Glossary
This section defines the terminology used in
the Ansys desktop help topics. Terms are listed in alphabetical order.
Glossary: A
A/D
See Analog-to-Digital.
ACPR
Adjacent channel power ratio.
Active Substrate
A hybrid or multichip module substrate formed from
a semiconductor. Termed active because components such as transistors
can be fabricated directly into the substrate.
Active Trimming
The process of trimming components such as resistors
while the circuit is under power. Such components are fabricated directly
onto the substrate of a hybrid or multichip module, and the trimming
is usually performed using a laser beam.
Active-High
A signal whose active state is considered to be a logic
1.
Active-Low
A signal whose active state is considered to be a logic
0.
Actuator
A transducer that converts an electronic signal into
a physical equivalent. For example, a loudspeaker is an actuator which
converts electronic signals into corresponding sounds.
Adaptive Hardware
Refers to devices which allow new design variations
to be "compiles" in real-time, which may be thought of as dynamically
creating subroutines in hardware (see also Virtual Hardware and Cache
Logic).
Additive Process
A process in which conducting material is added to
specific areas of a substrate. Groups of tracks, individual tracks, or
portions of tracks can be built up to precise thicknesses by iterating
the process multiple times with selective masking.
Address Bus
A unidirectional set of signals used by a computer
to point to memory locations in which it is interested.
Analog
A continuous value that most closely resembles the
real world and can be as precise as the measuring technique allows.
Analog Circuit
A collection of components used to generate or process
analog signals.
Analog-to-Digital (A/D)
The process of converting an analog value into its
digital equivalent.
Anisotropic Adhesive
Special adhesives which contain minute particles of
conductive material. These adhesives find particular application with
the flipped-chip techniques used to mount bare die on the substrates
of hybrids, multichip modules, or circuit boards. The conducting particles
are only brought in contact with each other at the sites where the raised
pads on the die are pressed down over their corresponding pads on the
substrate, thereby forming good electrical connections between the pads.
Anti-Fuse Technology
A programmable logic device technology in which conducting
paths (anti-fuses) are grown by applying signals of relatively high voltage
and current to the device's inputs.
Anti-Pad
The area of copper etched away around a via or a plated
through-hole on a power or negative signal plane, thereby preventing
an electrical connection being made to that plane.
Application-Specific Integrated Circuit (ASIC)
A device whose function is determined for a particular
application or group of applications.
Application-Specific Standard Part (ASSP)
Refers to an integrated circuit created by a device
manufacturer using ASIC technologies, and for these components to be
sold as standard parts to anybody who wants to buy them.
ASIC
See Application-Specific Integrated Circuit.
ASIC Cell
A logic function in the cell library defined by the
manufacturer of an application-specific integrated circuit.
Assertion-Level Logic
Special symbols which are used to more precisely indicate
the function of gates with active-low inputs.
ASSP
See Application-Specific Standard Part.
Asynchronous
A signal whose data is acknowledged or acted upon immediately,
irrespective of any clock signal.
Atto
Unit qualifier (symbol = a) representing one millionth
of one millionth of one millionth, or 10-18. For example, 3aS stands
for 3 x 10-18 seconds.
Attenuator
A passive device used to reduce signal strength while
maintaining proper input and output impedance.
Glossary: B
Backplane
The medium used to interconnect a number of circuit
boards. Typically refers to a special, heavy-duty printed or discrete
wired circuit board.
Ball Grid Array (BGA)
A packaging technology similar to a pad grid array,
in which a device's external connections are arranged as an array of
conducting pads on the base of the package. However, in the case of a
ball grid array, small balls of solder are attached to the conducting
pads.
Bandpass
The frequency limits between half-power points of a
signal or filter.
Bare Die
An unpackaged integrated circuit.
Base
Refers to the number of digits in a numbering system.
For example, the decimal numbering system is said to be base-10. May
also be referred to as the "radix".
Basic Cell
A pre-defined group of unconnected components that
is replicated across the surface of a gate array.
BER
Bit error rate.
BGA
See Ball Grid Array.
BiCMOS
A technology in which the function of each logic gate
is implemented using low-power CMOS, while the output stage is implemented
using high-drive bipolar transistors
Binary Encoding
A form of state assignment for state machines that
requires the minimum number of state variables.
BiNMOS
A relatively new low-voltage integrated circuit technology
in which complex combinations of bipolar and NMOS transistors are used
to form sophisticated output stages providing both high speed and low
static power dissipation.
Bi-quinary
A system which utilizes two bases, base-2 and base-5,
to represent decimal numbers. Each decimal digit is represented by the
sum of two parts, one of which has the value of decimal zero or five,
and the other the values of zero through four. The abacus is one practical
example of the use of a bi-quinary system.
Bit
Abbreviation of binary digit.
Bipolar Junction Transistor (BJT)
A family of transistors.
Blackbox
Same as N-Port.
Blind Via
A via that is only visible from one side of the substrate.
Bobble
A small circle used on the inputs to a logic gate symbol
to indicate an active-low input or control, or on the outputs to indicate
a negation (inversion) or a complementary signal. Some engineers prefer
to use the term bubble.
Bounce Pad
A special pattern etched onto the power or negative
signal plane of a microwire circuit board to be used in conjunction with
a laser beam which is employed to create blind vias. The laser beam evaporates
the epoxy forming the outer layers of the board and continues down to
the bounce pad which reflects, or bounces, it back up, thereby terminating
the via.
Braze
To unite or fuse two pieces of metal by heating, or
with a hard solder with a high melting point.
Bulk Storage
Refers to some form of media, typically magnetic, such
as tape or a disk drive which can be used to store large quantities of
information relatively inexpensively.
Buried Via
A via used to link conducting layers internal to a
substrate. Such a via is not visible from either side of the substrate.
Bundle
A set of signals related in some way that makes it
appropriate to group them together for ease of representation or manipulation.
May contain both scalar and vector elements; for example, {a,b,c,d[5:0]}.
Bus
A set of signals performing a common function and carrying
similar data. Typically represented using vector notation; for example,
address[7:0].
Byte
A group of eight binary digits, or bits.
Glossary: C
Capacitance
A measure of the ability of two adjacent conductors
separated by an insulator to hold a charge when a voltage differential
is applied between them. Capacitance is measured in units of Farads.
CDMA
Code division multiple access.
Cell Library
The collective name for the set of logic functions
defined by the manufacturer of an application-specific integrated circuit.
The designer decides which types of cells should be realized and connected
together to make the device perform its desired function.
Ceramic
An inorganic, nonmetallic material, such as alumina,
beryllia, steatite, or forsterite, which is fired at a high temperature
and is often used in electronics as a substrate or to create component
packages.
CGA
See Column Grid Array.
Channel
(1)The area between two arrays of basic cells in a
channeled gate array.
(2)The gap between the source and drain regions
in a MOS transistor.
Channeled Gate Array
Application-specific integrated circuit organized as
arrays of basic cells. The areas between the arrays are known as channels.
Channel-Less Gate Array
Application-specific integrated circuit organized as
a single large array of basic cells. May also be referred to as a "sea
of cells" or a "sea of gates" device.
Checksum
The final cyclic-redundancy-check value stored in a
linear feedback shift register (or software equivalent). Also known as
a "signature" in the guided-probe variant of functional test.
Chip
Popular name for an integrated circuit.
Chip-On-Board (COB)
A process in which unpackaged integrated circuits are
physically and electrically attached to a circuit board, and are then
encapsulated with a "glob" of protective material such as epoxy.
Chip-On-Chip (COC)
A process in which unpackaged integrated circuits are
mounted on top of each other. Each die is very thin and it is possible
to have over a hundred dies forming a 3D cube.
Chip-On-Flex (COF)
Similar to chip-on-board (COC), except that the unpackaged
integrated circuits are attached to a flexible printed circuit.
Circuit Board
The generic name for a wide variety of interconnection
techniques, which include rigid, flexible, and rigid-flex boards in single-sided,
double-sided, multilayer, and discrete wired configurations.
CMOS
Logic gates constructed using both NMOS and PMOS transistors
connected in a complementary manner.
Coaxial Cable
A conductor in the form of a central wire surrounded
first by a dielectric (insulating) layer, and then by a conducting tube
which serves to shield the central wire from external interference.
Coefficient of Thermal Expansion
Defines the amount a material expands and contracts
due to changes in temperature. If materials with different coefficients
of thermal expansion are bonded together, changes in temperature will
cause shear forces at the interface between them.
Cofired Ceramic
A substrate formed from multiple layers of "green"
ceramic that are bonded together and fired at the same time.
Column Grid Array (CGA)
A packaging technology similar to a pad grid array,
in which a device's external connections are arranged as an array of
conducting pads on the base of the package. However, in the case of a
column grid array, small columns of solder are attached to the conducting
pads.
Combinatorial
A digital function whose output value is directly related
to the current combination of values on its inputs. Also known as combinational.
Compiled Cell Technology
A technique used to create portions of a standard cell
application-specific integrated circuit. The masks used to create components
and interconnections are directly generated from Boolean representations
using a silicon compiler. May also be used to create data-path functions
and memory functions.
Complementary Output
Refers to a function with two outputs carrying complementary
logical values. One output is referred to as the true output and the
other as the complementary output.
Complex Programmable Logic Device (CPLD)
A device that contains a number of PLA or PAL functions
sharing a common programmable interconnection matrix.
