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The term mixed-signal is fairly commonplace when talking about integrated circuits. Mixed-signal has been the most common application of digital and analog residing in a monolithic integrated circuit (IC). Simply stated, mixed-signal is usually a “kitchen-sink” analog IC which was the only place to shove some more digital. Maybe this is an analog guy’s opinion -- it could also be a digital chip with some analog shoved into it. In some cases, the two technologies do interact to improve system performance, but seldom if ever is this optimal. However, the combination of digital and analog has paved the way to solving one of the most challenging issues that system designers face -- power consumption.
In the world today, energy conservation is a challenge which all of us must understand and consider. We applaud Energy Star as a noble effort to improve the power consumption of electronic products, we appreciate the benefits of long-lasting batteries in our portable devices, and we’re aware that the power consumption of datacom infrastructure and terabyte hard drive farms is eating into corporate profits.
Why then, when we know how important it is to conserve energy, do we see design engineers opting so often for the cheaper power supply design instead of the more efficient alternative? The easy answer is that electronic designs are a lot more complex these days, requiring more voltages, and the cost of power supplies has risen to the point that engineers are almost forced to go for price over performance.
It is important that design engineers consider the total cost of power. For example, by using high-efficiency conversion, could the upstream power source be down-sized and cost reduced? Could your product be marketed as lower-power and get a price premium?
For most step-down conversion applications, designers should use power-efficient DC-DC switching regulators if the output voltage they require is less than 70 percent of the input voltage source and the device being powered consumes more than 10 percent of total “average” power. If Vin/Vout is greater than 70 percent, the benefit of using a DC-DC regulator instead of a linear regulator is not worth the extra cost unless the dissipated power exceeds the capabilities of the package.
Semiconductor companies now acknowledge that power management optimization begins when digital ICs are being designed. Not so long ago, power management amounted to voltage regulators sprinkled around a circuit board, packed into a remote corner or, best case, integrated into a mixed-signal chip.
Figure 1. As features are added to electronics, crowding results with the sprinkling of voltage regulators
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