TECHNOLOGY FOR CHANGE

Smarter Microchips Heal Themselves

R. Colin Johnson | Date: 10-15-09 | Comments

DARPA teams with Raytheon to craft microchips that sense their own malfunctions and automatically heal themselves.

"Circuit, heal thyself" is the motto of the Self-HEALing mixed-signal Integrated Circuits (HEALICs) program at the Defense Advanced Research Project Agency. DARPA recently granted defense contractor Raytheon a phase one $5.5 million award to design, fabricate and test self-healing circuits. Raytheon is crafting smarter radio-frequency (RF) and mixed-signal (analog+digital) microchips that sense their own malfunctions and automatically heal themselves.

Raytheon is partnering with both the California Institute of Technology and North Carolina State University on the contract, which will be worth $11 million total if phase two is subsequently awarded too.

Most microchip research efforts are aimed at making better, more perfect devices. The HEALICs program, on the other hand, aims to add smarter circuitry that compensates for when chips are not perfect, thereby healing them. The problem today is that because microchips have been scaled down to the nanoscale, process variations have become an unavoidable fact of life. Now that electronic films are only a few nanometers thick, variations of just a few atoms can change the response of circuitry, as can wide temperature swings and just getting old.

Digital circuitry has a kind of built-in compensation, since it recognizes only ones and zeros, which can be off slightly with no harm done. Analog and RF circuitry, on the other hand, depends on smooth, accurate responses. To self-heal mixed-signal circuitry that contains both analog and digital circuitry, Raytheon uses sensors to detect a sub-circuit's output, compare it to stored values of what it's supposed to be, then recalibrate the circuit to restore correct operation. Adding such self-calibration circuitry also allows chips to compensate for harsh environmental conditions and even the effects of long-term aging.

"We are determining new general algorithmic approaches to support the implementation of self-calibrating circuits," said Professor Paul Franzon at North Carolina State University about his work with Raytheon. "We are working on general approaches to designing the calibration sub-circuits that will improve their efficiency and implementation cost."

Efficient implementations that add very little extra cost is one of DARPA's stated goals for self-healing circuits, as well as adding no more than 10 percent to the power consumed by a chip in phase one, and no more than 5 percent in phase two. Phase one will result in a mixed-signal core with about 1,000 transistors that performs the application's key function. Phase two will surround that core with a million-transistor system-on-chip that implements the complete application.

Raytheon claims its solution to self-healing circuits works across an entire system-on-chip, regardless of the device types used there, unlike rival approaches that use device-specific tuning techniques. Eventually, the HEALICs program will result in a set of auto-calibrating core libraries that can be used by designers over a wide range of self-healing mixed-signal applications.