Magnetic Materials and Stacked-Chip Circuit Design for Integrated Power Converters Enable Energy Densities 10 Times Greater than Current Solutions
RESEARCH TRIANGLE PARK, N.C. — (BUSINESS WIRE) — February 22, 2012 — Semiconductor Research Corporation (SRC), the world's leading university-research consortium for semiconductors and related technologies, and Columbia University today announced research results that place industry focus back onto voltage regulators as a solution for continued processor scalability. Having just proven a new generation of integrated voltage regulator (IVR) that features energy densities more than ten times that of present state-of-art inductors available on computer chips, the team is preparing to test a second round of prototypes.
The research team is working to solve an industry predicament where the increasing use of parallel multicore processors that enable scaling of microprocessor systems means that many different supply voltages are becoming necessary on modern computer chips. External board-mounted voltage regulators have not kept up with these scaling demands.
Today, by introducing an unprecedented combination of magnetic materials, chip-stacking design and a 2.5-Dimension (2.5-D) packaging process, the team from Columbia University that has been funded in part by the SRC has demonstrated a new IVR solution in partnership with a research team from IBM, a member of SRC.
Based on their results, this new technology can deliver a substantial reduction in power consumption. In the U.S., for instance, data centers alone consume a substantial amount of the nation’s electricity. The new IVR technology could improve the efficiency of these data centers by 10 to 20 percent, providing estimated annual savings of more than $270 million in data center electricity costs and reduction of about 4 million metric tons of CO2 emissions per year.
“A key to further scaling is the ability to scale the energy storage elements required for these voltage regulators,” said Professor Ken Shepard, lead researcher for the team at Columbia. “By developing power converters that are small enough to be integrated on the same chip or in the same package as microprocessors, we can significantly improve computational performance per watt of power consumed.”
Historically, most of industry’s efforts have focused on improving transistor performance through process advances. As technology scaling saturates, future performance gains will rely on the ability to parallelize workloads across multiple cores on the same chip.
In order to sustain improvements in energy-constrained computational performance of digital systems, voltage converters operate by storing energy drawn from one supply voltage and then delivering this stored energy at a different supply voltage. Columbia’s IVRs enable the supply voltage of microprocessors to be throttled on nanosecond time scales, matching changes in workload.
While switched-inductor converters have been widely adopted as board level voltage regulators for their high efficiency and support of a continuous range of conversion ratios, they have not been effectively integrated on-chip because the required inductors have not — until now — been scalable to small enough dimensions without incurring a substantial penalty in conversion efficiency. For this reason, competing efforts in IVR development have focused on switched-capacitor converters, despite performance challenges with these converters.
Working with SRC member IBM to develop an integrated inductor that enables high-efficiency power conversion, the research team has provided all of the traditional advantages of a switched-inductor converter in a form factor that is small enough to integrate on-chip. Another SRC member, Intel Corporation, also has been engaged actively in research in this area.
“This technology is nearing industry adoption and can significantly benefit society while helping semiconductor companies to improve performance-per-watt for their products,” said Betsy Weitzman, SRC executive vice president. “End users will want products such as smartphones, laptops and servers to employ this technology because it will deliver reduced system power consumption and the potential for improved computational performance.”
Magnetic materials required of the power inductors are deposited as part of a custom process, integrated with traditional CMOS fabrication. This extra step allows integration of the voltage regulators directly onto an IC or into a chip stack, reducing complexity at the board level as well as providing high scalability.
More information about the research is published in the paper titled, “A 2.5D Integrated Voltage Regulator Using Coupled Magnetic Core Inductors on Silicon Interposer Delivering 10.8A/mm2,” presented today at the International Solid State Circuits Conference (ISSCC) in San Francisco at the session on Advances in Heterogeneous Integration. The paper is co-authored by Noah Sturcken, Michele Petracca, Ryan Davies, Ioannis Kymissis, Luca P. Carloni and Kenneth L. Shepard from Columbia, Angel V. Peterchev from Duke and Eugene J. O'Sullivan, Naigang Wang, Philipp Herget, Bucknell Webb, Lubomyr T. Romankiw, Robert Fontana, Gary M. Decad and William J. Gallagher from IBM.
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