Component
Components are items placed on schematics and layouts
to represent electrical elements and sub circuits. The component information
defines a signal-processing function or source, or secondarily a data
source, data channel, or similar entity. Components have pins for connections,
bitmaps in the project tree, and properties for simulation. The information
that constitutes a component includes its component chooser bitmap, schematic
symbol, layout footprint, pin properties, parameters and parameter values,
and netlist string definition. A component can be associated with more
than one simulation if it can be analyzed in more than one simulator.
Computer-Generated Hologram (CGH)
Refers to a slice of quartz or similar material into
which three-dimensional patterns are cut using a laser. The angles of
the patterns cut into the quartz are precisely calculated for use in
the optical communication strategy known as holographic interconnect.
All of these calculations are performed by a computer, and the laser
used to cut the three-dimensional patterns into the quartz is also controlled
by a computer. Thus, the slice of quartz is referred to a computer-generated
hologram.
Conductive Ink Technology
A technique in which tracks are screen printed directly
onto the surface of a circuit board using a conductive ink.
Configurable Hardware
A product whose function may be customized once or
a very few times (see also Reconfigurable Hardware, Remotely Reconfigurable
Hardware, Dynamically Reconfigurable Hardware, and Virtual Hardware).
Conjunction
Propositions combined with an AND operator; for example,
"You have a parrot on your head AND you have a fish in your ear." The
result of a conjunction is true if all the propositions comprising that
conjunction are true.
Conversion Loss
The ratio in dB of the IF output of a mixer to the
RF input power. All conversion loss measurements and specification are
normally based on the mixer being terminated on all ports and a stated
LO signal power level being applied.
Cost Function
In an optimization setup, a cost function is based
on goal values specified for at least one solution quantity. Optimetrics
changes the design parameter values to fulfill the cost function.
CPLD
See Complex Programmable Logic Device.
CRC
See Cyclic Redundancy Check.
CSIC
See Customer-Specific Integrated Circuit.
Customer-Specific Integrated Circuit (CSIC)
An alternative and possibly more accurate name for
an ASIC, but this term is rarely used in the industry and shows little
indication of finding favor with the masses.
Chemical Vapor Deposition (CVD)
A process for growing thin films on a substrate, in
which a gas containing the required molecules is converted into a plasma
by heating it to extremely high temperatures using microwaves. The plasma
carries atoms to the surface of the substrate where they are attracted
to the crystalline structure of the substrate. This underlying structure
acts as a template. The new atoms continue to develop the structure to
build up a layer on the substrate's surface.
Chemical Vapor Infiltration (CVI)
A process similar to chemical vapor deposition (CVD)
but, in this case, the process commences by placing a crystalline powder
of the required substance in a mold. Additionally, thin posts, or columns,
can be pre-formed in the mold, and the powder can be deposited around
them. When exposed to the same plasma as used in the CVD technique, the
powder coalesces into a polycrystalline mass. After the CVI process has
been performed, the posts can be dissolved leaving holes through the
crystal for use in creating vias. CVI processes can produce layers twice
the thickness of those obtained using CVD techniques at a fraction of
the cost.
CW
Continuous wave; refers to an unmodulated sine-wave
signal.
Cyclic Redundancy Check (CRC)
A calculation used to detect errors in data communications,
typically performed using a linear feedback shift register. Similar calculations
may be used for a variety of other purposes such as data compression.
Glossary: D
D/A
See Digital-to-Analog.
Data Bus
A bi-directional set of signals used by a computer
to convey information from a memory location to the central processing
unit and vice versa. More generally, a set of signals used to convey
data between digital functions.
Data-Path Function
A well-defined function such as an adder, counter,
or multiplier used to process digital data.
dBm
Power level relative to 1mV rms.
DC Balance
Stream of data encoded to ensure an equal balance of
1 or 0 . 8b10b encoding has been developed to ensure DC balancing.
DC Coupling
A method of coupling two different circuits together,
allowing them to share both the static DC and varying AC characteristics
of a signal.
Decoder (digital)
A logic function that uses a binary value, or address,
to select between a number of outputs and to assert the selected output
by placing it in its active state.
Deep Sub-Micron
Typically taken to refer to integrated circuits containing
structures which are smaller than 0.5 microns.
DeMorgan Transformation
The transformation of a Boolean expression into an
alternate, and often more convenient, form.
Design
Designs are the building blocks of projects, and can
be Circuit designs or 3D planar EM models. Designs consist of schematics
or geometrical models, model data, solution setup information, output
graphs and tables, and other pieces of information that go into describing
simulation of electrical circuits. A design is the largest single simulatable
entity in a project.
Design Variation
A single combination of variable values that is solved
during a parametric or optimization setup.
Device
A discrete, separate electrical entity such as a diode,
a capacitor or a packaged transistor.
Die
(1)An unpackaged integrated circuit. In this case,
the plural of die is also die (in much the same way that "a shoal of
herring" is the plural of "herring"). (2)A piece of metal with a design
engraved or embossed on it for stamping onto another material, upon which
the design appears in relief.
Die Separation
The process of separating individual die from the wafer
by marking the wafer with a diamond scribe and fracturing it along the
scribed lines.
Die Stacking
A technique used in specialist applications in which
several bare die are stacked on top of each other to form a sandwich.
The die are connected together and then packaged as a single entity.
Dielectric Layer
(1) An insulating layer used to separate two signal
layers.
(2) An insulating layer used to modify the electrical characteristics
of an MCM-D substrate.
Diffusion Layer
The surface layer of a piece of semiconductor into
which impurities are diffused to form P-type and N-type material. In
addition to forming components, the diffusion layer may also be used
to create embedded traces.
Digital
A value represented as being in one of a finite number
of discrete states called quanta. The accuracy of a digital value is
dependent on the number of quanta used to represent it.
Digital Circuit
A collection of logic gates used to process or generate
digital signals.
Digital Signal Processor (DSP)
A primarily digital component used to process either
digital or analog signals. In the case of the latter, the signal may
first be conditioned, then converted into a digital equivalent using
an analog-to-digital (A/D) converter function. The signal conditioning
and A/D functions may either be external to the DSP or resident in the
device. A typical DSP application might be the compression/decompression
of video data.
Digital-to-Analog (D/A)
The process of converting a digital value into its
analog equivalent.
Diode
A two-terminal device that only conducts electricity
in one direction; in the other direction it behaves like an open switch.
The term diode is typically taken to refer to a semiconductor device,
although alternative implementations such as vacuum tubes are available.
Diode-Transistor Logic (DTL)
Logic gates implemented using particular configurations
of diodes and bipolar junction transistors. For the majority of today's
designers, diode-transistor logic is of historical interest only.
Discrete Device
Typically taken to refer to an electronic component
such as a resistor, capacitor, diode, or transistor that is presented
in an individual package. More rarely, the term may be used in connection
with a simple integrated circuit containing a small number of primitive
gates.
Discrete Wire Board (DWB)
A form of circuit board in which a special computer-controlled
wiring machine ultrasonically bonds extremely fine insulated wires into
the surface layer of the board. This discipline has enjoyed only limited
recognition, but may be poised to emerge as the technology-of-choice
for high-speed designers.
Discrete Wire Technology
The technology used to fabricate discrete wire boards.
Doping
The process of inserting selected impurities into a
semiconductor to create P-type or N-type material.
Double-Sided
A printed circuit board with tracks on both sides
DPSK
Differential phase-shift keying.
DQPSK
Differential quadrature phase-shift keying.
DRAM
See Dynamic RAM.
DSP
See Digital Signal Processor.
DTL
See Diode-Transistor Logic.
DUT
Device under test.
Dynamic Flex
A type of flexible printed circuit which is used in
applications that are required to undergo constant flexing such as ribbon
cables in printers.
Dynamic RAM (DRAM)
A memory device in which each cell is formed from a
transistor-capacitor pair. Called dynamic because the capacitor loses
its charge over time, and each cell must be periodically recharged if
it is to retain its data.
Glossary: E
E2PROM
See electrically Erasable Programmable Read-Only
Memory.
EBE
See Electron Beam Epitaxy.
ECL
See Emitter-Coupled Logic.
Edge port
A place in a layout or footprint geometry through which
excitation signals enter and leave the structure.
Edge-Sensitive
An input that only affects a function when it transitions
from one logic value to another.
EEPROM
See electrically Erasable Programmable Read-Only
Memory.
electrically Erasable Programmable Read-Only Memory
(EEPROM or E2PROM)
A memory device whose contents can be electrically
programmed by the designer. Additionally, the contents can be electrically
erased allowing the device to be reprogrammed. Also known as EEPROM and E2PROM.
Electromigration
(1)A process in which structures on an integrated circuit's
substrate are eroded by the flow of electrons in much the same way as
land is eroded by a river (also known as subatomic erosion). (2)The process
of forming transistor-like regions in a semiconductor using an intense
magnetic field.
Electron Beam Epitaxy (EBE)
A technique for creating thin films on substrates in
precise patterns, in which the substrate is first coated with a layer
of dopant material before being placed in a high vacuum. A guided beam
of electrons is fired at the substrate causing the dopant to be driven
into it, effectively allowing molecular-thin layers to be "painted" onto
the substrate where required.
Electron Beam Lithography
An integrated circuit fabrication process in which
fine beams of electrons are used to draw extremely high-resolution patterns
directly into the resist without the use of a mask.
Electro-Static Discharge (ESD)
The process of moving around can generate static electricity.
The term electro-static discharge refers to a charged person, or object,
discharging static electricity. Although the current associated with
such a static charge is low, the electric potential can be in the millions
of volts and can severely damage electronic components. CMOS devices
are particularly prone to damage from static electricity.
EM
Electromagnetic.
