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Updated 11:00 AM June 30, 2008




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Low-power microchip sets record with sleep mode

A low-power microchip developed at U-M uses 30,000 times less power in sleep mode and 10 times less in active mode than comparable chips now on the market.

The Phoenix Processor, which sets a low-power record, is intended for use in cutting-edge sensor-based devices such as medical implants, environment monitors or surveillance equipment.

The chip consumes 30 picowatts during sleep mode. A picowatt is one-trillionth of a watt. Theoretically, the energy stored in a watch battery would be enough to run the Phoenix for 263 years.

Scott Hanson, a doctoral student in the Department of Electrical Engineering and Computer Science, was to present the design June 20 at the Institute of Electrical and Electronics Engineers' Symposium on VLSI Circuits. Hanson jointly leads this project with Mingoo Seok, a doctoral student in the same department.

Phoenix measures one square millimeter. There's nothing special about its size, as chips in many modern sensors and electronics are one square millimeter and smaller. But Phoenix is the same size as its thin-film battery, marking a major achievement.

In most cases, batteries are much larger than the processors they power, drastically expanding the size and cost of the entire system, says David Blaauw, a professor in the Department of Electrical Engineering and Computer Science. For instance, the battery in a laptop computer is about 5,000 times larger than the processor and it provides only a few hours of power.

"Low power consumption allows us to reduce battery size and thereby overall system size. Our system, including the battery, is projected to be 1,000 times smaller than the smallest known sensing system today," Blaauw says. "It could allow for a host of new sensor applications."

To achieve such low power, Phoenix engineers focused on sleep mode, where sensors can spend more than 99 percent of their lives. Sensors wake only briefly to compute at regular intervals.

"Sleep mode power dominates in sensors, so we designed this device from the ground up with an efficient sleep mode as the No. 1 goal. That's not been done before," says Dennis Sylvester, an associate professor in the Department of Electrical Engineering and Computer Science.

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