VLSI Design Tutorial

VLSI Design Tutorial

VLSI Design is a subbranch of electronics engineering that deals with the study, design, and manufacturing of VLSI (Very Large Scale Integration) ICs. VLSI is an IC manufacturing technology that involves the integration of more than 10,000 transistors onto a single chip. VLSI ICs and VLSI design have become the heart of modern electronics, as this technology is allowing to develop more complex ICs having features like very small size and low power consumption.

Today, VLSI based integrated circuits are widely being used in a number of electronic devices, ranging from a smartphone or smart watch to supercomputers and advanced control systems.

This tutorial is designed to explain some fundamental concepts of VLSI design, its advantages and applications in real-world systems.

What is VLSI?

VLSI stands for Very Large Scale Integration. VLSI is an IC manufacturing technology that allows to combine more than ten thousand transistors onto a single chip. This technology was introduced in the late 1970s and revolutionized the semiconductor industry by allowing to design compact, fast, and more efficient integrated circuits and their applications in various electronic systems.

What is VLSI Design?

VLSI design can be defined as a process of creating the layout and defining the functionality of integrated circuits using very large-scale integration of transistors onto a single chip. It is used for developing ICs to perform complex calculations, data processing, and other high-level computation tasks. VLSI design is paving the path for development of advanced digital systems with reduced form factor.

VLSI Design Process

VLSI design is a multi-stage process that helps transforming a system specification into a functional integrated circuit that can be manufactured.

The step-by-step explanation of the VLSI design is provided here −

Step 1 − The VLSI design process initiates with defining the system specifications and constraints like functionality, speed, power consumption, operating temperature, etc. Hence, this step provides a blueprint of the entire VLSI design process.

Step 2 − In this step, the overall architecture of the VLSI chip is defined. It involves the processes like partitioning of design into functional blocks, interconnection of blocks, and performance evaluation of the IC.

Step 3 − In this step, the logic design of VLSI chip takes place. Here, the architectural design of the IC is converted into a detailed logic representation. The processes performed during logic design include logic gate implementation, sequential logic and control path design, and verification of functionality of the logic design.

Step 4 − This step of VLSI design process involves the schematic design of the IC. In this step, a schematic of IC is created according to the logic design created in the previous step. In schematic design, functions like component listing, interconnection of components, organization of blocks, power consumption estimation, etc. are performed. Hence, the schematic design provides a refined version of the logic design.

Step 5 − After obtaining the schematic design, next step is the physical design of the VLSI IC. The physical design transforms the logic design into a physical layout. Physical design involves functions like space allocation for functional blocks within the chip, components placement, clock signal distribution, components connections, design rule verification, etc.

Step 6 − Once the physical design is prepared, it is tested to verify that it meets the design specifications and free from errors.

Step 7 − After testing and verification, the VLSI design process reaches to the fabrication stage, which takes place in a semiconductor foundry. The fabrication process involves the functions like etching patterns onto a semiconductor wafer, creating and interconnecting transistor layers, doping semiconductors to create electronic properties, etc.

Step 8 − Finally, the fabricated wafers are diced into individual chips and packed into an IC packaging to provide protection and electrical connections.

Step 9 − At the end, the individual chips are tested to ensure that they will perform functions correctly.

Types of VLSI Design

The most common types of VLSI designs are explained here –

1. Programmable VLSI Design

Programmable VLSI design is the process of creating integrated circuits that can be easily reconfigured to perform different functions. The programmable logic elements like FPGAs, CPLDs, etc. are used as the fundamental building blocks in this VLSI design. These programmable elements contain a set of digital logic gates that can be programmed or reprogrammed to perform different functions.

Programmable VLSI design is mainly used in applications like prototyping, AI applications, or in systems that require frequent reconfiguration.

2. Non-Programmable VLSI Design

Non-programmable VLSI design is completely opposite to the programmable design. It involves the development of integrated circuits whose functionality cannot be modified once they have been fabricated. Non-programmable VLSI design is mainly used for producing ICs for high-performance systems, as these VLSI ICs provide a great control over the operations of the systems.

Custom design logic circuits are used for creating non-programmable VLSI designs. Non-programmable VLSI design is widely used in smartphone processors, GPU chips, or ICs used in medical devices.

Advantages of VLSI Design

• VLSI design offers high integration density and allows to integrate a large number components onto a single chip.
• VLSI design, especially programmable design, provides flexibility in reconfiguration of the IC.
• VLSI design requires less development time, due to availability of pre-designed and pre-tested elements.
• VLSI design allows to develop circuits having optimized speed and performance.
• VLSI designs have high energy efficiency.
• At large scale production, VLSI design offers high-cost efficiency.
• VLSI design provides precise control over the circuit operations and ensures reliability.