Emitter-Coupled Logic (ECL)
Logic gates implemented using particular configurations
of bipolar junction transistors.
Enzyme
One of numerous complex proteins which are produced
by living cells and catalyze biochemical reactions at body temperatures.
EPROM
See Erasable Programmable Read-Only Memory.
Equivalent Gate
A concept in which each type of logic function is assigned
an equivalent gate value for the purposes of comparing functions and
devices. However, the definition of an equivalent gate varies depending
on who you're talking to.
Equivalent Integrated Circuit
A concept used to compare the component density supported
by diverse interconnection technologies such as circuit boards, hybrids,
and multichip modules
Erasable Programmable Read-Only Memory (EPROM)
A memory device whose contents can be electrically
programmed by the designer. Additionally, the contents can be erased
by exposing the die to ultraviolet light through a quartz window mounted
in the top of the component's package.
ESD
See Electro-Static Discharge.
Etching
The process of selectively removing any material not
protected by a resist using an appropriate solvent or acid. In some cases
the unwanted material is removed using an electrolytic process.
Eutectic Bond
A bond formed when two pieces of metal, or metal-coated
materials, are pressed together and vibrated at ultrasonic frequencies.
Euler Angles
Euler angles are used in Ansoft software to carry out
a coordinate transformation from one coordinate system to another. The
Swiss mathematician and physicist Leonhard Euler first developed the
classical rotation theorem to describe rotations in 3D space. The angles
used are Euler angles and can be used to describe any 3D rotation. These
angles, given by (ö, è, ø) represent a series of sequential rotations
about two axis of the coordinate system. The first rotation (ö) represents
a rotation about the Z-axis of the source coordinate system (X, Y, Z)
which results in an intermediate coordinate system denoted by (X'', Y'',
Z''). The second rotation (è) represents a rotation of the intermediate
coordinate system about the X''-axis, again resulting in an intermediate
coordinate system denoted by (X', Y', Z'). The third and final rotation
(ø) represents a rotation about the Z'-axis of the intermediate coordinate
system. The final rotation completes the rotation and results in the
"target" coordinate system denoted (X, Y, Z).
For further information see, Eric W. Weisstein, "Euler
Angles." From MathWorld - A Wolfram Web Resource.
http://mathworld.wolfram.com/EulerAngles.html .
Eye Diagram
Eye diagrams are commonly used to analyze signal integrity
issues with communications channels. The bits are superimposed at unit
intervals representing the duration of each bit.
Eye Mask
The size of the eye opening in the center of an eye
diagram indicates the amount of voltage and timing margin available to
sample this signal. Thus, for a particular electrical interface, a fixed
reticule or window could be placed over the eye diagram showing how the
actual signal compares to minimum criteria window, know as the eye mask.
If a margin rectangle with width equal to the required timing margin
and height equal to the required voltage margin fits into the opening,
then the signal has adequate margins. Voltage margin can often be traded
off for timing margin.
Glossary: F
Fan-Out Via
In the case of surface mount devices attached to double-sided
or multilayer boards, each component pad is usually connected by a short
length of track to a via which forms a link to other conducting layers,
and this via is known as a fan-out via. The term fan-out via is generally
also taken to include any vias that fall inside the device's footprint
(under the body of the device). Some designers attempt to differentiate
these vias from those that fall outside the device's footprint by referring
to them as fan-in vias, but this is not an industry-standard term.
Falling-Edge
A transition from a logic 1 to a logic 0. Also known
as a negative edge.
Falltime
The time it takes for a waveform to transition from
the high logic state to the low logic state. Falltime is usually measured
from 90% of the total signal swing to 10% of the signal swing.
Fan-In and Fan-Out Vias
In the case of surface mount devices attached to double-sided
or multilayer boards, each component pad is usually connected by a short
length of track to a via which forms a link to other conducting layers,
and this via is known as a fan-out via. The term fan-out via is generally
also taken to include any vias that fall inside the device’s footprint
(under the body of the device). Some designers attempt to differentiate
these vias from those that fall outside the device’s footprint by referring
to them as fan-in vias, but this is not an industry-standard term.
Femto
Unit qualifier (symbol = f) representing one thousandth
of one millionth of one millionth, or 10-15. For example, 3fS stands
for 3 x 10-15 seconds.
FET
See Field-Effect Transistor.
Field-Effect Transistor (FET)
A transistor whose control, or gate, signal creates
an electro-magnetic field which turns the transistor ON or OFF.
Field-Programmable Gate Array (FPGA)
A programmable logic device which is more versatile
than traditional programmable devices such as PALs and PLAs, but less
versatile than an application-specific integrated circuit. Some field-programmable
gate arrays use fuses such as those found in programmable logic devices,
but others are based on SRAM equivalents.
Field-Programmable Interconnect Chip (FPIC)
An alternative, proprietary name for a field-programmable
interconnect device (FPID).
Field-Programmable Interconnect Device (FPID)
A device which is used to connect logic devices together,
and which can be dynamically reconfigured in the same way as standard
SRAM-based FPGAs. Because each FPID may have around 1,000 pins, only
a few such devices are typically required on a circuit board.
Filter
Filters are used to block out undesired frequencies.
There are two types of filters: band pass and rejection. A band pass
filter permits only the desired range to pass through, while the rejection
filter attenuates an undesired range of frequencies.
Firmware
Refers to programs, or sequences of instructions, that
are hard-coded into non-volatile memory devices.
First-In First Out (FIFO)
A memory device in which data is read out in the same
order that it was written in.
Flash (e.g., Gold Flash)
An extremely thin layer of gold with a thickness measured
on the molecular level which is either electroplated or chemically plated
onto a surface.
FLASH Memory
An evolutionary technology that combines the best features
of the EPROM and E2PROM technologies. The name FLASH is derived from
the technology's fast reprogramming time compared to EPROM.
Flex
See Flexible Printed Circuit.
Flexible Printed Circuit (FPC or Flex)
A specialist circuit board technology, often abbreviated
to "flex", in which tracks are printed onto flexible materials. There
are a number of flavors of flex, including static flex, dynamic flex,
and rigid flex.
Flipped Chip
A generic name for processes in which unpackaged integrated
circuits are mounted directly onto a substrate with their component-sides
facing the substrate.
Flipped TAB
A combination of flipped chip and tape automated bonding.
Footprint
The area occupied by a device mounted on a substrate.
Fourier Analysis
A mathematical procedure used to determine the collection
of sine waves (differing in frequency and amplitude) that is necessary
to make up the square-wave pattern under consideration.
FPC
See Flexible Printed Circuit.
FPGA
See Field-Programmable Gate Array.
FPIC
See Field-Programmable Interconnect Chip.
FPID
See Field-Programmable Interconnect Device.
FR4
The most commonly used insulating base material for
circuit boards. FR4 is made from woven glass fibers which are bonded
together with an epoxy. The board is cured using a combination of temperature
and pressure which causes the glass fibers to melt and bond together,
thereby giving the board strength and rigidity. The first two characters
stand for "Flame Retardant". FR4 is technically a form of fiberglass,
and some people do refer to these composites as fiberglass boards or
fiberglass substrates, but not often.
Free-Space Optical Interconnect
A form of optical interconnect in which laser-diode
transmitters communicate directly with photo-transistor receivers without
employing optical fibers or optical waveguides.
Full Custom
An application-specific integrated circuit in which
the designer has complete control over every mask layer used to fabricate
the device. The manufacturer does not provide a cell library or pre-fabricate
any components on the substrate.
Functional Latency
Refers to the fact that, at any given time, only a
portion of the logic functions in a device or system are typically active
(doing anything useful).
Functional Test
A test strategy in which signals are applied to a circuit's
inputs, and the resulting signals which are observed on the circuit's
outputs are compared to known good values.
Fuse
See Fusible-Link Technology.
Fusible-Link Technology (Fuse)
A programmable logic device technology which employs
links called fuses. Individual fuses can be removed by applying pulses
of relatively high voltage and current to the device's inputs.
Fuzz-Button
A small ball of fibrous gold used in one technique
for attaching components such as multichip modules to circuit boards.
Fuzz-buttons are inserted between the pads on the base of the package
and their corresponding pads on the board. When the package is forced
against the board, the fuzz-buttons compress to form good electrical
connections. Even when the pressure is removed, the fuzz-buttons act
in a similar manner to Velcro and continue to hold the component in place.
One of the main advantages of the fuzz-button approach is that it allows
broken devices to be quickly removed and replaced. Even though fuzz-button
technology would appear to be inherently unreliable, it is used in such
devices as missiles, so one can only assume that it is fairly robust.
Glossary: G
Gain
The ratio of the power output to the power input of
the amplifier in dB. The gain is specified in the linear operating range
of the amplifier where a 1 dB increase in input power gives rise to a
1 dB increase in output power. Gain = 20*log(S21)
Gate Array
An application-specific integrated circuit in which
the manufacturer pre-fabricates devices containing arrays of unconnected
components organized in groups called basic cells. The designer specifies
the function of the device in terms of cells from the cell library and
the connections between them, and the manufacturer then generates the
masks used to create the metallization layers.
Glue Logic
Simple logic gates used to interface more complex functions
together.
Gold Flash
An extremely thin layer of gold with a thickness measured
on the molecular level which is either electroplated or chemically plated
onto a surface.
Goal
In an optimization setup, a goal is the value of a
solution quantity that you want to be achieved during the optimization.
A goal is represented as one row in the cost function table. Each cost
function defined in an optimization setup must include at least one goal.
