an overview of vlsi

7/29/2019 An Overview of VLSI

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A Paper Presentation on

by

P.Manikanta K.Anvesh Varma(096N1A0447) (096N1A0424)

From the Department of Electronics and Communication Engineering,

SRINIVASA INSTITUTE OF ENGINEERING AND TECHNOLOGY,

CHEYYERU.


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Introduction to VLSI Circuits and Systems


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Outline Introduction

Complexity and Design

Basic Concepts


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Introduction IC: Integrated Circuits, many transistors on one chip

VLSI:VeryLarge Scale Integration, amodern technology of IC designflow

MOS: Metal-Oxide-Silicon transistor (also called device)

CMOS: ComplementaryMetal Oxide Semiconductor Fast, cheap, low power transistors High integration, low cost n-type MOS (NMOS): Current of Electrons p-type MOS (PMOS): Current of Holes

First: How to build your own simple CMOS chip CMOS transistors Building logic gates from transistors Transistor layout and fabrication

Rest of the course: How to build a good CMOS chip!!


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Silicon Lattice Transistors are built on a silicon substrate

Silicon is a Group IV material

Forms crystal lattice with bonds to four neighbors


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Dopants Silicon is a semiconductor

Pure silicon has no free carriers and conducts poorly

Adding dopants increases the conductivity

Group V: extra electron (n-type)

Group III: missing electron, called hole (p-type)


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Complexity and Design Creating a design team provides

a realistic approach toapproaching a VLSI project, as itallows each person to study small

sections of the system Needing hundreds of engineers,

scientists, and technicians

Needing hierarchy design and

many different

Level Views

Everyone of each level depends

upon the Computer-AidedDesign (CAD) tools Figure 1.1 The VLSI design funnel


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VLSI Design Flow

Design Code

FloorPlanning

IC LayoutFunctionalSimulation

IC Design

SynthesisSimulation

LayoutSimulation

DesignRule

Check


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Design Hierarchy (1/2) System specifications: is defined in both

general and specific terms, such as functions,speed, size, etc.

Abstract high-level model: containsinformation on the behavior of each blockand the interaction among the blocks in the

system Logic synthesis: To provide the logic design of

the network by specifying the primitive gatesand units needed to build each unit

Circuit design: where transistors are used asswitches and Boolean variables are treated asvary voltage signals

Physical design: the network is built on a tinyarea on a slice of silicon

Manufacturing: a completed design process ismoved on to the manufacturing line

Figure 1.2 General overviewof the design hierarchy


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Design Hierarchy (2/2) Hierarchical design

Top-down design the initial work is quite abstract and

theoretical and there is no directconnection to silicon until many stepshave been completed

Acceptable in modern digital systemdesign

Co-design with combining HW/SW iscritical

Similar to Cell-based Design Flow Bottom-up design

starts at the silicon or circuit level andbuilds primitive units such as logic gates,adders, and registers as the first steps

Acceptable for small projects Similar to Full-custom Design Flow

An example of a design hierarchy inFigure 1.3 an instruction design of a

microprocessorFigure 1.3 A simple designflow for a microprocessor


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VLSI Chip Types At the engineering level, digital VLSI chips are classified by the

approach used to implement and build the circuit Full-custom Design: where every circuit is custom designed for the

project Extremely tedious

Time-consuming process Application-Specific Integrated Circuits (ASICs): using an

extensive suite of CAD tools that portray the system design in termsof standard digital logic constructs Including state diagrams, functions tables, and logic diagram Designer does not need any knowledge of the underlying electronics or

the physic of the silicon chip Major drawback is that all characteristics are set by the architectural

design

Semi-custom Design: between that of a full-custom and ASICs Using a group of primitive predefined cells as building blocks, called cell

library


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Basic Concepts:

Today, the most powerful topic

is System-on-Chip (SoC) thatusing bonding padtechnology asFigure 1.5 shows

Figure 1.5 Bonding pad

frame for interfacing


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Scenario in India??? HUGE outsourcing

Loads of startups (WHY?)

VLSI design is nowhere a single nation job Fabrication labs (fabs) in USA getting sold out

India getting 4 fabs by next year!


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ANY QUERIES

THE END


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an overview of vlsi

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