An energy-efficient microchip

A cell phone dying at a crucial moment, a digital camera that warns of low power at a perfect photo opportunity or a laptop inopportunely running out of juice — many of us have had such vexing experiences firsthand.

Researchers at the Massachusetts Institute of Technology and Texas Instruments (TI) have designed a chip, ten times more energy-efficient than existing ones, to keep portable devices going longer.

Because of the lower power consumption, the batteries of these mobile devices and vital medical implants do not have to be recharged or replaced as frequently as they are now.

Although users tend to be excited by new features on gadgets, every additional feature — like the ability to watch video clips or take snapshots on a cell phone — puts a burden on the battery’s limited power.

Clearly, a new approach to chip design was in order because saddling such portable devices with bigger and better batteries can only take us so far. In such devices, the key to turn down power consumption was the voltage, says Prof. Anantha Chandrakasan, Director of MIT’s Microsystems Technology Laboratories .

The longevity of the battery comes from the chip’s lower voltage requirement.

The operating voltage for circuits on a chip is typically 1 volt but the new chip can operate at just 0.3 volts. An important feature of this new chip’s design is a high-efficiency DC-to-DC converter — akin to an in-situ step-down transformer — that slashes the input voltage to one third of its strength.

Traditionally, the circuits on such chips have been optimised to operate at a supply voltage of around 1 volt. Scaling down the supply voltage has huge implications.

Memory and logic circuits had to be redesigned to operate at 0.3 volts, a voltage low enough to disrupt the chip’s very functionality, says Chandrakasan, the leader of the chip’s re-architecture team.

Besides, the team also had to overcome the variability inherent in chip manufacturing. At this lower supply voltage, variations and imperfections in the silicon chip could throw the electronic circuit out of whack; in the binary system what was registered as 1 could become 0 and vice versa. Designing the chip to minimize its vulnerability at the new voltage was a huge challenge.

“These design techniques show great potential for TI’s future low-power integrated circuit products and applications including wireless terminals, battery-operated instrumentation, sensor networks and medical electronics,” says Dr. Dennis Buss, chief scientist at Texas Instruments.

Networking devices

Portable and embedded medical devices, such as hearing aids and retinal implants, communications and networking devices based on such chips will consume only a tenth of the current power.

A person who now watches short clips on a cell phone, for instance, can view longer videos without the need to recharge. There could also be a variety of military applications in the production of tiny, self-contained sensor networks that could be dispersed in a battlefield.

Eventually, in medical devices the idea is to make the power requirement so low that they could run on ‘ambient energy’ — using the body’s own heat or movement to provide the requisite power.

The ultimate goal is to design a generator on a chip, eliminating the need for a battery, says Chandrakasan.