Gray Code
A sequence of binary values in which each pair of adjacent
values differs by only a single bit; for example, 00, 01, 11, 10.
Green Ceramic
Unfired, malleable ceramic.
Ground Bounce
Momentary noise on the device negative signal plane
causing a 0 signal to erroneously be seen as a 1. Ground bounce is caused
by simultaneously switching outputs (SSO).
Guard Condition
A Boolean expression associated with a state transition
in a state diagram or state table. The expression must be satisfied for
that state transition to be executed.
Guided Probe
A form of functional test in which the operator is
guided in the probing of a circuit to isolate a faulty component or track.
Guided-Wave
A form of optical interconnect, in which optical waveguides
are fabricated directly on the substrate of a multichip module. These
waveguides can be created using variations on standard opto-lithographic
thin-film processes.
Glossary: H
Hard Macro (Macro Cell)
A logic function defined by the manufacturer of an
application-specific integrated circuit. The function is described in
terms of the simple functions provided in the cell library and the connections
between them. The manufacturer also defines how the cells forming the
macro will be assigned to basic cells and the routing of tracks between
the basic cells.
Hardware
Generally understood to refer to any of the physical
portions constituting an electronic system, including components, circuit
boards, power supplies, cabinets, and monitors.
Harmonic
Integer multiples of the fundamental frequency of interest
commonly produced by a non-linear amplifier.
Harmonic Balance
A frequency domain analysis technique for simulating
nonlinear circuits and systems. This method assumes the input stimulus
consists of a relatively few steady state sinusoids. Therefore the solution
can be expressed as a sum of steady state sinusoids that includes the
input frequencies in addition to any significant harmonics or mixing
terms. A circuit with a single input source will require a single tone
HB simulation. The harmonic balance simulation is ideal for situations
where transient simulation methods are problematic, such as:
- Components modeled in frequency domain, for
instance (dispersive) transmission lines
- Circuit time constants large compared to period
of simulation frequency
- Circuits with lots of reactive components
Harmonic balance methods, therefore, are the best choice
for most microwave circuits excited with sinusoidal signals (e.g., mixers,
power amplifiers).
Harmonic Tuning
Impedance-matching at the harmonic frequencies for
enhanced performance and efficiency.
Hertz (Hz)
Unit of frequency. One Hertz equals one cycle, or one
oscillation, per second.
Heterojunction
The interface between two regions of dissimilar semiconductor
materials. The interface of a hetrojunction has naturally occurring electric
fields which can be used to accelerate electrons, and transistors created
using hetrojunctions can switch much faster than their counterparts of
the same size.
Hexadecimal
Base-16 numbering system. Each hexadecimal digit can
be directly mapped onto four binary digits, or bits.
High Impedance State
The state on a signal that is not being driven by any
value. A high-impedance state is indicated by the character Z.
Holographic Interconnect
A form of optical interconnect based on a thin slice
of quartz, into which three-dimensional images are cut using a laser
beam. Thus, the quartz is referred to as a computer-generated hologram,
and this interconnection strategy is referred to as holographic.
Homojunction
An interface between two regions of semiconductor having
the same basic composition but opposing types of doping. Homojunctions
dominate current processes because they are easier to fabricate than
heterojunctions.
Hybrid
An electronic sub-system in which a number of integrated
circuits (packaged and/or unpackaged) and discrete components are attached
directly to a common substrate. Connections between the components are
formed on the surface of the substrate, and some components such as resistors
and inductors may be fabricated directly onto the substrate.
Hydrogen Bond
The electrons in a water molecule are not distributed
equally, because the oxygen atom is a bigger, more robust fellow which
grabs more than its fair share. The end result is that the oxygen atom
has an overall negative charge, while the two hydrogen atoms are left
feeling somewhat on the positive side. This unequal distribution of charge
means that the hydrogen atoms are attracted to anything with a negative
bias; for example, the oxygen atom of another water molecule. The resulting
bond is known as a hydrogen bond.
Hz
See Hertz.
Glossary: I
IBIS
IBIS (I/O Buffer Information Specification) is a standard
for electronic behavioral specifications of integrated circuit input/output
analog characteristics. The core of an IBIS model is a table of current
versus voltage and I/O switching timing information. Xilinx IBIS models
contain tables for typical, slow/MIN (weak transistors, high temperature,
low voltage) and fast/MAX (strong transistors, low temperature, high
voltage) process corners. IBIS models are derived from SPICE simulation
results and/or lab measurements. The benefit for IBIS model user is fast
and accurate simulation while preserving IC vendors intellectual property
(information about circuit and process details).
IC
See Integrated Circuit.
ICR
See In-Circuit Reconfigurable.
Impedance
The resistance to the flow of current caused by resistive,
capacitive, or inductive devices (or undesired elements) in a circuit.
Impedance Matching
Function of ensuring that the impedance of the transmitter,
the receiver, and the transmission line are identical. Mismatched impedances
could result in signal reflections, ringing, overshoot, undershoot, and
stairstep waveforms.
Incident Voltage
The user specified voltage at an input.
In-Circuit Reconfigurable (ICR)
An SRAM-based, or similar component which can be dynamically
reprogrammed on-the-fly while remaining resident in the system.
Inductance
A property of a conductor that allows is to store energy
in a magnetic field which is induced by a current flowing through it.
Inductance is measured in units of Henries (the base unit is a Henry).
Insertion Loss
Insertion Loss (dB) is defined as the drop in power
as a signal enters an RF component. This value not only includes the
reflected incoming signal, but also the attenuation of the component.
In-System Programmable (ISP)
An E2-based, FLASH-based, or similar component which
can be reprogrammed while remaining resident on the circuit board.
Integrated Circuit (IC)
A device in which components such as resistors, capacitors,
diodes, and transistors are formed on the surface of a single piece of
semiconductor.
Ion
A particle formed when an electron is added to, or
subtracted from, a neutral atom or group of atoms.
Ion Implantation
A process in which beams of ions are directed at a
semiconductor to alter its type and conductivity in certain regions.
Isolation
The ratio (expressed in dB) of the power level at one
port compared to the resulting power level of the output port.
ISP
See In-System Programmable.
Glossary: J
JEDEC
See Joint Electronic Device Engineering Council.
Jitter
The jitter of a periodic signal is the delay between
the expected transition of the signal and the actual transition. Jitter
is a zero mean random variable. When worst case analysis is undertaken
the maximum value of this random variable is used.
Jitter Tolerance
Jitter tolerance is defined as the peak-to-peak amplitude
of sinusoidal jitter applied on the input that causes a predefined, acceptable
loss at the output. For example jitter applied to the input of an OC-N
equipment interface that causes an equivalent 1dB optical power penalty.
Jitter Transfer
Jitter transfer is defined as the ratio of jitter on
the output of a device to the jitter applied on the input of the device,
versus frequency. Jitter transfer is important in applications where
the system is utilized in a loop-timed mode, where the recovered clock
is used as the source of the transmit clock.
Joint Electronic Device Engineering Council (JEDEC)
A council which creates, approves, arbitrates, and
oversees industry standards for electronic devices. In programmable logic,
the term JEDEC refers to a textual file containing information used to
program a device. The file format is a JEDEC approved standard and is
commonly referred to as a JEDEC file.
Jumper
A small piece of wire used to link two tracks on a
circuit board.
Glossary: K
Karnaugh Map
A graphical technique for representing a logical function.
Karnaugh maps are often useful for the purposes of minimization.
Kelvin Scale of Temperature
A scale of temperature which was invented by the British
mathematician and physicist William Thomas, first Baron of Kelvin. Under
the Kelvin, or absolute, scale of temperature, 0 K (corresponding to
-273oC) is the coldest possible temperature and is known as absolute
zero.
Kilo
Unit qualifier (symbol = K) representing one thousand,
or 103. For example, 3KHz stands for 3 x 103 Hertz.
Kirchhoff's current law
The sum of all currents entering a node is equal to
the sum of all currents leaving the node.
Kirchhoff's voltage law
The directed sum of the electrical potential differences
around a circuit must be zero.
Glossary: L
Laminate
A material constructed from thin layers or sheets.
Often used in the substrate of circuit boards.
Large-Scale Integration (LSI)
Refers to the number of logic gates in a device. By
one convention, large-scale integration represents a device containing
100 to 999 gates.
Laser Diode
A special semiconductor diode which emits a beam of
coherent light.
Last-In First-Out (LIFO)
A memory device in which data is read out in the reverse
order to which it was written in.
Latch-Up Condition
A condition in which a circuit draws uncontrolled amounts
of current, and certain voltages are forced, or "latched-up", to some
level. Particularly relevant in the case of CMOS devices which can latch-up
if their operating conditions are violated.
Lateral Thermal Conductivity
Good lateral thermal conductivity means that the heat
generated by components mounted on a substrate can be conducted horizontally
across the substrate and out through its leads.
Layers (and Stackup)
Layers are used in the layout editor to organize and
isolate sets of geometry or other visual indicators. Signal, Negative
Signal, and Dielectric are common physical layers, while Symbol (to show
component symbols in layout), Error, and Ratsnest (to show connectivity)
are non-physical layers. The stackup contains additional properties of
the physical layers, such as material, thickness, and elevation. Geometrical
information on these layers is used to generate masks for manufacturing.
LDMOS
Laterally diffused metal oxide semiconductor.
Lead
(1) A metallic element (chemical symbol Pb).
(2) A metal
conductor used to provide a connection from the inside of a device package
to the outside world for soldering or other mounting techniques. Leads
are also commonly called pins.
