74 DESIGN007 MAGAZINE I NOVEMBER 2018
However, the inductance of laminates
depends on the combination of laminate and
copper thicknesses and frequency. At high
frequencies, the inductance is clearly pro
-
portional to dielectric thickness, which is the
primary power distribution benefit. Below
the skin cutoff frequency, the inductance gets
bigger with heavier copper. Thin laminates
also naturally suppress plane resonances. The
correlation is somewhat worse for shorted-
edge test cases because the causal SPICE mod-
els ignore and hybrid solvers only approxi-
mate for the impact of test-via antipads. To
get that level of correlation, you must use 3D
solvers
[5]
.
Acknowledgement
The DUT laminates and fabrication are
courtesy of DuPont, the network analyzer
personal loaner is courtesy of Keysight, and
the PowerSI simulations are courtesy of
Cadence. Special thanks to Jin-Hyun Hwang,
Tom Hilger for running the simulations, and
Brad Brim for his valuable comments and
guidance.
DESIGN007
References
1. I. Novak. (2017). "Quiet Power: Causal Power Plane
Models."
2. I. Novak, Y. Mori, & M. Resso. (2010). "Accuracy
Improvements of PDN Impedance Measurements in the
Low to Middle Frequency Range." DesignCon.
3. I. Novak. "Self and Transfer Impedances of Loss-less
Parallel Conductive Plates with One Capacitor."
4. Cadence Design Systems "Sigrity PowerSI."
5. I. Novak & J.R. Miller (2007). Frequency-Domain
Characterization of Power Distribution Networks. Artech
House, Section 2.4.
Istvan Novak is the principal signal
and power integrity engineer at Sam-
tec, with over 30 years of experience
in high-speed digital, RF, and analog
circuit and system design. He is a
Life Fellow of the IEEE, author of two
books on power integrity, and an instructor of signal and
power integrity courses. He also provides a website that
focuses on SI and PI techniques. To read past columns or
contact Novak, click here.
The heat produced by electronic devices does more
than annoy users. Heat-induced voids and cracking can
cause chips and circuits to fail.
Now a Stanford-led engineering team has developed a
way to not only manage heat, but help route it away from
delicate devices. Writing in
Nature Communications, the
researchers describe a thermal transistor—a nanoscale
switch that can conduct heat away from electronic com-
ponents and insulate them against its damaging effects.
"Developing a practical thermal transistor could be a
game changer in how we design electronics," said Senior
Author Kenneth Goodson, a professor of mechanical engi-
neering.
Researchers have been trying to develop heat switches
for years. Previous thermal transistors proved too big, too
slow and not sensitive enough for practical use. The chal-
lenge has been finding a nanoscale technology that could
toggle on and off repeatedly, have a large hot-to-cool
switching contrast and no moving parts.
Aditya Sood, a postdoctoral scholar with Goodson and
Pop and co-first author on the paper, likened the ther-
mal transistor to the thermostat in a car. When the car
is cold, the thermostat is off, preventing coolant
from flowing, and the engine retains heat. As the
engine warms, the thermostat opens and coolant
begins to move to keep the engine at an optimal
temperature.
Thinking about this process is crucial to design-
ing safer batteries. In a more distant future, the
researchers imagine that thermal transistors could
be arranged in circuits to compute using heat logic.
(Source: Stanford University)
How Can We Design Electronic Devices That Don't Overheat?
