Sensor microchip uses 30,000-times less power than conventional chips

A low-power microchip 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 sets a low-power record and is intended for use in cutting-edge sensor-based devices such as medical implants, environment monitors or surveillance equipment according to researchers at the University of Michigan who developed the chip. 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.

Phoenix measures one square millimeter, but is the same size as its thin-film battery. “Low power consumption lets us 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,” said David Blaauw, a professor in the Department of Electrical Engineering and Computer Science “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% of their time. A low-power timer acts as an alarm clock on perpetual snooze, waking Phoenix every ten minutes for 1/10th of a second to run a set of 2,000 instructions. The list includes checking the sensor for new data, processing it, compressing it into a sort of short-hand, and storing it before going back to sleep, researchers said.

A unique power gate design is an important part of the sleep strategy. Power gates block the electric current from parts of a chip not essential for memory during sleep.In typical state-of-the-art chips, power gates are wide with low resistance to let through as much electric current as possible when the device is turned on. These chips wake up quickly and run fast, but leak electric current in sleep mode, researchers said.

Phoenix engineers used much narrower power gates that restrict the flow of electric current. That strategy, coupled with the deliberate use of an older process technology, cut down on energy leaks.To address this performance loss, the Michigan team increased the chip’s operating voltage, increasing the baseline power by approximately 20% when the chip is awake. But Phoenix still runs at 0.5 Volts, rather than the 1 to 1.2 Volts typical chips require.

The researchers are putting the Phoenix in a biomedical sensor to monitor eye pressure in glaucoma patients. Engineers envision that chips like this could also be sprinkled around to make a nearly invisible sensor network to monitor air or water or detect movement. They could be mixed into concrete to sense the structural integrity of new buildings and bridges.

Such low power chips are not of the same ilk being developed by Intel with its Atom family. The Atom family of low-power chips are destined for a new class of mini-laptops like the Asus Eee PC, as well as even smaller Internet devices. They compete with chips from Broadcom, Via Technologies, Arm and others.

In February, IBM said it had developed a prototype chip that could transmit up to 8 terabit/sec of information -- equivalent to about 5,000 high-definition video streams -- using the power of a single 100-watt light bulb.  

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