Lead Frame
A metallic frame containing leads and a base to which
an unpackaged integrated circuit is attached. After encapsulation, the
outer part of the frame is cut away and the leads are bent into the required
shapes.
Lead Through-Hole (LTH)
A technique for populating circuit boards in which
component leads are inserted into plated through-holes. Often abbreviated
to "through-hole" or "thru-hole". When all of the components have been
inserted, they are soldered to the board, usually using a wave soldering
technique.
Level-Sensitive
An input whose effect on a function depends only on
its current logic value or level, and is not directly related to it transitioning
from one logic value to another.
LFSR
See Linear Feedback Shift Register.
Library
A library is a collection of one or more components
or component dependencies (materials, symbols, footprints, or padstacks)
stored in a container file. A library must be configured to a circuit
before use, either by the user (manually) or by loading technology files
(automatically). User libraries and Personal libraries are used to add
foundry support, user defined models, and any custom set of components
or simulation models. See the Library Overview topic for more information.
LIFO
See Last-In First-Out.
Limiting Level
The input power level when the output power is goes
into compression and no longer becomes linear.
Line
Used to refer to the width of a track; for example,
"This track has a line-width of 0.12mm."
Linear Feedback Shift Register (LFSR)
A shift register whose data input is generated as an
XOR or XNOR of two or more elements in the register chain.
Linearity
Describes how closely an output signal is to a perfectly scaled
multiple of a corresponding input signal.
Load Pull
Automated measurement of RF performance of a device
under test (at a constant frequency) by varying the source and load impedance
presented to the device
Logic Function
A mathematical function that performs a digital operation
on digital data and returns a digital value.
Logic Gate
The physical implementation of a logic function.
Logic Synthesis
A process in which a program is used to optimize the
logic used to implement a design.
Low-Fired Cofired
Similar in principle to standard cofired ceramic substrate
techniques. However, low-fired cofired uses modern ceramic materials
with compositions that allow them to be fired at temperatures as low
as 650oC to 750oC. Firing at these temperatures in an inert atmosphere
such as nitrogen allows non-refractory metals such as copper to be used
to create tracks.
LSI
See Large-Scale Integration.
LTH
See Lead Through-Hole.
Glossary: M
Mask Programmable
A device such as a read-only memory which is programmed
during its construction using a unique set of masks.
Maximal Displacement
A linear feedback shift register whose taps are selected
such that changing a single bit in the input data stream will cause the
maximum possible disruption to the register's contents.
Maximal Length
A linear feedback shift register that sequences through
(2n - 1) states before returning to its original value.
Maxterm
The logical OR of the inverted variables associated
with an input combination to a logical function.
MBE
See Molecular Beam Epitaxy.
MCM
See Multichip Module.
Medium-Scale Integration (MSI)
Refers to the number of logic gates in a device. By
one convention, medium-scale integration represents a device containing
13 to 99 gates.
Meg
Unit qualifier (symbol = M) representing one million,
or 106. For example, 3MHz stands for 3 x 106 Hertz.
Metallization Layer
A layer of conducting material on an integrated circuit
that is selectively deposited or etched to form connections between logic
gates. There may be several metallization layers separated by dielectric
(insulating) layers.
Metal-Oxide Semiconductor (MOS)
A family of transistors where the controlling terminal
is connected to a plate that is separated from the semiconduxtor by an
insulating layer. This plate was originally made out metal (we now use
polysilicon, or poly) and the insulator is an oxide -- hence the "metal-oxide"
appellation.
Meta-Stable
A condition where the outputs of a logic function are
oscillating uncontrollably between undefined values.
Micro
Unit qualifier (symbol = u) representing one millionth,
or 10-6. For example, 3uS stands for 3 x 10-6 Seconds.
Microwave
The range in the electromagnetic spectrum from 300
MHz to 30 GHz (with corresponding wavelengths from 100 cm to 1 cm).
Microwire
A trade name for one incarnation of discrete wire technology.
Microwire augments the main attributes of multiwire with laser-drilled
blind vias, allowing these boards to support the maximum number of tracks
and components.
Millman's method
The voltage on the ends of branches in parallel is
equal to the sum of the currents flowing in every branch divided by the
total equivalent conductance.
Minterm
The logical AND of the variables associated with an
input combination to a logical function.
MMIC
Monolithic Microwave Integrated Circuit
Mod or Modulus
Refers to the number of states that a function such
as a counter will pass through before returning to its original value.
For example, a function that counts from 00002 to 11112 has a modulus
of 16 and would be called a modulo-16 or mod-16 counter.
Molecular Beam Epitaxy (MBE)
A technique for creating thin films on substrates in
precise patterns, in which the substrate is placed in a high vacuum,
and a guided beam of ionized molecules is fired at it, effectively allowing
molecular-thin layers to be "painted" onto the substrate where required.
MOS
See Metal-Oxide Semiconductor.
MOSFET
Metal-oxide semiconductor field-effect transistor.
MSI
See Medium-Scale Integration.
Multichip Module (MCM)
A generic name for a group of advanced interconnection
and packaging technologies featuring unpackaged integrated circuits mounted
directly onto a common substrate.
Multilayer
A printed circuit board constructed from a number of
very thin single-sided and/or double-sided boards which are bonded together
using a combination of temperature and pressure.
Multiplexer (digital)
A logic function that uses a binary value, or address,
to select between a number of inputs and conveys the data from the selected
input to the output.
Multiwire
A trade name for one incarnation of discrete wire technology.
Multizone
A stackup that contains zones or areas, each of which contains a subset of the layers in the stackup.
Mutual Capacitance
The capacitance between two conductors (one considered
aggressor, the other victim) when all other conductors are connected
together and then regarded as an ignored ground. It describes the amount
of coupling due to the electric field. The mutual capacitance will inject
an often undesired current into the victim line proportional to the rate
of change of voltage on the aggressor line. Mutual Capacitance it a cause
of crosstalk.
Mutual Inductance
The inductance between two conductors (one considered
aggressor, the other victim) placed close enough that the magnetic field
induced by a current flowing into the aggressor line encompasses the
victim. The mutual inductance will inject an often undesired voltage
noise onto the victim proportional to the rate of change of the current
on the aggressor line.
Glossary: N
Nano
Unit qualifier (symbol = n) representing one thousandth
of one millionth, or 10-9. For example, 3nS stands for 3 x
10-9 Seconds.
Nanobot
A molecular-sized robot (see Nanotechnology below)
Nanophase Materials
A form of matter which was only recently discovered,
in which small clusters of atoms form the building blocks of a larger
structure. These structures differ from those of naturally occurring
crystals, in which individual atoms arrange themselves into a lattice.
Nanotechnology
Nanotechnology is an elusive term that is used by different
research-and-development teams to refer to whatever it is that they're
working on at the time. However, irrespective of their particular area
of interest, nanotechnology always refers to something extremely small.
One of the more exciting branches of nanotechnology that has been suggested
as having potential in the future is that of micro-miniature electronic
products that assemble themselves.
N-channel MOS (NMOS)
Refers to the order in which the semiconductor is doped
in a MOS device. That is, which structures are constructed as N-type
versus P-type material.
Negative-Edge
A transition from a logic 1 to a logic 0. Also known
as a falling edge.
Negative Ion
An atom or group of atoms with an extra electron.
Negative Logic
A convention which dictates the relationship between
logical values and the physical voltages used to represent them. The
more negative potential is considered to represent TRUE and the more
positive potential is considered to represent FALSE. Also known as negative
true logic.
Negative Resist
A process where ultraviolet radiation passing through
the transparent areas of a mask causes the resist to be cured. The uncured
areas are then removed using an appropriate solvent.
Negative Signal Plane
A conducting layer in, or on, a substrate providing
a grounding, or reference, point for components. There may be several
negative signal planes separated by insulating layers.
Negative-True
A convention which dictates the relationship between
logical values and the physical voltages used to represent them. The
more negative potential is considered to represent TRUE and the more
positive potential is considered to represent FALSE. Also known as negative
logic.
Nibble
See Nybble.
NMOS
See N-channel MOS.
Noise Figure / Noise Factor
The Noise Factor of a transducer at a specified input
frequency is the ratio of (a/b) where “a and b” are:
(a) the available Signal to Noise Ratio (SNR)
at the signal generator terminals per unit bandwidth when the temperature
of the input termination (generator or source) is 290 K and the bandwidth
is limited by the transducer, to
(b) the available SNR per unit bandwidth at
the output terminals of the transducer.
Traditionally:
Noise Figure NF = 10 log(noise factor F)
Noise Temperature (Te) = To(F - 1)
Where:
- Te is the noise temperature
- To is standard temperature 290 K
- F is noise factor
Noise Floor
This is defined as the lowest possible input to a chain
or a component, that will produce a detectable output.
Noise Temperature
This is the amount of thermal noise in a chain or a
component. Noise Factor and Noise Temperature (Te) are related as follows:
Noise Temperature (Te) = (F - 1)To
Where:
- Te is the noise temperature
- To is standard temperature 290 K
- F is noise factor
For example, a noise figure of 2.0 dB is equivalent
to a Noise Temperature of 170 K.
Nominal Design
The original model on which Optimetrics analyses are
based.
Non-Volatile
A memory device which does not lose its data when power
is removed from the system.
Non-Volatile RAM
A device which is generally formed from an SRAM die
mounted in a package with a very small battery, or as a mixture of SRAM
and EEPROM cells fabricated on the same die.
Norton's theorem
Any two-terminal collection of voltage sources and
resistors is electrically equivalent to an ideal current source in parallel
with a single resistor.
