IEEE Power Electronics Magazine - March 2022 - 19

power conversion electronics. The article describes some
prominent research highlights from both commercial practices
and academic frontiers, and provides insight on these
case study applications.
On the academic front, a joint paper " Vertical Stacked
LEGO-PoL CPU Voltage Regulator " by researchers from
Princeton University, Intel, and Dartmouth College, published
in the IEEE Transactions on Power Electronics [4],
presents a 48 V to 1 V merged-two-stage hybrid-switchedcapacitor
(SC) converter with a linear extendable group
operated point-of-load (LEGO-PoL) architecture for ultrahigh-current
microprocessors. It features 3D stacked packaging
and coupled inductors for miniaturized size and vertical
power delivery. This paper indicates that a vertical
stacked CPU voltage regulator is built and tested with air
and liquid cooling to offer a peak efficiency of 91.1% and a full
load efficiency of 79.2% at an output voltage of 1 V. The output
current capability reported is 450 A with air cooling and
780 A with liquid cooling. Claiming to be the first demonstration
of a 48 V-1 V CPU voltage regulator, the paper claims a
current density of over 1A/mm2 and an unprecedented power
density of 1,000 W/in3.
Granular microprocessor delivery has been gaining
attention both in the industry and academia. Researchers
from ZTH Zurich, Switzerland, have disclosed an onchip
SC converter enabling granular power delivery with
per-core regulation to achieve high efficiency, high power
density, fast response time, and high output power [5].
Implemented in a 32 nm SOI CMOS technology with deep
trench capacitors and a novel feed forward control, the onchip
switched capacitor voltage regulator (SCVR) provides
a 0.7-1.1 V output voltage from 1.8 V input, and achieves
85.1% maximum efficiency at 3.2 W/mm2 power density
with a sub-nanosecond response time. The maximum
output power reported is 10 W. This paper concludes that
on-chip SCVRs, which historically have been perceived as
being inefficient, low power, and difficult to regulate, are a
viable candidate to enable granular microprocessor power
delivery and per-core regulation.
In the last two decades, Tyndall National Institute, Cork,
Ireland, has demonstrated encouraging results in integrated
magnetics for PCB and on-chip applications. During
this period, the magnetics group at Tyndall has developed
innovative solutions in all areas of power magnetics
research, including design, material and process development,
micro-fabrication, electrical characterization, packaging
and reliability. In addition, the group is credited to be
the first to develop an optimization CAD tool for the design
of magnetic passive components on silicon, establish a magnetics
processing platform for prototyping on-silicon magnetics
and development of best-in class magnetic materials.
Combining thin-film magnetic materials with high switching
frequency (20 - 200 MHz), the researchers have demonstrated
integration of magnetics (inductors and transformers)
on silicon, designated MagIC, According to the
Institute website [6], to- date, the group has demonstrated
highest efficiency for a micro-inductor (93%), highest efficiency
micro-transformer (80%) and ultra-low loss high flux
density soft magnetic materials. This work is part of an EUfunded
FP7 project called PowerSwipe.
Similarly, startups like Ferric Inc., Empower Semiconductor,
and Enachip are further pushing the performance
envelope of integrated magnetics and PwrSoCs. Ferric, for
instance, has readied what it claims are the industry's first
single-chip power converters with on-chip thin-film magnetic
power inductors, offering industry leading current density.
The insatiable thirst for PSiPs and PwrSoCs will continue
to drive the performance of these two products to
new heights, setting new standards in efficiency, power
density, EMI, reliability, and other metrics. As more startups
enter the PwrSoC arena, integrated magnetics become
commercially available, and fabs are ready to deliver PwrSoCs,
the adoption of PwrSoCs will rise substantially during
the next several years, giving it the recognition it has
been seeking for more than a decade.
About the Author
Ashok Bindra (bindra1@verizon.net) received his M.S.
degree from the Department of Electrical and Computer
Engineering, Clarkson College of Technology (now Clarkson
University), Potsdam, New York, and his M.Sc. degree
in physics from the University of Bombay, India. He is the
editor-in-chief of IEEE Power Electronics Magazine and a
Member of the IEEE. He is a veteran freelance writer and
editor with more than 35 years of editorial experience covering
power electronics, analog/radio-frequency technologies,
and semiconductors. He has worked for leading electronics
trade publications in the United States, including
Electronics, EE Times, Electronic Design, Power Electronics
Technology, and RF Design.
References
[1] Arnold Alderman, " Update on PSMA Study of Power Supply in Package
Vs Power Supply on Chip, " PwrSoc 2008, Session 6: Monolithic Integration vs
System in Package.
[2] M. Shousha, D. Dinulovic, M. Brooks, M. Hofer, and M. Haug, " Design and
application considerations of packaging of DC-DC converter micromodules, "
in Proc. 2021 IEEE APEC, pp. 2318-2322.
[3] F. Meng, C. Wang, Z. Liu, K. Ma, D. Don, and K. S. Yeo, " Heterogeneous
integration: A promising technology to future integrated power conversion, "
IEEE Power Electron. Mag., Sep. 2021.
[4] J. Baek et al., " Vertical stacked LEGO-PoL CPU voltage regulator, " IEEE
Trans. Power Electron., Dec. 14, 2021, doi: 10.1109/TPEL.2021.3135386.
[5] T. M. Andersen et al., " A 10 W on-chip switched capacitor voltage regulator
with feedforward regulation capability for granular microprocessor
power delivery, " IEEE Trans. Power Electron., vol. 32, no. 1, Jan. 2017.
[6] Tyndall National Institute, Integrated Magnetics Website https://www.
tyndall.ie/integrated-magnetics-1
[7] Robert Gendron, " How Increasing Power and Advanced Cooling Techniques
Are Converging for AI, Supercomputing and Cloud Data Centers, "
Embedded Computing Design, OpenSystems Media, 10 February, 2020.
March 2022 z IEEE POWER ELECTRONICS MAGAZINE 19
https://www.tyndall.ie/integrated-magnetics-1 https://www.tyndall.ie/integrated-magnetics-1
IEEE Power Electronics Magazine - March 2022

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