Researchers at the Massachusetts Institute of Technology (MIT) and Texas Instruments have developed a topology that shows promise for ultra-low-power systems with a chip design that can be up to 10 times more energy-efficient than present technology. The design could lead to cell phones, implantable medical devices, and sensors that last far longer when running from a battery.
So far, the novel chip is a proof of concept. Commercial applications could become available “in five years, maybe even sooner, in a number of exciting areas,” says MIT professor Anantha Chandrakasan. For example, portable and implantable medical devices, portable communications devices, and networking devices could be based on such chips, which would greatly increase their operating times. There may also be a variety of military applications in the production of tiny, self-contained sensor networks that could be dispersed in a battlefield.
Working with Chandrakasan were graduate students, Joyce Kwong, Yogesh Ramadass and Naveen Verma. Their Texas Instruments (TI) collaborators were Markus Koesler, Korbinian Huber, and Hans Moormann. The team demonstrated the ultra-low-power design techniques on TI’s MSP430, a widely used microcontroller. The work was conducted at the MIT Microsystems Technology Laboratories directed by Chandrakasan.
The key to the improved energy efficiency was to find ways of making the circuits on the chip work at a voltage level much lower than usual, notes Chandrakasan. While most current chips operate around 1 V, the new design works at just 0.3 V.
Reducing the operating voltage, however, isn’t as simple as it might sound, because existing microchips have been optimized for many years to operate at the higher standard-voltage level. “Memory and logic circuits have to be redesigned to operate at very low power-supply voltages,” says Chandrakasan.
One key to the new design, he says, was to build a high-efficiency dc-dc converter that reduces the voltage to the lower level right on the same chip, reducing the number of separate components. The redesigned memory and logic, along with the dc-dc converter, are all integrated to realize a complete system-on-a-chip solution.
One of the biggest problems the team had to overcome was the variability that occurs in typical chip manufacturing. At lower voltage levels, variations and imperfections in the silicon chip become more problematic. “Designing the chip to minimize its vulnerability to such variations is a big part of our strategy,” says Chandrakasan.
In some applications, such as implantable medical devices, the goal is to make the power requirements so low that they could be powered by “ambient energy,” says Chandrakasan. In other words, they would use the body’s own heat or movement to provide all the needed power. In addition, the technology could be suitable for body-area networks or wirelessly enabled body sensor networks. The research was funded in part by a grant from the U.S. Defense Advanced Research Projects Agency.
Massachusetts Institute of Technology