NPN (N-type - P-type - N-type)
Refers to the order in which the semiconductor is doped
in a bipolar junction transistor.
N-Port
An N-port component is typically characterized by network
parameter data contained in the N-port itself in spreadsheet form or
(more usually) by network parameter data contained in an external file.
N-type
A piece of semiconductor doped with impurities that
make it amenable to donating electrons.
Nybble
A group of four binary digits, or bits (also called
a nibble).
Glossary: O
Octal
Base-8 numbering system. Each octal digit can be directly
mapped onto three binary digits, or bits.
Ohm
Unit of resistance. The Greek letter omega, *, is often
used to represent ohms; for example, 1M* indicates one million ohms.
Ohm's law
The voltage across a resistor is the product of its
resistance and the current flowing through it.
One-Hot Encoding
A form of state assignment for state machines in which
each state is represented by an individual state variable.
One-Time Programmable
A device such as a PAL, PLA, or PROM that can only
be programmed a single time and whose contents cannot be subsequently
erased.
Optical Interconnect
The generic name for interconnection strategies based
on opto-electronic systems, including fiber-optics, free-space, guided-wave,
and holographic techniques.
Optical Lithography
A process in which radiation at optical wavelengths
(usually in the ultraviolet range) is passed through a mask, and the
resulting patterns are projected onto a layer of resist coating the substrate
material.
Optical Mask
A sheet of material carrying patterns that are either
transparent or opaque to the wavelengths used in an optical-lithographic
process. Such a mask can carry hundreds of thousands of fine lines and
geometric shapes.
Opto-Electronic
Refers to a system which combines optical and electronic
components.
Organic Resist
A material which is used to coat a substrate and is
then selectively cured to form an impervious layer. These materials are
called organic because they are based on carbon compounds as are living
creatures.
Organic Solvent
A solvent for organic materials such as those used
to form organic resists.
Organic Substrate
Substrate materials such as FR4, in which woven glass
fibers are bonded together with an epoxy. These materials are called
organic because epoxies are based on carbon compounds as are living creatures.
Overglassing
One of the final stages in the integrated circuit fabrication
process in which the entire surface of the wafer is coated with a layer
of silicon dioxide or silicon nitride. This layer may also be referred
to as the barrier layer or the passivation layer. An additional lithographic
step is required to pattern holes in this layer to allow connections
to be made to the pads.
Glossary: P
Package
Leaded assembly (inside of which one or more dies are
mounted and connected) for use in larger circuits.
Pad
An area of metallization on a substrate used for probing
or to connect to a via, plated through-hole, or an external interconnect.
Pad Grid Array (PGA)
A packaging technology in which a device's external
connections are arranged as an array of conducting pads on the base of
the package.
Padstack
Refers to any pads, anti-pads, and thermal relief pads
associated with a via or a plated through-hole as it passes through the
layers forming the substrate.
Padcap
A special flavor of circuit board used for high-reliability
military applications. Distinguished by the fact that the outer surfaces
of the board have pads but no tracks. Signal layers are only created
on the inner planes, and tracks are connected to the surface pads by
vias.
Parallel-In Serial-Out (PISO)
Refers to a shift register in which the data is loaded
in parallel and read out serially.
Parasitic Effects
The effects caused by undesired resistance, capacitance,
or inductance inherent in the material or topology of a track or component.
Passive Trimming
A process in which a laser beam is used to trim components
such as thick-film and thin-film resistors on an otherwise unpopulated
and unpowered hybrid or multichip module substrate. Probes are placed
at each end of a component to monitor its value while the laser evaporates
some of the material forming the component.
Pass-Transistor Logic
A technique for connecting MOS transistors such that
data signals pass between their source and drain terminals. Pass-transistor
logic minimizes the number of transistors required to implement a function,
and is typically employed by designers of cell libraries or full-custom
integrated circuits.
PGA
See either Pad Grid Array or Pin Grid Array.
Photo-Transistor
A special transistor which converts an optical input
in the form of light into an equivalent electronic signal in the form
of a voltage or current.
Pico
Unit qualifier (symbol = p) representing one millionth
of one millionth, or 10-12. For example, 3pS stands for 3
x 10-12 Seconds.
PIN Diode
A diode where a thin layer exists between the N and
P regions. Rectification with pin diodes is limited. They actually behave
more like a variable resistor that changes based upon the DC bias.
Pin Grid Array (PGA)
A packaging technology in which a device's external
connections are arranged as an array of conducting leads, or pins, on
the base of the package.
PISO
See Parallel-In Serial-Out.
Place-Value
Refers to a numbering system in which the value of
a particular digit depends both on the digit itself and its position
in the number.
PlasmA gaseous state in which the atoms or molecules
are dissociated to form ions.
Plated Through-Hole (PTH)
(1) A hole in a double-sided or multilayer board that
is used to accommodate a through-hole component lead and is plated with
copper.
(2) An alternative name for the lead through-hole technique for
populating circuit boards in which component leads are inserted into
plated through-holes.
PMOS (P-channel MOS)
Refers to the order in which the semiconductor is doped
in a MOS device. That is, which structures are constructed as P-type
versus N-type material.
PNP (P-type - N-type - P-type)
Refers to the order in which the semiconductor is doped
in a bipolar junction transistor.
Polysilicon Layer
An internal layer in an integrated circuit used to
create the gate electrodes of MOS transistors. In addition to forming
gate electrodes, the polysilicon layer can also be used to interconnect
components. There may be several polysilicon layers separated by dielectric
(insulating) layers.
Populating
The act of attaching components to a substrate.
Positive Logic
A convention which dictates the relationship between
logical values and the physical voltages used to represent them. The
more positive potential is considered to represent TRUE and the more
negative potential is considered to represent FALSE. Also known as positive
true logic.
Positive Resist
A process where radiation passing through the transparent
areas of a mask causes previously cured resist to be degraded. The degraded
areas are then removed using an appropriate solvent.
Positive-Edge
A transition from a logic 0 to a logic 1. Also known
as a rising edge.
Positive-True
A convention which dictates the relationship between
logical values and the physical voltages used to represent them. The
more positive potential is considered to represent TRUE and the more
negative potential is considered to represent FALSE. Also known as positive
logic.
Power Amplifier
A class of amplifier with the primary purpose of delivering
high output power (usually accompanied by significant dissipated power).
Power Plane
A conducting layer in or on the substrate providing
power to the components. There may be several power planes separated
by insulating layers.
Prepreg
Non-conducting semi-cured layers of FR4 used to separate
conducting layers in a multilayer circuit board.
Primitives
Simple logic functions such as BUF, NOT, AND, NAND,
OR, NOR, XOR, and XNOR may be referred to as primitive logic gates or
primitives.
Product Term
A set of literals linked by an AND operator.
Programmable Array Logic (PAL)
A programmable logic device in which the AND array
is programmable but the OR array is pre-defined.
Programmable Logic Array (PLA)
The most user-configurable of the traditional programmable
logic devices, because both the AND and OR arrays are programmable.
Programmable Logic Device (PLD)
The generic name for a device constructed in such a
way that the designer can configure, or "program" it to perform a specific
function.
Programmable Read-Only Memory (PROM)
A programmable logic device in which the OR array is
programmable but the AND array is pre-defined. Usually considered to
be a memory device whose contents can be electrically programmed (once)
by the designer.
Project
A container that groups designs and their associated
settings, including report definitions, in a file with a .adsn extension.
To the fullest extent possible, projects are portable in that they include,
rather than merely refer to, the library elements (graphical symbols,
materials, footprints, and so on) of the components and models they contain.
Multiple projects can be open simultaneously.
PROM
See Programmable Read-Only Memory.
Pseudo-Random
An artificial sequence of values that give the appearance
of being random.
PTH
See Plated Through-Hole.
P-type
A piece of semiconductor doped with impurities that
make it amenable to accepting electrons.
Pulling
The difference between the maximum frequency of a VCO
when the phase angle of the load impedance reflection coefficient varies
through 360 degrees.
Pulsed Radar
A transmit and receive system used for ranging and
detection that transmits a train of short bursts of high microwave signals
and receives return signals reflected from a target.
Pushing
The change in frequency when the supply voltage changes,
expressed in MHz/V.
Glossary: Q
Q
Quality factor; a measure of stored energy/dissipated
energy. Also a measure of bandwidth.
QAM
Quadrature amplitude modulation.
QFP
See Quad Flat Pack.
QPSK
Quadrature phase-shift keying.
Quad Flat Pack (QFP)
The most commonly used package in surface mount technology
to achieve a high lead count in a small area. Leads are presented on
all four sides of a thin square package.
Quinary
Base-5 numbering system.
Glossary: R
Radio Frequency (RF)
The range in the electromagnetic spectrum
loosely defined from 30 MHz to 3 GHz (with corresponding wavelengths
from 1000 cm to 10 cm).
Radix
Refers to the number of digits in a numbering system.
For example, the decimal numbering system is said to be radix-10. May
also be referred to as the "base".
Rats Layer
A non-physical, default layer in the stackup that displays a drawing of logical connections between different components, circuit elements, and net connections. A single connection is called a rat and all of the connections on a rat layers is a rat's nest.
Reed-Müller Logic
Logic functions implemented using only XOR and XNOR
gates.
Refractory Metal
Metals such as tungsten, titanium, and molybdenum which
are capable of withstanding extremely high, or refractory, temperatures.
Remotely Reconfigurable Hardware
A product whose function may be customized remotely,
by telephone or radio, while remaining resident in the system (see also
Configurable Hardware, Reconfigurable Hardware, Dynamically Reconfigurable
Hardware, and Virtual Hardware).
