60 DESIGN007 MAGAZINE I JULY 2019
est impedance. At 1 GHz, a further increase
of trace length to 10 mils in model 1D wors-
ens the impedance by 1 ohm versus model 1E.
Model 1A with the longest trace length of 20
mils and largest interconnection inductance (a
total series inductance of 0.95nH) experienc-
es additional 1-ohm impedance at 1 GHz com-
pared to the other two models.
Summary
It is crucial to minimize interconnection in-
ductance to achieve minimal impedance in the
decoupling capacitor and the PDN. Via-in-pad
shall be applied as an interconnection medium
to nullify the effects of trace length. Further-
more, power and ground planes shall be as-
signed closer to outer PCB layers that feature
decoupling capacitors to reduce stitching via
height.
DESIGN007
References
1. "High-speed PCB Layout Techniques," Texas Instru-
ments.
2. F. Carrio, V. Gonzalez, & E. Sanchis, "Basic Concepts
of Power Distribution Network Design for High-speed
Transmission,"
The Open Optics Journal, 5, pp. 51–61, 2011.
3. R. Keim, "PCB Layout Tips and Tricks: Minimizing De-
coupling Inductance," All About Circuits, July 26, 2018.
4. "Estimating the Connection Inductance of a Decou-
pling Capacitor," Learn EMC.
5. "Ultra-Low Impedance Measurements Using 2-Port
Measurements," Keysight Technologies.
6. "Auto Fixture Removal (AFR)," Keysight Technologies.
Chang Fei Yee is a hardware engineer with
Keysight Technologies. His
responsibilities include embedded
system hardware development, and
signal and power integrity analysis.
Figure 8. Plots of impedance (L) and series inductance (R) for models with varying trace length after de-embedding.
Scientists at Oak Ridge National Laboratory have de-
veloped a low-cost, printed, flexible sensor that can wrap
around power cables to precisely monitor electrical loads
from household appliances to support grid operations.
Using an inkjet printer, researchers deposited wires on a
flexible plastic substrate, then wove in a magnetic strip to
channel the flux produced by an electric current, making
the sensor suitable to install in tight spaces. When tested
on conductors in the lab and on a building HVAC unit, the
sensor measured responses of up to 90A of electrical cur
-
rent and is expected to exceed 500A in larger applications.
"These inexpensive sensors provide crucial, real-time
usage data needed to monitor and control devices, such
as smart HVAC and water heaters for better power grid effi-
ciency and resilience," said Pooran Joshi, a senior scientist
in the Materials Science and Technology Division at ORNL.
The team is currently testing new materials, electronics,
and packaging to increase the sensor's range and applica-
tions while keeping costs low.
(Source: Oak Ridge National Laboratory)
Wrap-around Sensors for the Grid
