Principles of Top-Down Mixed-Signal Design
entail some sacrifice in overall system performance, changing to a top-down design methodology does not inherently imply lower system performance. In fact, the opposite is usually the case, using top-down design results in higher performance. Rather, the sacrifice that is demanded of analog and mixed-signal designers is that they must learn new skills, such as behavioral modeling, and they must be more disciplined in the way they design.
It is unlikely that analog and mixed-signal designers will ever be allowed on a large scale to trade any substantial amount of performance and power for a reduction in design time. Rather, in those cases where the performance and power requirements are not demanding, a digital implementation is usually preferred.
2 Design Drivers
Design of mixed-signal systems is getting more and more challenging, which is increas- ing the pressure to fix the analog design productivity problem. The challenges come in five different forms: the need to complete designs more quickly, the need to take on larger more complex designs, the need to increase the predictability of the design pro- cess, the need to reuse existing designs in order to more quickly and cheaply develop new designs, and the increasingly fluid nature of design and process requirements.
Getting to Market First
With the internet and wireless technology as the latest market drivers, the pace of the electronic marketplace continues to quicken. New products and new product categories are being created faster than ever before. In order to keep up with the rapid pace of the market, designers must get their products to market faster than ever. Those that are suc- cessful at bringing significant new capabilities to the market first are usually rewarded with higher profit margins and greater market share. Conversely, those that are late must face an uphill battle against entrenched competition. In fact, in markets where the prod- uct lifetime is short, the three month delay associated with a respin can be the difference between taking the market, and having no market at all.
To understand this, consider three scenarios for developing a product with Figure 1 showing the expected revenue for each scenario. For the first, consider employing an efficient product development process and being first to market. For the second, con- sider using the same number of developers with an inefficient development process, thereby causing the product to be late to market. This results in a much lower return because the product enters a market where a competitor has already established leader- ship position and because there are fewer available customers left. Finally, consider using an inefficient development process but increasing the number of developers in order to reach the market first. If this were possible, the development costs are higher, but the total return is almost the same as in the first case. This is because the returns are expected to be much greater than the initial development costs.
This example illustrates why it is often more important to get a product to the market first than it is to control development costs. Of course this assumes that the product is the right product in that it satisfies the customers needs, and that it has some new and valuable capability. With follow on products, the situation is somewhat different. Here,
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