Disadvantages of VLSI Design

• VLSI design, especially programmable design, provides a reduced speed and efficiency in certain high-performance applications.
• The degree of programming flexibility increases the power consumption and cost for the VLSI design.
• Non-programmable VLSI designs cannot be reconfigured and hence not suitable for applications that require frequent updates.
• VLSI design requires technical expertise.
• At low-volume production, VLSI design becomes uneconomical.
• VLSI design requires extensive testing to ensure the desired functionality.
• Non-programmable VLSI design has limited reusability.

Applications of VLSI Design

VLSI design is the backbone of the most modern digital systems. Some key examples highlighting the applications of VLSI design are as follows −

• In consumer electronics, VLSI design is used to design and manufacture processors, memory, and communication modules.
• VLSI design is also used to develop high performance GPU ICs used in gamming consoles.
• VLSI design is also used to develop compact and low-power ICs for smartwatches and other wearable devices.
• Chips used in autonomous vehicles for navigation, object detection, lane detection, etc. are also designed using VLSI technology.
• VLSI design is also used for developing ICs used in telecommunication networks for high-speed data transfer.

What You Will Learn in VLSI Design?

The topics covered in this VLSI design tutorial are described in the following table −

• VLSI Design - Digital System − This chapter provides an overview of some basic concepts of digital systems in VLSI design such as VLSI design flow, Y chart, etc.
• FPGA Technology − In this chapter, you will find a discussion on introduction and advantages of FPGA technology used in VLSI design.
• MOS Transistor − This chapter explains the construction, working, and characteristics of MOS (Metal Oxide Semiconductor) transistors used in VLSI design.
• MOS Inverter − This section describes the principle of operation and types of MOS inverters employed in VLSI technology.
• Combinational MOS Logic Circuits − This chapter explains various combinational MOS logic circuits such as CMOS logic gates, NOR gate, NAND gate, etc.
• Sequential MOS Logic Circuits − In this chapter, you will learn about different types of sequential MOS logic circuits like SR latch, JK latch, etc.
• VHDL Introduction − This section provides an overview of VHDL programming and modeling.
• VHDL Programming Combinational Circuits − This chapter explains VHDL programming for some common types of combination circuits like adders, subtractors, multiplexer, etc. used in VLSI design.
• VHDL Programming for Sequential Circuits − In this section, you will learn to write VHDL code for sequential circuits like latches, flip-flops, counters, etc.
• Verilog Introduction − This chapter discusses the fundamentals of a popular hardware description language, Verilog.
• Behavioural Modelling and Timing in Verilog − This section explains two important concepts of HDL in Verilog namely, behavioural modelling and timing.

Who Should Learn VLSI Design?

This tutorial has been prepared for the students who want to know about the VLSI Technology. The students will also be able to know about the VHDL and Verilog program coding.

The content provided in this VLSI design tutorial is also useful for the following audience –

• Engineering students specializing in electrical, electronics, or computer science
• Professionals working in the field of semiconductor technology
• Electronics enthusiasts
• Engineers or professionals working in VLSI industry, etc.

Prerequisites to Learn VLSI Design

This tutorial is written in a lucid and beginner friendly style and hence no prior knowledge of the subject is needed. However, a basic understanding of electronic circuits, digital electronics, semiconductor physics, and basic programming concepts will make it easy to grasp the concepts covered here.

FAQs on VLSI Design

This section is included to briefly answer some of the most Frequently Asked Questions (FAQs) on VLSI Design.

1. Is VLSI design a good career option?

VLSI (Very Large Scale Integration) design is a branch of electronics that deals with developing, verifying, and testing integrated circuits having millions or billions of transistors and other components onto a single chip.

VLSI design can be a good career choice for an electronic engineer, because of the following key reasons −

• Growing demand of integrated circuits
• High salaries
• Foundation for many industries like robotics, IoT, AI, etc.
• Constant learning opportunities, etc.

2. Is VLSI software or hardware?

VLSI is a subset of hardware design technology that deals with integration and miniaturization of millions of electronic components onto a single chip.

3. Does VLSI have coding?

Yes, VLSI does require coding for various purposes like design, verification, automation, etc. For this, it uses various hardware description languages like Verilog, Perl, VHDL, etc.

4. What are the 5 levels in VLSI design?

The 5 key levels in VLSI design are as follows −

• Architectural design level
• Functional design level
• Logic design level
• Circuit design level
• Physical design level

5. Why is VLSI used?

VLSI is an IC manufacturing technology mainly used to design and produce small, powerful, energy efficient, and reliable integrated circuits for a variety of electronic devices and systems.