Semiconductors: Overview & Glossary

Integrated Circuit (IC)

The integrated circuit, also known as microcircuit, microchip, silicon chip, computer chip or chip, consists of a number (a few to millions) of devices manufactured and interconnected on a single semiconductor substrate. An IC is a miniaturized electronic circuit. These devices include transistors, diodes, resistors, capacitors, and other electronic components.

Hybrid Integrated Circuit (= Hybrid Circuit)

Miniaturized electronic circuit constructed of individual devices, bonded to substrate or printed circuit board (PCB), includes

Ø Semiconductor devices: transistors + diodes

Ø Passive components: resistors, inductors, + capacitors

Provides the same functionality as monolithic integrated circuit, the difference between the devices is how they are constructed and manufactured.

Semiconductor Devices

Electronic components that exploit electronic properties of semiconductor materials like silicon, germanium, gallium arsenide, etc. Use electronic conduction in solid state. Devices are manufactured as single discrete devices and as integrated circuits (ICs). Semiconductor materials are so useful because the behavior of semiconductor is easily manipulated by the addition of impurities through doping

Transistor

This is a semiconductor device that uses a small amount of voltage or electrical current to control a larger change in voltage or current. It is the fundamental building block of circuitry governing the operation of computers, cell phones, and all other modern electronics.

Because of its fast response and accuracy it is used in a wide variety of digital and analog functions, including amplification, switching, voltage regulation, signal modulation, and oscillators. Transistors may be packaged individually or as part of an integrated circuit chip

In analog circuits, transistors are used in amplifiers (direct current amplifiers, audio amplifiers, radio frequency amplifiers) and to regulate power supplies. In digital circuits, transistors function as electronic switches, but rarely as discrete devices, almost always being incorporated in Monolithic ICs.

Transistors are the primary component in practically all modern electronics. Individual transistors are still used (referred to as discrete), but the vast majority of transistors are fabricated into integrated circuits. In 2006, a logic gate comprises of about 20 transistors where an advanced microprocessor uses as many as 1.7B transistors (MOSFETs).

Types of IC

There are three types of integrated circuits

I. Digital

Use binary mathematics to process "one" and "zero" signals through logic gates, flip-flops, and multiplexers. Digital IC’s can be generally be classified into three types

1) Processor (microprocessor, microcontroller, or DSP)

2) Logic Gates

3) Random Access Memory (RAM)

II. Analog

We live in an analog world filled with continuous analog signals such as light, temperature, sound, electrical fields, and magnetic fields.

These electronic systems process continuous signals, such as a radio frequency or voltage, using some property of the medium to convey the signal's information. These devices represent information by changing the signal's voltage, current, frequency, or total charge. Information is conveyed by altering a physical form like sound, light, temperature, pressure, or position

Analog vs. Digital

Analog circuits are much faster than digital circuits because a single digital signal is restricted to a one or zero while an analog signal can represent a much broader range of values. Because analog signals are continuous and represent far more values than their digital counterparts they are more susceptible to being altered by external forces (called noise). While less susceptible to data loss due to noise digital systems can be more fragile because the loss or misrepresentation of a single piece of digital data can change the meaning of large chunks of a system’s data.

Analog circuits use less energy than digital circuits; to accomplish the same calculations and signal processing.

III. Mixed Signal

Circuits that interface or translate between digital circuits and analog circuits

Microprocessors

A central processing unit (CPU) on a single IC. A Central Processing Unit (CPU) is a certain type of logic machine that can execute computer programs.

Microcontroller

Similar to a microprocessor, but emphasizes self-sufficiency (integrates I/O, RAM, Flash or ROM, peripherals, and clock generator along with the CPU) and low cost. Represent the majority of the microprocessor market and are common in embedded systems. A typical car will have dozens of microcontrollers.

