VLSI DESIGN PROCESS

THE VLSI DESIGN PROCESS

A typical digital design flow is as follows:

* Specification

* Architecture

* RTL Coding

* RTL Verification

* Synthesis

* Backend

All modern digital designs start with a designer writing a hardware description of the IC (using HDL or Hardware Description Language) in Verilog/VHDL. A Verilog or VHDL program essentially describes the hardware (logic gates, Flip-Flops, counters etc) and the interconnect of the circuit blocks and the functionality. Various CAD tools are available to synthesize a circuit based on the HDL. The most widely used synthesis tools come from two CAD companies. Synposys and Cadence.

Without going into details, we can say that the VHDL, can be called as the "C" of the VLSI industry. VHDL stands for "VHSIC Hardware Definition Language", where VHSIC stands for "Very High Speed Integrated Circuit". This languages is used to design the circuits at a high-level, in two ways. It can either be a behavioural description, which describes what the circuit is supposed to do, or a structural description, which describes what the circuit is made of. There are other languages for describing circuits, such as Verilog, which work in a similar fashion.

Both forms of description are then used to generate a very low-level description that actually spells out how all this is to be fabricated on the silicon chips. This will result in the manufacture of the intended IC.

A typical analog design flow is as follows:

In case of analog design, the flow changes somewhat.

* Specifications

* Architecture

* Circuit Design

* SPICE Simulation

* Layout

* Parametric Extraction / Back Annotation

* Final Design

* Tape Out to foundry

While digital design is highly automated now, very small portion of analog design can be automated. There is a hardware description language called AHDL but is not widely used as it does not accurately give us the behavioral model of the circuit because of the complexity of the effects of parasitic on the analog behavior of the circuit. Many analog chips are what are termed as “flat” or non-hierarchical designs. 

This is true for small transistor count chips such as an operational amplifier, or a filter or a power management chip. For more complex analog chips such as data converters, the design is done at a transistor level, building up to a cell level, then a block level and then integrated at a chip level. 

Not many CAD tools are available for analog design even today and thus analog design remains a difficult art. SPICE remains the most useful simulation tool for analog as well as digital design

VLSI Implementation Media

VLSI Implementation Media

Media requiring fabrication:

* Full Custom - design and physical layout at transistor level
* Standard Cell - design and physical layout at gate/flip-flop level
* Gate Array - design and physical layout at gate level (like standard cell but with some prefabrication of wafer)


Prefabricated media:
* Field Programmable Gate Arrays (FPGAs) - design at gate/flip-flop or register transfer level
* Complex Programmable Logic Devices (CPLDs) - design at gate/flip-flop or register transfer level
* Programmable Logic Devices (PLDs) - design at gate/flip-flop level 
* System-on-Chip (SoC) may incorporate several of these implementation media on a single chip

History of VLSI

VLSI, Very Large Scale Integration

History of VLSI

Late 40s 
Transistor invented at Bell Labs


Late 50s 
First IC (JK-FF by Jack Kilby at TI)


Early 60s 
Small Scale Integration (SSI)     
10s of transistors on a chip


Late 60s 
Medium Scale Integratoin (MSI) 
100s of transistors on a chip


Early 70s 
Large Scale Integration (LSI) 
1000s of transistor on a chip


Early 80s 
VLSI 10,000s of transistors on a chip (later 100,000s & now 1,000,000s)

Ultra LSI is sometimes used for 1,000,000s

Origins of VLSI

Origins of VLSI

Much development motivated by WWII need for improved electronics, especially for radar

* 1940 - Russell Ohl (Bell Laboratories) - first pn junction

* 1948 - Shockley, Bardeen, Brattain (Bell Laboratories) - first transistor

* 1956 Nobel Physics Prize

* Late 1950s - purification of Si advances to acceptable levels for use in electronics

* 1958 - Seymour Cray (Control Data Corporation) - first transistorized computer - CDC 1604

* 1959 - Jack St. Claire Kilby (Texas Instruments) - first integrated circuit - 10 components on 9 mm2

* 1959 - Robert Norton Noyce (founder, Fairchild Semiconductor) - improved integrated circuit

* 1968 - Noyce, Gordon E. Moore found Intel

* 1971 - Ted Hoff (Intel) - first microprocessor (4004) - 2300 transistors on 9 mm2

Since then - continued improvement in technology has allowed for increased performance as predicted by Moore’s Law

Why VLSI

Why VLSI?

