PASADENA, Calif., March 13, 2013 — Just as a Christmas tree’s lights go out when a single bulb dies, so, too, do electronic chips fail to work when a component stops functioning. A new self-healing integrated chip, however, could change all that, recovering from problems ranging from less-than-ideal battery power to total transistor failure in microseconds.
Engineers at California Institute of Technology have demonstrated this self-healing capability in tiny power amplifiers. The researchers destroyed various parts of the amplifiers’ chips by zapping them multiple times with a high-power laser, then observed as the chips automatically developed a work-around in less than 1 s.
“It was incredible the first time the system kicked in and healed itself. It felt like we were witnessing the next step in the evolution of integrated circuits,” said Ali Hajimiri, the Thomas G. Myers Professor of Electrical Engineering at Caltech. “We had literally just blasted half the amplifier and vaporized many of its components, such as transistors, and it was able to recover to nearly its ideal performance.”
Some of the damage Caltech engineers intentionally inflicted on their self-healing power amplifier using a high-power laser. The chip was able to recover from complete transistor destruction. This image was captured with a scanning electron microscope. Courtesy of Jeff Chang and Kaushik Dasgupta/Caltech.
Until now, even a single fault would render an integrated circuit chip completely useless. The engineers, members of the High-Speed Integrated Circuits laboratory in Caltech’s Division of Engineering and Applied Science, wanted to give integrated circuit chips a healing ability akin to that of our own immune system — something capable of detecting and quickly responding to a number of possible assaults to keep the larger system working optimally.
The devised power amplifier employs many robust on-chip sensors that monitor temperature, current, voltage and power. The information from the sensors feeds into a custom-made application-specific integrated circuit (ASIC) unit on the same chip, a central processor that acts as the system’s “brain.” The brain analyzes the amplifier’s overall performance and determines if it needs to adjust any of the system’s actuators.
The chip’s brain does not operate based on algorithms, but rather draws conclusions based on the aggregate response of the sensors.
“You tell the chip the results you want and let it figure out how to produce those results,” said Steven Bowers, a graduate student in Hajimiri's lab and lead author of the new paper. “The challenge is that there are more than 100,000 transistors on each chip. We don't know all of the different things that might go wrong, and we don't need to. We have designed the system in a general enough way that it finds the optimum state for all of the actuators in any situation without external intervention.”
Looking at 20 different chips, the investigators discovered that the amplifiers with the self-healing capability consumed about half as much power as those without, and their overall performance was much more predictable and reproducible.
“We have shown that self-healing addresses four very different classes of problems,” said Kaushik Dasgupta, another graduate student working on the project. The classes of problems include static variation that is a product of variation across components; long-term aging problems that arise gradually as repeated use changes the internal properties of the system; and short-term variations that are induced by environmental conditions such as changes in load, temperature and differences in the supply voltage; and, finally, accidental or deliberate catastrophic destruction of parts of the circuits.
The self-healing capability was first demonstrated in a power amplifier for millimeter-wave frequencies. Such high-frequency integrated chips are at the cutting edge of research and are useful for next-generation communications, imaging, sensing and radar applications. By showing that the self-healing technique works well in such an advanced system, the researchers hope to show that the approach can be extended to virtually any other electronic system.
“Bringing this type of electronic immune system to integrated circuit chips opens up a world of possibilities,” Hajimiri said. “It is truly a shift in the way we view circuits and their ability to operate independently. They can now both diagnose and fix their own problems without any human intervention, moving one step closer to indestructible circuits.”
The results appeared in IEEE Transactions on Microwave Theory and Techniques
For more information, visit: www.caltech.edu