DSP - Digital Signal Processing

A digital signal processor is a type of microprocessor designed to specifically for digital signal processing. Digital signal processing can take place in dedicated digital signal processors, fixed logic ASICs, or FPGAs. Some of the highest performing DSP systems are implemented in FPGAs because processing can be done on the chips in a parallel fashion

SoC – System on a chip

An IC that acts as an entire subsystem (microprocessor, memory, peripherals, custom logic, etc) by integrating all computer or electronic system components into a single integrated circuit (chip). This chip can contain digital, analog, mixed-signal, and radio-frequency functions. The SoC designer uses a software development environment to integrate the IP blocks and/or a CAD tool to integrate the hardware IP blocks.

A SoC often includes various functions

ü One or more processors

ü Memory (ROM, RAM, Flash)

ü Timing sources (oscillators and phase-locked loops)

ü Peripherals

ü I/O (USB, Ethernet)

ü Analog converters

ü Voltage regulators and power management circuits

Embedded System

A broad term describing special-purpose computer system designed to perform a limited number of functions; as opposed to a generic system like a PC. Embedded systems are often embedded as part of a larger system such as a car, airplane, washing machine, microwave, digital watch, MP3 player, TV, or traffic light. Embedded systems may have a single microcontroller chip or may have multiple units and peripherals networked together.

Random Access Memory (RAM)

RAM is a type of computer data storage. The word random denotes that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data. Other types of data storage, such as tapes, magnetic discs and optical discs, rely on the physical movement of the recording medium or a reading head; so they are not random.

Logic Gates

These are the fundamental unit of digital electronics. Performs a logical operation on one or more digital signals (logic inputs) and produces a single logic output.

Electronic Design Automation (EDA)

Tools for designing and producing electronic systems, in this context specifically referring to integrated circuits

Electronic System-Level (ESL) Design

An emerging electronic design methodology focused on higher abstraction level concerns. ESL models the entire system using a high-level language like C or C++. Has become an established approach at most of leading System-on-a-chip (SoC) design companies, and is being used increasingly in system design. ESL is evolving to enable embedded system design, verification, and debugging of the hardware and software implementation of custom SoC, system-on-FPGA, system-on-board, and entire multi-board systems.

Hardware Description Language (HDL)

A software language that describes the layout of electronic circuits. The language’s syntax and semantics revolve around representations of time and concurrency which are the primary attributes of hardware. The most common HDLs are the two standards VHDL and Verilog HDL.

It is possible to represent hardware semantics with traditional programming languages like C or C++, but that requires using large, unwieldy class libraries because the languages do not have built in support for explicitly expressing time. A hardware description language describes how to build logic. A software programming language generates instructions that a microprocessor uses to make calculations and move data.

Intellectual Property Core (IP Core or IP block)

A re-usable block of logic, that allows designers to plug in existing components that have been tested, optimized, and validated. Some examples of IP cores would be an embedded processor, MP3 codec, encryption, and PCI interface. IP cores are for chip design what a library (DLL) is for computer programming.

Analog and mixed-signal logic generally require a lower-level, physical description so they are distributed as hard cores. Digital Logic cores can be offered in many formats:

Ø Soft cores that follow the SPR design-flow (synthesis, placement and route)

§ Generic gate netlists (most common)

§ Synthesizable cores

o Offered in the form of a hardware description language, like Verilog or VHDL, allowing customer modification, at the functional level.

Ø Hard cores, where transistor layouts must obey the target foundry's process design rules and cannot be meaningfully modified by the customer. A fully routed design. Hard cores offer a lower level representation so provide better predictability, but force lock-in to a specific foundry.

The IP market was only a few thousand dollars in the late 1980s; by 2003 the market was over a billion dollars.

Netlist

A description of the connectivity of an electronic design. It is a Boolean-algebra representation (gates, standard cells) of the IP's logical-function. It is comparable to assembly-code listing for a high-level program application. The vendor is protected from reverse-engineering, while maintaining portability to multiple foundry targets.

