MIT: Human body heat may someday power energy-efficient chip

Computerworld - A new energy-efficient chip designed by researchers at MIT may one day be able to run implantable medical devices using human body heat as an energy source.

The new chip design, which researchers say will consume 10 times less power than traditional chips, is being unveiled today at the International Solid State Circuits Conference in San Francisco. The chip, still in the proof-of-concept stage, is expected to be used in portable electronic devices like cell phones and PDAs, and even in implantable medical systems.

"We intend to implant these new low-voltage techniques as quickly as we can," said Dennis Buss, chief scientist at Texas Instruments Inc. TI engineers worked with MIT researchers on the two-year project. "To get to where we'd need to be with this will take about five years," said Buss. "Doing a research demonstration is an important step, but making it robust for commercial production will require some work."

The key to the chip's improved energy efficiency lies in making it work at a reduced voltage level, according to Joyce Kwong, a graduate student in MIT's Department of Electrical Engineering and Computer Science and a member of the chip design project team. Most of today's mobile processors operate at about 1 volt. The requirement for MIT's new design, however, is 0.3 volts.

When you use the standard equation to calculate how much power a chip will use, the voltage is squared. That means if voltage is increased, power consumption will jump. However, if voltage is decreased, power consumption will plummet.

"Voltage is critical," said Jim McGregor, an analyst at In-Stat. "All these handheld devices are being asked to do more and more. To be able to decrease voltage lets you increase silicon complexity to handle more functions, and it also increases battery life, which is a critical component in multiple applications."

However, the voltage required by a cell phone or handheld device depends on what the device is doing. Buss explained that if the chip is idle, 0.3 volts would be enough to operate the chip. However, if the device is doing something that requires high speed, the chip would need to use more voltage. And the chip is designed to scale between higher and lower voltages.

"The concept we have calls for dynamic voltage scaling," added Buss. "The voltage can be increased or decreased depending on how much computation you have to do. When you need to go fast, you turn up the voltage. When you have a sleep mode or standby, then you can drop the voltage and save substantial power."

Buss explained that the chip uses DC-to-DC converters, which control the voltage levels. Multiple converters, he added, can set different levels depending on a device's function at a specific moment. Moving to low-voltage levels whenever possible would save energy consumption.