Digital CMOS Abbreviation P Alphabet Dictionary
P-type silicon is silicon in which the acceptor concentration (for holes) is higher than the donor concentration (for electrons). This results in the majority of charge carriers being holes. When p-type silicon is depleted, it forms space-charge regions with negative ions.
In VHDL, a package is a construct that contains constants, components, types, subtypes, attributes, functions, and procedures. It allows these items to be shared and reused across multiple files, promoting modularity and maintainability of VHDL designs.
Package (IC Packaging)
In the context of integrated circuits (ICs), a package refers to the external housing of a semiconductor die. It typically consists of a substrate and a protective top layer, often made of plastic or ceramic. The die is mounted and connected to the substrate, and bonding pads on the die connect to the package pins. The package provides mechanical support, protection, and cooling for the die.
A pad, in the context of semiconductor devices, is a large metal rectangle located at the top or periphery of a die. It is exposed through the overglass layer and serves as a point of contact for external pins to communicate with the core of the die. Wires in the packaging facility connect pins to these pads, allowing communication with the die’s core through pad interface circuitry.
Pad Guard Ring
A pad guard ring is a diffusion ring surrounding a pad interface. This diffusion ring is made of the opposite type of semiconductor material compared to the substrate. It is connected to a potential that creates a reverse-biased PN junction. Pad guard rings serve multiple purposes, including protection against latch-up caused by voltage fluctuations on the pin and isolation from noise.
A pad interface is an interface circuit used for signal conditioning as signals move between the die core and bonding pads, or vice versa depending on the pin type. This interface includes features such as electrostatic discharge (ESD) protection, buffering, and level conversion.
Parallel Prefix Adder
Parallel prefix adders are specialized adder circuits designed for high-speed addition. They prioritize speed over area efficiency and utilize large-scale parallelism and gradual calculations of group generates and propagates to resolve bit positions efficiently.
Parametric testing is a type of testing that assesses specific parameters of a circuit’s performance, such as operating frequency, power dissipation, or temperature range. It goes beyond functional testing, which only checks if a circuit produces expected results.
In binary long multiplication, a partial product is the result of multiplying one bit from the multiplier by one bit from the multiplicand. The partial product is a simple AND gate operation, resulting in either a null value or a copy of the multiplicand bit.
Partitioning is the process of dividing a complex design into smaller, manageable partitions or blocks. This typically occurs after synthesis and is a designer-led process. Effective partitioning involves grouping related and functionally significant units together to facilitate design management.
Pauli’s Exclusion Principle
Pauli’s Exclusion Principle is a fundamental principle in quantum mechanics. It states that no two electrons within an atom can occupy the same quantum state simultaneously if they have the same spin. This principle helps explain the structure of electron energy levels.
A phonon is a quantum of vibrational energy associated with crystal lattice vibrations in a solid material. It is the quantum mechanical counterpart of sound waves in a crystal lattice.
Photolithography is a key process in ASIC fabrication. It uses light to project and create patterns on a photosensitive material called photoresist. These patterns guide subsequent processes for introducing materials onto the semiconductor wafer.
A photomask is a mask used in photolithography. It is made of a transparent glass substrate with an opaque metallic pattern. Photomasks are used to project patterns onto the semiconductor wafer during photolithography, defining the layout of integrated circuits.
The photoresist is a photosensitive material applied to a semiconductor wafer during photolithography. It undergoes chemical changes when exposed to light, making it either soluble (positive photoresist) or insoluble (negative photoresist) in a specific development solvent. Photoresist plays a critical role in transferring patterns from photomasks to wafers during fabrication.
A pin is a physical port on a packaged microchip, typically made of metal (e.g., gold or copper). Pins enable external communication with the chip through printed circuit boards (PCBs) or mounting hardware. Pins can be designated as inputs, outputs, or bidirectional, depending on their functions.
Pin Grid Array
Pin Grid Array (PGA) is a type of integrated circuit (IC) package design in which the pins are located on the bottom of the IC rather than its perimeter. This arrangement allows for a significant increase in the number of pins, which can enhance the chip’s connectivity. PGA chips require special mounting platforms to facilitate the connection of the bottom pins.
Pinch-off refers to a process in a field-effect transistor (FET) where the channel, which allows current flow between the source and drain terminals, narrows and eventually closes near the drain terminal. This occurs when the drain potential is sufficiently high and prevents the gate-to-drain voltage from exceeding the FET’s threshold voltage. Pinch-off is associated with FET saturation.