Reflection
The appearance of a previously transmitted signal on
the transmission line causing interference with the current signal. Reflections
are caused by a poorly terminated or discontinuous transmission line,
where the signal energy is not fully absorbed within the receiver and
is therefore transmitted back toward the transmitter.
Resist
A material which is used to coat the substrate and
is then selectively cured to form an impervious layer.
Resistor-Transistor Logic (RTL)
Logic gates implemented using particular configurations
of resistors and bipolar junction transistors. For the majority of today's
designers, resistor-transistor logic is of historical interest only.
Return Loss
Return Loss (dB) is defined as a ratio of the incoming
signal to the same reflected signal as it enters a component.
Return Loss (dB) = 10 * LOG10(Reflected Power/Incident
Power)
RF
See Radio Frequency.
RF Power
A class of engineering. Circuits and signals primarily
concerned with power levels ranging from a few watts to tens of thousands
of watts in the RF spectrum.
RF Power Transmitter
A discrete packaged transistor used in the amplification
of RF power.
Rigid Flex
Hybrid constructions which combine standard rigid circuit
boards with flexible printed circuits, thereby reducing the component
count, weight, and susceptibility to vibration of the circuit, and greatly
increasing its reliability.
Ringing
Common name for the waveform that is seen when a transmission
line ends at a high impedance discontinuity. The signal first overshoots,
then dips down below the target value, and continues this with decreasing
amplitude until it converges on the target voltage.
Risetime
The time it takes for a signal to rise from 10% of
its total logic swing to 90% of its total logic swing.
Rising-Edge
A transition from a logic 0 to a logic 1. Also known
as a positive edge.
RTL
See Resistor-Transistor Logic.
Glossary: S
Sample Rate
Time increment of analysis. Sometimes referred to as
sampling rate.
Sampling
The process of converting an analog signal into a series
of digital values.
Scalar Notation
A notation in which each signal is assigned a unique
name; for example, a3, a2, a1, and a0.
Scaling
A technique for making transistors switch faster by
reducing their size. This strategy is known as scaling, because all of
the transistors features are typically reduced by the same proportion.
Schematic
Common name for a circuit diagram.
Scrubbing
The process of vibrating two pieces of metal, or metal
coated materials, at ultrasonic frequencies to create a friction weld.
Seed Value
An initial value loaded into a linear feedback shift
register or random number generator.
Sensor
A transducer that detects a physical quantity and converts
it into a form suitable for processing. For example, a microphone is
a sensor which detects sound and converts it into a corresponding voltage
or current.
Sequential
A function whose output value depends not only on its
current input values, but also on previous input values. That is, the
output value depends on a sequence of input values.
Side-Emitting Laser Diode
A laser diode constricted at the edge of an integrated
circuit's substrate such that, when power is applied, the resulting laser
beam is emitted horizontally; that is, parallel to the surface of the
substrate.
Sign Bit
The most significant binary digit, or bit, of a signed
binary number. If set to a logic 1, this bit represents a negative quantity.
Signal Conditioning
Amplifying, filtering, or otherwise processing a signal.
Signal Layer
A layer carrying tracks in a circuit board, hybrid,
or multichip module. See also wiring layer.
Signature
Refers to the checksum value from a cyclic-redundancy-check
when used in the guided-probe form of functional test.
Signature Analysis
A guided-probe functional-test technique based on signatures.
Signed Binary Number
A binary number in which the most-significant bit is
used to represent a negative quantity. Thus, a signed binary number can
be used to represent both positive and negative values.
Sign-Magnitude
Negative numbers in standard arithmetic are typically
represented in sign-magnitude form by prefixing the value with a minus
sign; for example, -27. For reasons of efficiency, computers rarely employ
the sign-magnitude form. Instead, they use signed binary numbers to represent
negative values.
Silicon Bumping
The process of depositing additional metallization
on a die's pads to raise them fractionally above the level of the Barrier
Layer.
Silicon Chip
Although a variety of semiconductor materials are available,
the most commonly used is silicon and integrated circuits are popularly
known as silicon chips, or simply chips.
Silicon Compiler
The program used in compiled cell technology to generate
the masks used to create components and interconnections. May also be
used to create data-path functions and memory functions.
Single-Sided
A printed circuit board with tracks on only one side.
Sintering
A process in which ultra-fine metal powders weld together
at temperatures much lower than those required for larger pieces of the
same materials.
SIPO (Serial-In Parallel-Out)
Refers to a shift register in which the data is loaded
in serially and read out in parallel.
SISO (Serial-In Serial-Out)
Refers to a shift register in which the data is both
loaded in and read out serially.
Skew
Time delay between different bits transmitted at the
same time, measured at the receiver.
Skin Effect
In the case of high frequency signals, electrons are
only conducted on the outer surface, or skin, of a conductor. This phenomenon
is known as the skin effect.
Small-Scale Integration (SSI)
Refers to the number of logic gates in a device. By
one convention, small-scale integration represents a device containing
1 to 12 gates.
SMD
See Surface Mount Device.
SMOBC
See Solder Mask Over Bare Copper.
SMT
See Surface Mount Technology.
SNR
Signal-to-noise ratio.
Soft Macro (Macro Function)
A logic function defined by the manufacturer of an
application-specific integrated circuit. The function is described in
terms of the simple functions provided in the cell library and connections
between them. The assignment of cells to basic cells and the routing
of the tracks is determined at the same time, and using the same tools,
as for the other cells specified by the designer.
Solder Bumping
A flipped chip technique in which spheres of solder
are formed on the die's pads. The die is flipped and the solder bumps
are brought into contact with corresponding pads on the substrate. When
all the chips have been mounted on the substrate, the solder bumps are
melted using reflow soldering or vapor-phase soldering.
Solder Mask
A layer applied to the surface of the substrate that
prevents solder from sticking to any metallization except where holes
are patterned into the mask.
Solder Mask Over Bare Copper (SMOBC)
A technique in which the solder mask is applied in
advance of the tin-lead plating. This results in lighter circuit boards
because the tin-lead alloy is only used to plate the pads.
Solution
A solution is the successful result of an analysis,
or imported results available for plotting.
Space
Used to refer to the width of the gap between adjacent
tracks.
SPICE
Simulated Program for Integrated Circuit Emulation
SRAM
See Static RAM.
SS-CDMA
Spread-spectrum code-division multiple access.
SSI
See Small-Scale Integration.
Stackup
An arrangement of physical signal and dielectric layers that is used in the design of circuit boards. In Circuit, the stackup editor lists conceptual non-stackup layers with the physical stackup layers.
Standard Cell
An application-specific integrated circuit which, unlike
a gate array, does not use the concept of a basic cell and does not have
any pre-fabricated components. The manufacturer creates custom masks
for every stage of the device's fabrication allowing each logic function
to be created using the minimum number of transistors.
State Assignment
The process by which the states in a state machine
are assigned to the binary patterns that are to be stored in the state
variables.
State Diagram
A graphical representation of the operation of a state
machine.
State Machine
The actual implementation (in hardware or software)
of a function that can be considered to consist of a set of states through
which it sequences.
State Table
A tabular representation of the operation of a state
machine. Similar to a truth table, but also includes the current state
as an input and the next state as an output.
State Transition
An arc connecting two states in a state diagram.
State Variable
One of a set of registers whose values represent the
current state occupied by a state Static Flex.
Statement
A sentence that asserts or denies an attribute about
an object or group of objects.
Static Flex
A type of flexible printed circuit which can be manipulated
into permanent three-dimensional shapes for applications such as calculators
and high-tech cameras which require efficient use of volume and not just
area.
Static RAM (SRAM)
A memory device in which each cell is formed from four
or six transistors configured as a latch or a flip-flop. The term static
is used because, once a value has been loaded into an SRAM cell, it will
remain unchanged until it is explicitly altered or until power is removed
from the device.
Steady State
A condition in which nothing is changing or happening.
Subatomic Erosion
A process in which structures on an integrated circuit's
substrate are eroded by the flow of electrons in much the same way as
land is eroded by a river (also known as electromigration)
Substrate
Generic name for the base layer of an integrated circuit,
hybrid, multichip module, or circuit board. Substrates may be formed
from a wide variety of materials, including semiconductors, ceramics,
FR4 (fiberglass), glass, sapphire, or diamond depending on the application.
Note that the term substrate has traditionally not been widely used in
the circuit board world, at least not by the people who manufacture the
boards. However, there is an increasing tendency to refer to a circuit
board as a substrate by the people who populate the boards. The main
reason for this is that circuit boards are often used as substrates in
hybrids and multichip modules, and there is a trend toward a standard
terminology across all forms of interconnection technology.
Subtractive Process
A process in which a substrate is first covered with
conducting material, then any unwanted material is subsequently removed,
or subtracted.
Superconductor
A material with zero resistance to the flow of electric
current.
Surface Mount Device (SMD)
A component whose packaging is designed for use with
surface mount technology.
Surface Mount Technology (SMT)
A technique for populating hybrids, multichip modules,
and circuit boards, in which packaged components are mounted directly
onto the surface of the substrate. A layer of solder paste is screen
printed onto the pads and the components are attached by pushing their
leads into the paste. When all of the components have been attached,
the solder paste is melted using either reflow soldering or vapor-phase
soldering.
Surface-Emitting Laser Diode
A laser diode constricted on an integrated circuit's
substrate such that, when power is applied, the resulting laser beam
is emitted directly away from the surface of the substrate.
