The efficient control, storage, and distribution of energy are worldwide challenges, and are increasingly important areas of analog circuit research. While the manipulation and storage of information is efficiently performed digitally, the conversion and storage of energy must fundamentally be performed with analog systems. As a result, the key technologies for power management are predominantly analog. For example, there is much interest in wireless power transmission for battery charging applications, ranging from mobile handsets to medical implants, and increased efficiency in wireless power transmission is enabling faster charging over longer distances. There is also an explosion of technologies that permit energy to be collected from the environment via photovoltaic, piezoelectric, or thermoelectric transducers. A significant focus here is on analog circuits that are able to harvest sub-microwatt power levels from energy sources at 10’s of millivolts, to provide autonomy for remote sensors or to supplement conventional battery supplies in mobile devices. To achieve this, extremely low power must be consumed by the attendant analog circuits so that some energy is left over to charge a battery or super capacitor. Similarly, the power consumption of analog instrumentation amplifiers, oscillators, and audio power amplifiers is being scaled down to meet the demands of these low power systems. Fast power-up and -down is also desired from these circuits to permit high energy-efficiency during intermittent operation. Together, these technologies will permit devices to be powered indefinitely from sustainable sources, opening the door to ubiquitous sensing, environmental monitoring, and medical applications.
Analog circuits also serve as bridges between the digital world and the analog real world. Just like the bridges in our roads, analog circuits are often bottlenecks and their design is critical to overall performance, efficiency, and robustness. Nevertheless, digital circuits such as microprocessors drive the market; so semiconductor technology has been optimized relentlessly over the last 40 years to reduce the size, cost, and power consumption of digital circuits. Analog circuitry has proven increasingly difficult to implement using these modern IC technologies. For example, as the size of transistors has decreased, the range of analog voltages they can handle has decreased and the variation observed in their analog performance has increased.
These aspects of semiconductor technology explain two key divergent trends in analog circuits. One trend is to forgo the latest digital IC manufacturing technologies, instead fabricating analog circuits in older technologies, which may be augmented to accommodate the high voltages demanded by increasing markets in medical, automotive, industrial and high-efficiency lighting applications. Other applications dictate full integration of analog and digital circuits together in our most modern digital semiconductor technologies. For example, microprocessors with multiple cores can reduce their overall power consumption by dynamically scaling operating voltage and frequency in response to time-varying computational demands. For this purpose, DC-DC voltage converters can be embedded alongside the digital circuitry, driving research into the delivery of locally regulated power supplies with high efficiency and low die area, but without recourse to external components.
This and other related topics will be discussed at length at ISSCC 2013, the foremost global forum for new developments in the integrated-circuit industry. ISSCC, the International Solid State Circuits Conference, will be held on February 17-21, 2013, at the San Francisco Marriott Marquis Hotel.