A pipeline is a circuit design composed of combinational logic blocks separated by registers. In synchronous pipelines, all registers are clocked by the same clock signal. Pipelining is commonly used to increase the throughput of digital circuits and is prevalent in various digital systems.
Placement is the process of positioning standard cells (in application-specific integrated circuits or ASICs) or configurations (in field-programmable gate arrays or FPGAs) within specific locations on a chip. It plays a crucial role in optimizing the physical layout of a digital design.
Placement and Routing
Placement and routing is a dual iterative process used in ASIC and FPGA design. It involves constrained optimization to meet speed and/or area constraints. During placement, standard cells are placed within a defined area, and the routing tool attempts to create interconnections while adhering to the constraints. The process may iterate until closure (meeting the constraints) is achieved.
PMOS (P-channel Metal-Oxide-Semiconductor) is a type of MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) where the body is n-type, and the source and drain are p-type. In PMOS, the majority charge carriers are holes, and it is commonly used for implementing a strong logic “1” in digital circuits.
PN Neutral Zones
PN neutral zones are regions within a PN junction that are situated away from the interface. In these zones, electrical neutrality is restored, meaning the concentration of electrons and acceptor ions balances the concentration of holes and donor ions.
PNP is a type of bipolar junction transistor (BJT) where the collector and emitter regions are p-type, and the base region is n-type. PNP transistors operate based on the flow of holes as the majority of charge carriers. They are less commonly used than their NPN counterparts due to their characteristics.
A poly mask is a photomask used in semiconductor fabrication to define features made of polysilicon. This includes elements such as MOSFET gates and polysilicon wires. The intersection of a poly mask and an active mask defines transistor regions.
Polysilicon, also known as polycrystalline silicon, is silicon material with a crystalline structure composed of medium-sized domains. Polysilicon has intermediate electrical and mechanical properties compared to single-crystal silicon. It can be manufactured at lower temperatures and is used for various purposes in semiconductor manufacturing.
In VHDL (VHSIC Hardware Description Language), a port is part of the entity declaration that specifies the inputs and outputs of a digital circuit. Ports include information about direction (input, output, or bidirectional), name, type, and size. They define the interface between the circuit and its environment.
Port Map (VHDL)
In VHDL, a port map is used within a component instance to specify how the ports of that instance are connected to signals in the calling entity. It establishes the interconnections between components in a hierarchical design.
Positive Edge-Triggered Register
A positive edge-triggered register is a type of flip-flop or latch that transfers data from its input to its output on the rising edge (positive edge) of the clock signal. It typically consists of an active-low master latch followed by an active-high slave latch.
A positive skew is a timing skew that occurs when the clock and data signals are distributed in the same direction. It can affect the hold-time conditions in digital circuits but may alleviate setup-time conditions.
Post Extraction Simulation
Post-extraction simulation is a type of simulation performed on a digital circuit after parasitic extraction. It involves back-annotating delay information from parasitic components to the post-place-and-route simulation. This simulation provides a highly accurate representation of circuit behavior, accounting for gate delays, routing delays, and parasitic effects.
Post-place and Route Simulation
Post-place and route simulation is a type of simulation performed on the netlist of a digital circuit after the placement and routing stages in the design process. It includes all the information from the post-synthesis simulation, making it cycle-accurate and bit-accurate. Additionally, it incorporates modeling for routing delays, allowing designers to assess the impact of physical routing on circuit performance.
Post-synthesis simulation is a simulation performed on the netlist generated after the synthesis stage in digital circuit design. It inherits information from behavioral simulation, making it cycle-accurate and bit-accurate. Moreover, it includes data about gate delays obtained from the library, enabling designers to evaluate the expected performance of the synthesized design.
Power Delay Product
The power delay product is a metric used to measure the energy efficiency of a digital circuit. It is calculated by multiplying the power consumption of the circuit by the delay required to produce a single output from that circuit. This metric is expressed in Joules and provides insight into how efficiently a circuit balances power consumption with throughput.
Power density is a measure of power consumption per unit area on a semiconductor chip. It quantifies the distribution of power dissipation, primarily due to resistors, across the chip’s surface area. High power density can lead to increased heating, making effective chip cooling crucial, especially as technology scales.
Power-On Self-Test (POST) is a category of built-in self-tests (BISTs) that automatically run when a digital circuit is powered on. These tests check the status and functionality of the circuit’s components and report any detected problems or faults. POST helps ensure that a circuit operates correctly upon power-up.