Sweep Definition
Also called variable sweep definition. A set
of variable values within a range that Optimetrics drives the Electronics Desktop
to solve when a parametric setup is analyzed. A parametric setup can
include one or more sweep definitions.
Synchronous
(1)A signal whose data is not acknowledged or acted
upon until the next active edge of a clock signal. (2)A system whose
operation is synchronized by a clock signal.
System Gain
The net loss of a system as a measure of reliability with respect to system parameters. It measures the difference between the output power and minimum input power required for satisfactory performance. It represents a system net loss, and is represented as a negative dB value that is larger than or equal to the summed gains and losses of a signal propagating in a system from transmitter to receiver.
Glossary: T
Tap
A register output which is used to generate the next
data input to a linear feedback shift register.
Tape Automated Bonding (TAB)
A process in which transparent flexible tape has tracks
created on its surface. The pads on unpackaged integrated circuits are
attached to corresponding pads on the tape which is then stored in a
reel. Silver-loaded epoxy is screen printed on the substrate at the site
where the device is to be located and onto the pads to which the device's
leads are to be connected. The reel of TAB tape is fed through an automatic
machine which pushes the device and the TAB leads into the epoxy. When
the silver-loaded epoxy is cured using reflow soldering or vapor-phase
soldering, it forms electrical connections between the TAB leads and
the pads on the substrate.
TDM
Time-division multiplexing.
TDMA
Time-division multiple access.
Technology File
A technology file is a collection of information, specifiable
by name at design-creation time using the Choose Layout Technology dialog
box, that specifies material stackup properties for layout, substrates
for simulation, and component libraries for design creation. A technology
(.asty) file may be saved from the current project via the File menu.
A technology file initializes a design with a set of data to avoid repeated
entry of commonly used data. This data can consist of layers and stackup
information for layout, configured libraries of components, and substrate
definition(s) for circuit analysis. Users and foundries can customize
Technology files for their own manufacturing process and simulation models.
Tertiary Logic
An experimental technology in which logic gates are
based on three distinct voltage levels. The three voltages are used to
represent the tertiary digits 0, 1, and 2, and their logical equivalents
FALSE, TRUE, and MAYBE.
Thermal Impedance
Relates the temperature rise for a given dissipated
power (which employs an analogy to the voltage-current relationship of
impedance).
Thermal Relief Pad
A special pattern etched around a via or a plated through-hole
to connect it into a power or ground plane. A thermal relief pad is necessary
to prevent too much heat being absorbed into the power or ground plane
when the board is being soldered.
Thermal Tracking
Typically used to refer to the problems associated
with optical interconnection systems whose alignment may be disturbed
by changes in temperature.
Thevenin's theorem
Any two-terminal combination of voltage sources and
resistors is electrically equivalent to a single voltage source in series
with a single resistor.
Thick-Film Process
A process used in the manufacture of hybrids and, to
a lesser extent, multichip modules in which signal and dielectric (insulating)
layers are screen-printed onto the substrate.
Thin-Film Process
A process used in the manufacture of hybrids and multichip
modules in which signal layers and dielectric (insulating) layers are
created using opto-lithographic techniques.
Time-Of-Flight
The time taken for a signal to propagate from one logic
gate or opto-electronic component to another.
Tin-Lead Plating
An electroless plating process in which exposed areas
of copper on a circuit board are coated with a layer of tin-lead alloy.
The alloy is used to prevent the copper from oxidizing and provides protection
against contamination.
Tinning
An abbreviation of tin-lead plating, which is an electroless
plating process in which exposed areas of copper on a circuit board are
coated with a layer of tin-lead alloy. The alloy is used to prevent the
copper from oxidizing and provides protection against contamination.
Toggle
Refers to the contents or outputs of a logic function
switching to the inverse of their previous logic values.
TOI
Third-order intercept point.
Total Voltage
Total voltage = Incident voltage + reflected voltage, that is VT = Va + Vb.
Trace
A conducting connection between electronic components.
May also be called a track or a signal. In the case of integrated circuits,
such interconnections are often referred to collectively as metallization.
Tracks
A conducting connection between electronic components.
May also be called a trace or a signal. In the case of integrated circuits,
such interconnections are often referred to collectively as metallization.
Transducer
A device that converts input energy of one form into
output energy of another.
Transistor
A three-terminal semiconductor device that, in the
digital world, can be considered to operate like a switch.
Tri-State Function
A function whose output can adopt three states: 0,
1, and Z (high-impedance) The function does not drive any value in the
Z state and, in many respects, may be considered to be disconnected from
the rest of the circuit.
Truth Table
A convenient way to represent the operation of a digital
circuit as columns of input values and their corresponding output responses.
TTL (Transistor-Transistor Logic)
Logic gates implemented using particular configurations
of bipolar junction transistors.
Glossary: U
ULA
See Uncommitted Logic Array.
Ultra-Large-Scale Integration (ULSI)
Refers to the number of logic gates in a device. By
one convention, ultra-large-scale integration represents a device containing
a million or more gates.
ULSI
See Ultra-Large-Scale Integration.
Uncommitted Logic Array (ULA)
One of the original names used to refer to gate array
devices. This term has largely fallen into disuse.
Unsigned Binary Number
A binary number in which all the bits are used to represent
positive quantities. Thus, an unsigned binary number can only be used
to represent positive values.
Undershoot
The percentage a waveform falls below its lowest determined
value before setting at the correct value.
Glossary: V
Vapor-Phase Soldering
A surface mount process in which a substrate carrying
components attached by solder paste is lowered into the vapor-cloud of
a tank containing boiling hydrocarbons. This melts the solder paste thereby
forming good electrical connections. However, vapor-phase soldering is
becoming increasingly less popular due to environmental concerns.
Vaporware
Refers to either hardware or software that exist only
in the minds of the people who are trying to sell them to you.
Variable Sweep Definition
Also called sweep definition. A set of variable
values within a range that Optimetrics drives HFSS or Q3D to solve when
a parametric setup is analyzed. A parametric setup can include one or
more sweep definitions.
Vector Notation
A notation used in logic simulation and synthesis in
which a single name is used to reference a group of signals, and individual
signals within the group are referenced by means of an index; for example,
a[3:0] = a[3], a[2], a[1], and a[0].
Very-Large-Scale Integration (VLSI)
Refers to the number of logic gates in a device. By
one convention, very-large-scale integration represents a device containing
1,000 to 999,999 gates.
Via
A hole filled or lined with a conducting material which
is used to link two or more conducting layers in a substrate.
Virtual Hardware or Virtual Logic
An extension of dynamically configurable hardware based
on a new generation of FPGAs which were introduced around the beginning
of 1994. In addition to supporting the dynamic reconfiguration of selected
portions of the internal logic, these devices also feature: no disruption
to the device's inputs and outputs; no disruption to the system-level
clocking; the continued operation of any portions of the device that
are not undergoing reconfiguration; and no disruption to the contents
of internal registers during reconfiguration, even in the area being
reconfigured (see also Configurable Hardware, Reconfigurable Hardware,
Remotely Reconfigurable Hardware, and Dynamically Reconfigurable Hardware).
Virtual Memory
A trick used by a computer's operating system to pretend
that it has access to more memory than is actually available. For example,
a program running on the computer may require ten mega-bytes to store
its data, but the computer may have only five mega-bytes of memory available.
To get around this problem, whenever the program attempts to access a
memory location that does not physically exist, the operating system
performs a slight-of-hand and exchanges some of the contents in the memory
with data on the hard disk.
VLSI
See Very-Large-Scale Integration.
Volatile
Refers to a memory device which loses any data it contains
when power is removed from the system; for example, random-access memory
in the form of SRAM or DRAM
Glossary: W
Wafer Probing
The process of testing individual integrated circuits
while they still form part of a wafer. An automated tester places probes
on the device's pads, applies power to the power pads, injects a series
of signals into the input pads, and monitors the corresponding signals
returned from the output pads.
Wave Soldering
A process used to solder circuit boards populated with
through-hole components. A wave generating mechanism maintains a wave
of hot, liquid solder traveling back and forth across the surface of
a tank. The populated circuit boards are passed over the wave soldering
machine on a conveyor belt. The velocity of the convener belt is carefully
controlled and synchronized such that the solder wave brushes across
the bottom of the board only once.
Waveguide
A transparent path bounded by non-transparent, reflective
areas, which is fabricated directly onto the surface of a substrate.
Used in the optical interconnection strategy known as guided-wave.
W-CDMA
Wideband code-division multiple access. Typically defined
with 5 MHz channels and 3.84 MHz carrier signals.
Wire Bonding
The process of connecting the pads on an unpackaged
integrated circuit to corresponding pads on a substrate using wires that
are finer than a human hair. Wire bonding may also be used to connect
the pads on an unpackaged integrated circuit, hybrid, or multichip module
to the leads of the component package.
Wiring Layer
A layer carrying wires in a discrete wired board. See
also signal layer.
Word
A group of signals or logic functions performing a
common task and carrying or storing similar data; for example, a value
on the data bus could be referred to as a data word.
Glossary: X
X-Ray Lithography
Similar in principle to optical lithography, but capable
of constructing much finer features due to the shorter wavelengths involved.
However, X-ray lithography requires an intense source of X-rays, is more
difficult to use, and is considerably more expensive than optical lithography.
Glossary: Y
Yield
The number of devices that work as planned, specified
as a percentage of the total number actually fabricated.
Glossary: Z
Zepto (z)
The symbol used to represent the high-impedance
state in tri-state logic.
Zone
A spatial area on a printed circuit board that may contain a subset or all of the layers in the board’s stackup.
