36 The PCB Design Magazine • January 2016
Points to Remember:
• Tight coupling between adjacent planes
can be utilized to add planar capacitance
and dramatically reduce the AC imped-
ance at the high end.
• Planar capacitor laminate, also known as
embedded capacitor material, is becom-
ing a cost-effective solution to further im-
proved power integrity.
• Solid power and ground planes encompass
a distributed system of surprising com-
plexity.
• A distributed system involves the relation-
ship between the time delay of the system
and the rise-time of the signals.
• During the rising and falling edge, the lo-
cal planes and decaps cannot react before
the edge has vanished. This frequently re-
sults in a large noise spike.
• Repetitive pulse clocks tend to superim-
pose and build significant peaks.
• Avoid potential failure by comparing the
round-trip delay across the plane, to the
clock period.
• A "rough wave" is formed when a long,
slow oscillation is followed by a short and
fast oscillation.
• A combination of modifications to dielec-
tric thickness and dielectric constant of
the material in the ICD Stackup Planner,
together with an adjustment of plane size,
can usually establish the minimum reso-
nance for the configuration.
PCBDESIgN
References
1. Barry Olney's Beyond Design columns:
No One-Way Trips, The Dumping Ground, Los-
ing a Bit of Memory, Stackup Planning Parts
1-4, Material Selection for SERDES Design.
2. Henry Ott: Electromagnetic Compatibil-
ity Engineering
3. Howard Johnson: High-speed Signal Prop-
agation
4. Masanori Hashimoto and Raj Nair: Power
Integrity for Nanoscale Integrated Systems
5. The ICD Stackup and PDN Planner: www.
icd.com.au
Barry olney is managing
director of In-Circuit Design
Pty ltd (ICD), Australia. This
PCB design service bureau
specializes in board-level
simulation, and has developed
the ICD Stackup Planner and ICD PDn
Planner software. To read past columns,
or to contact olney, click here.
nanotechnologists at the university of Twente
research institute MeSA+ have discovered a new
fundamental property of electrical currents in very
small metal circuits. They show how electrons can
spread out over the circuit like waves and cause in-
terference effects at places where no electrical cur-
rent is driven. The geometry of the circuit plays a
key role in this so called nonlo-
cal effect. For designers of
quantum computers it is an ef-
fect to take account of.
Interference is a common
phenomenon in nature and oc-
curs when one or more propa-
gating waves interact coherently. Interference of
sound, light or water waves is well known, but also
the carriers of electrical current—electrons—can in-
terfere. It shows that electrons need to be consid-
ered as waves as well, at least in nanoscale circuits
at extremely low temperatures.
The researchers have demonstrated electron in-
terference in a gold ring with a diameter of only 500
nanometers. one side of the ring was connected to
a miniature wire through which an electrical cur-
rent can be driven. on the other side, the ring was
connected to a wire with a voltmeter attached to it.
now the researchers have
discovered a new way to af-
fect the dynamical nonlocali-
ty. understanding this funda-
mental effect is important for
future quantum information
processing.
Spooky Interference
at a Distance
beyond design
PLANE CRAzY, PART 2