In dynamic CMOS logic gates, the precharge phase is one of the clock phases. During this phase, the output node is charged to a known value through a low-impedance path. Logic operations are not performed during the precharge phase, but it is necessary to set up the gate for subsequent logic evaluation.
The predecoder is a part of the row decoder in a memory array. It prepares small product terms, which are then combined using a final AND gate to generate the word-line signal. The predecoder’s purpose is to reduce the complexity of the row decoder, allowing for efficient scaling of memory arrays.
Printed Circuit Board (PCB)
A printed circuit board is an insulating substrate used to assemble and interconnect electrical and electronic components. It features copper tracks or traces etched onto the board’s surface to facilitate electrical connections. PCBs are widely used in electronic devices and systems.
In VHDL (VHSIC Hardware Description Language), a procedure is a subprogram that can contain signal declarations and assignments. Procedures do not have return values but can have multiple arguments with defined directions (similar to ports). They provide a way to encapsulate reusable sequential code.
A process in VHDL is a code section that defines all contained statements as sequential statements. Processes are essential for implementing sequential circuits and can also be used to model combinational circuits. They offer flexibility in coding and control flow.
In the context of binary long multiplication, the product refers to the result of the multiplication operation. It is the outcome of adding all the partial products generated during the multiplication process. The size of the product is determined by the sum of the sizes of the multiplier and multiplicand.
Programming in the context of nonvolatile memories (NVMs) involves changing the state of a memory cell by altering the state of its cell transistor. This is typically achieved by introducing charge into a floating gate using various mechanisms such as avalanche breakdown, hot carrier effect, or Fowler-Nordheim tunneling. Programming time is the duration required to complete this operation.
Programming File (FPGA)
A programming file in FPGA (Field-Programmable Gate Array) design contains the information necessary to reconfigure the logic cells and routing channels within the FPGA. It serves as the final output of the FPGA design flow and enables the FPGA to perform specific functions or tasks.
Projection exposure is an exposure mechanism used in semiconductor lithography. It involves separating the photomask and the wafer using a system of lenses to focus light on the wafer surface. This method reduces optical artifacts and shadows compared to proximity projection. Projection exposure requires the use of a stepper and allows for larger features on the photomask relative to the wafer.
In the context of adders, “propagate” refers to a state in a full adder where the carry-out (C-out) is identical to the carry-in (C-in). This means that the carry logic can be bypassed for that specific bit position. The propagate state can be deduced solely from the operands, allowing for parallel calculation of propagates for all bit positions. Together with “generate,” propagate is a method for conceptualizing the behavior of a full adder, enabling the design of fast adders.
Propagation delay is the time it takes for a signal to travel through a logic gate. It is typically measured as the time difference between the 50% points on the input and output signals of the gate. There are two types of propagation delay: “high to low” (when the output transitions from high to low) and “low to high” (when the output transitions from low to high).
Proximity exposure is an exposure mechanism used in semiconductor lithography. It involves bringing the photomask very close to the wafer but without direct contact with the photoresist. While it protects the mask from damage, proximity exposure can result in significant optical artifacts, often requiring guide features on the photomask.
Pseudo NMOS Logic
Pseudo NMOS logic is a type of ratioed logic family where NMOS transistors serve as the drivers and a single gate-grounded PMOS transistor serve as the load. In this logic family, logic high output is at the power supply voltage, and logic low output is not necessarily at the ground but is ratioed. Pseudo-NMOS logic has high static power dissipation.
Pull-Down Network (PDN)
In various logic families, the pull-down network consists of a group of transistors responsible for driving the logic output to ‘0’ according to the truth table. The effective resistance of the PDN affects the high-to-low time constant of the circuit. In CMOS logic, the PDN is made up of NMOS transistors.
Pull-Up Network (PUN)
In CMOS logic, the pull-up network comprises PMOS transistors responsible for driving the logic output to ‘1’ in accordance with the truth table. The effective resistance of the PUN influences the low-to-high time constant of the circuit.
Punchthrough is a phenomenon observed in transistors, especially short-channel ones, where the depletion regions around the source and drain regions come into contact with each other. This typically occurs at high voltages exceeding the saturation voltage. When punchthrough happens, it can lead to the flow of a significant current, potentially damaging the device.
PVD (Physical Vapor Deposition)
PVD is a deposition method used to apply a thin film of material onto a substrate, often used for metal layers in semiconductor fabrication. It involves creating a vapor of the material and allowing it to condense on the substrate. One common PVD technique is sputtering, where high-energy particles strike a target material, creating an aerosol that deposits on the wafer.