• Integration improves the design
• Lower parasitics = higher speed
• Lower power consumption
• Physically smaller
• Integration reduces manufacturing cost - (almost) no manual assembly

What is VLSI

What is VLSI?

VLSI stands for "Very Large Scale Integration". This is the field which involves packing more and more logic devices into smaller and smaller areas.Thanks to VLSI, circuits that would have taken boardfuls of space can now be put into a small space few millimeters across! 

Very-large-scale integration (VLSI) is the process of creating integrated circuits by combining thousands of transistors into a single chip. VLSI began in the 1970s when complex semiconductor and communication technologies were being developed. The microprocessor is a VLSI device

This has opened up a big opportunity to do things that were not possible before. VLSI circuits are everywhere ... your computer, your car, your brand new state-of-the-art digital camera, the cell-phones, and what have you. VLSI has been around for a long time, there is nothing new about it ... but as a side effect of advances in the world of computers, there has been a dramatic proliferation of tools that can be used to design VLSI circuits. 

Alongside, obeying Moore's law, the capability of an IC has increased exponentially over the years, in terms of computation power, utilisation of available area, yield. The combined effect of these two advances is that people can now put diverse functionality into the IC's, opening up new frontiers

The first semiconductor chips held two transistors each. Subsequent advances added more and more transistors, and, as a consequence, more individual functions or systems were integrated over time. The first integrated circuits held only a few devices, perhaps as many as ten diodes, transistors, resistors and capacitors, making it possible to fabricate one or more logic gates on a single device. Now known retrospectively as small-scale integration (SSI), improvements in technique led to devices with hundreds of logic gates, known as medium-scale integration (MSI). Further improvements led to large-scale integration (LSI), i.e. systems with at least a thousand logic gates. Current technology has moved far past this mark and today's microprocessors have many millions of gates and billions of individual transistors.

At one time, there was an effort to name and calibrate various levels of large-scale integration above VLSI. Terms like ultra-large-scale integration (ULSI) were used. But the huge number of gates and transistors available on common devices has rendered such fine distinctions moot. Terms suggesting greater than VLSI levels of integration are no longer in widespread use.

As of early 2008, billion-transistor processors are commercially available. This is expected to become more commonplace as semiconductor fabrication moves from the current generation of 65 nm processes to the next 45 nm generations (while experiencing new challenges such as increased variation across process corners). A notable example is Nvidia's 280 series GPU. This GPU is unique in the fact that almost all of its 1.4 billion transistors are used for logic, in contrast to the Itanium, whose large transistor count is largely due to its 24 MB L3 cache. Current designs, as opposed to the earliest devices, use extensive design automation and automated logic synthesis to lay out the transistors, enabling higher levels of complexity in the resulting logic functionality. Certain high-performance logic blocks like the SRAM (Static Random Access Memory) cell, however, are still designed by hand to ensure the highest efficiency

VLSI PROJECT LIST, IEEE 2010

VLSI PROJECT LIST, IEEE 2010 

·         Design of SHA-1 Algorithm Based on FPGA

·        Algorithm of Binary Image Labeling and Parameter Extracting Based on FPGA

·        An FPGA-based Architecture for Linear and Morphological and Image filtering

·        Development of a New Breath Alcohol Detector without Mouthpiece to Prevent Alcohol-Impaired Driving

·        FPGA implementation for humidity and temperature remote sensing system

·        Hardware realization of shadow detection algorithm in fpga

·        Image Edge Detection Based on FPGA

·        Performance Efficient FPGA Implementation of Parallel 2-D MRI Image Filtering Algorithms using Xilinx System Generator

·        Recognition FPGA system for detection of anomalies in mammograms

·        RFID-based Hospital Real-time Patient Management System

·        Solid waste monitoring and management using RFID, GIS and GSM

·        Sort Optimization Algorithm of Median Filtering Based on FPGA

·        The Realization of Precision Agriculture Monitoring System Based on Wireless Sensor Network

www.ncct.in, ncctchennai@gmail.com, 2823 5816, 98411 93224