VLSI refers to microchips containing hundreds of thousands of transistors used for computer processing. The VLSI design process begins with specifying the system and breaks it down into functional blocks and logic gates. It involves multiple phases of design representation from behavioral to layout. A top-down or bottom-up methodology is used, with a combination being common today. The goal is to take a system specification through functional design, logic design, circuit design, and physical design to produce a layout for chip fabrication.

2. Introduction
What is VLSI?
VLSI (very large-scale integration) is the current level of
computer microchip miniaturization and refers to microchips
containing in the hundreds of thousands of transistor s. LSI
(large-scale integration) meant microchips containing
thousands of transistors.
What is the Use of VLSI?
VLSI APPLICATION. VLSI stands for Very Large Scale
Integration. It's used in creating so many chips and circuits
on a single mini chip of silicon.

3. Introduction
Requirements study
specification
implementation
validation
What do I have to design?
How do I do it?
Have I implemented
What I intended to?
About any design..
market

4. VLSI SYSTEM DESIGN FLOW
V. ANURADHA
VLSI Design cycle:
VLSI design cycle start with a formal
specification of a VLSI chip, follows
a series of steps, and eventually
produces a packaged chip.

5. Simplified VLSI Design Flows
System Specification
Functional
(Architecture) Design
Functional Verification
Logic Design
Logic Verification
Circuit Design
Circuit Verification
Physical Design
Physical Verification
Front End Back End
Synthesis Phase Layout Phase
Circuit
Representation
Layout
Representation
Behavioral
Representation
Logic(Gate-Level)
Representation

6. VLSI SYSTEM DESIGN FLOW
V. ANURADHA
Four Levels of Design Representation
Behavioral
Representation
Logic (Gate-Level)
Representation
Circuit
(Transistor-Level)
Representation
Layout
Representation
Functional Blocks, FSM
Logic Blocks, Gates
Transistor Schematics
Physical Devices

7. VLSI Design flow
VLSI SYSTEM DESIGN FLOW
V. ANURADHA

8. Design Methodology
There are two basic types of digital design
methodologies
Top-Down design methodology
Bottom-Up design methodology
Top-Down Design Methodology
 Define top-level block and identify the sub-
blocks
 divide sub-block until we come to leaf cells

9. Design Methodology
Bottom-Up Design Methodology
identify building block that are available for us
build a bigger cells using these block
continue build a cell until we build top level
the
A combination of Top-Down and Bottom-Up
design are used in today’s digital design
top-level

10. Top-Down Design Methodology
VLSI SYSTEM DESIGN FLOW
V. ANURADHA
Top Level Block
Sub Block 1 Sub Block 1
Sub Block 1
Leaf
Cell
Leaf
Cell
Leaf
Cell
Leaf
Cell
Leaf
Cell
Leaf
Cell

11. Bottom-Up Design Methodology
Top Level Block
Macro Cell 1 Macro Cell 3
Macro Cell 2
Leaf
Cell
Leaf
Cell
Leaf
Cell
Leaf
Cell
Leaf
Cell
Leaf
Cell

12. Simplified view of VLSI design Flow
Top Down
(algorithm
Bottom Up
(physical)

13. Y-Chart

14. System Specification
 First step of design process is to lay down
the specification of the system.
 High level representation of the system.
 Factors considered:
 Performance,Functionality,Physical
dimension,Design technique,Fabrication
technology
 It is a compromise between market
requirements, technological and economical
viability.

15. System Specification
The end results are specifications of
 Size,Speed,Power and Functionality
of the VLSI system
 Basic architecture

16. Functional Design
 Main functional units, Interconnect requirements
of the system are identified
 The area, power and other parameters of each unit
are estimated
 The key idea is to specify behavior, in terms of
Input,Output,Timing of each unit
 The outcome of functional design is usually a
timing diagram
 This information leads to improvement of the
overall design process and reduction of
complexity of the subsequent phases

17. Logic Design
Design the logic, that is,
Boolean expressions,word width, register allocation,
etc.
The outcome is called an RTL (Register Transfer
Level) description. RTL is expressed in a HDL
(Hardware Description Language), such as VHDL
and Verilog.

18. Circuit Design
 The purpose of the circuit design is to develop a
circuit representation based on the logic design.
 The Boolean expression can be converted into a
circuit representation by taking into consideration
the speed and power requirements of the original
design.
 Design the circuit including gates, transistors,
interconnections, etc. The outcome is called a
netlist.
 Circuit simulation is used to verify the correctness
and timing of component

19. Physical Design
Given a circuit after logic
synthesis, to convert it into a
layout

20. Overall design process