, and each phase is an update of more detailed analysis based on the latest knowledge. 

In the next subsection, attention is focused on a technique that has been proven effective in identifying failure situations early in the design cycle and before product testing. 

After all, not all the factors can be identified in the design cycle, so summative evaluation is needed, which is a basis for actual result and for warning improvement. Summative evaluation can be the sole approach to evaluation, or it can be combined with formative evaluation. In summative evaluation, the final product (warning sign) must be released into the context of use, and then criterion measures can be gathered from participants over a period of time. 

G4 Introduce the design cycle Limit criticism that gains are due to use of easier conceptual questions Increases traditional problem-solving skill... 

McMillan, K. L. (1994), Fitting formal methods into the design cycle, in Proc. DAC 94 , San Diego, pp. 314-319. 

This curve is termed Pareto curve cf. explanatory note 8.1) and clearly shows that one objective function can only be improved at the expense of the other objective function. This trade-off leads to significant deviations between optimal designs and the utopia point (up to 60%) for the pair /4on /exergy The decision maker should have in mind the importance of compromising both objectives at early stages of the design cycle. 

This approach demands reassessment of the design requirements for particular projects. Particularly useful in project-based industries, the aim is to focus on manufacturing issues at an early stage in the design cycle. 

The last step in the design cycle is the end-use testing, or field trials. This can be done using selected individuals or applications which are closely monitored or controlled. This information will indicate whether or not the part performed as the designer antici-... 

The 2002 National Electronics Manufacturing Initiative (NEMI) roadmap cited design infrastructure — education, tools, and standard practices — as a major gap that hinders broad adoption of LTCC in volume applications. Mthout this necessary design infrastructure, the design cycle relies on multiple design-build-test iterations, a highly inefficient process. 

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