Logic - ASIC’s & Programmable

ASIC - Application Specific Integrated Circuit

§ A custom chip that uses fixed logic, custom built for the particular product or end use

§ Combines a collection of functions; typically designed by or for one customer

§ Designers create using a hardware description language (HDL) like Verilog or VHDL

ASSP - Application Specific Standard Product

§ Integrated circuit that implements a specific function that appeals to a wide market

§ Available as off-the-shelf components, examples: IC’s that perform video and/or audio encoding and/or decoding

Structured ASICs

Also known as Platform ASICs, consist of a large IP core like a processor, DSP unit, peripherals, standard interfaces, integrated memories SRAM, and a block of reconfigurable uncommitted logic. This shift is largely because ASIC devices are capable of integrating such large blocks of system functionality and "system on a chip" requires far more than just logic blocks.

Structured ASICs are available off the shelf, but still require some custom fabrication. Only a small number of chip layers must be custom-produced or interconnected by the customer. Structured ASICs bridge the gap between full custom ASICs and FPGAs.

PLD - Programmable Logic Device

§ Semiconductor devices that can easily be programmed, using development software running on a PC or workstation.

§ Any programmable logic device which encompasses PALs, SPLDs, CPLDs and FPGAs.

CPLD - Complex Programmable Logic Device

Has logic densities of usually less than 10,000 gates and includes on chip non-volatile memory.

PAL - Programmable Array Logic

The earliest and, in terms of logic density, the simplest form of a programmable logic device.

FPGA Overview

FPGA - Field-Programmable Gate Array

Programmable semiconductor devices that are based around a matrix of configurable logic blocks (CLBs) connected via programmable interconnects. Programmed to desired application or functionality requirements

Field Programmable Gate Arrays (FPGAs) are programmable semiconductor devices that are based around a matrix of configurable logic blocks (CLBs) connected via programmable interconnects. As opposed to Application Specific Integrated Circuits (ASICs) where the device is custom built for the particular design, FPGAs can be programmed to the desired application or functionality requirements.

Although one-time programmable (OTP) FPGAs are available, the dominant type is SRAM based which can be reprogrammed as the design evolves.

Platform FPGA

The first FPGA was introduced in 1985 by Xilinx. Its fabric was a small array of configurable lookup tables and flip-flops. It has since been augmented with blocks of IP like RAMs, multipliers, general purpose processor cores, DSP cores, etc. Platform FPGA’s are standard FPGAs targeted at multiple applications such as embedded processing, digital signal processing, etc (basically a SoC). Platform FPGAs are augmented with blocks of hard IP like RAM, processor cores, DSP, multipliers, etc.

CLB - Configurable Logic Blocks

The basic logic unit in an FPGA; exact numbers and features vary from device to device, but every CLB consists of a configurable switch matrix with 4 or 6 inputs, some selection circuitry (MUX, etc), and flip-flops. The switch matrix is highly flexible and can be configured to handle combinatorial logic, shift registers, or RAM.

Interconnect

While the CLB provides the logic capability, flexible interconnect routing routes the signals between CLBs and to and from I/Os. Routing comes in several flavors, from that designed to interconnect between CLBs to fast horizontal and vertical long lines spanning the device to global low-skew routing for Clocking and other global signals. The design software makes the interconnect routing hidden to the user unless specified otherwise, significantly reducing design complexity.

SelectIO (IOBs)

Today’s FPGAs provide support for dozens of I/O standards thus providing the ideal interface bridge in your system. I/O in FPGAs is grouped in banks with each bank independently able to support different I/O standards. Today’s leading FPGAs provide over a dozen I/O banks, thus allowing flexibility in I/O support.

Memory

Embedded Block RAM memory is available in most FPGAs, which allows for on-chip memory in your design. These allow for on-chip memory for your design. Xilinx FPGAs provide up to 10 MB of on-chip memory in 36 KB blocks that can support true dual-port operation.

Clock Management

Digital clock management is provided by most FPGAs in the industry (all Xilinx FPGAs have this feature). The most advanced FPGAs from Xilinx offer both digital clock management and phase-looped locking that provide precision clock synthesis combined with jitter reduction and filtering.