Undergraduate Curriculum Development for Digital Integrated Circuit Design

doi:10.4236/ce.2012.326128

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Creative Education

2012. Vol.3, Special Issue, 856-858

Published Online October 2012 in SciRes (http://www.SciRP.org/journal/ce) http://dx.doi.org/10.4236/ce.2012.326128

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Undergraduate Curriculum Development for Digital Integrated

Circuit Design

Xin Chen

Department of Electronic Science and Technology, Tongji University, Shanghai, China

Email: [email protected]

Received August 29th, 2012; revised September 3 0th, 2012; accepted Octob e r 11th, 2012

This article describes the development of a Digital Integrated Circuit Design curriculum, which includes

how to select the design level and how to implement the design. The curriculum is for the undergraduates

in grade four, whose major is microelectronics. The development is in the background of very large scale

integrated circuits. Since the popular design flow is a hierarchy of abstraction levels, the goal of the cur-

riculum is to develop the students’ ability to design an actual circuit from scratch. Comparison is provided

from two aspects. The first aspect is the contents of various published textbooks. The second aspect is the

contents of similar courses in famous universities.

Keywords: Digital Integrated Circuit; Design Abstraction Level; Transistor Level; Gate Level; Hardware

Description Language

Introduction

Microelectronics is the base for modern information tech-

nology. And the digital integrated circuits are those who are

based on binary computation, which are the compositions for

microprocessors and communication circuits.

Currently, a digital integrated circuit may include thousands

of million transistors. For such a complicate design, design

method applies the abstraction level concept into the design

flow. According to specific design requirement, proper abstrac-

tion level (or levels) will be used to fulfill the design task. Ac-

cording to the increase order of the abstraction degree, the lev-

els are device, circuit, gate, functional module, and system, as

shown in Figure 1 (Rabaey et al., 2003). For undergraduates

whose major is microelectronics, and have finished merits in

device curriculum, circuit level is the next higher abstraction

level for them to explore. Gate level is the most popular thing

to study for microelectronic undergraduates in the past due to

the standard parts for gates or latches. Modular or systematic

design is studied in other curricula, such as Digital Logic, or

Computer Architecture, since it uses different strategies from

the formers’. With ASICs replaced standard parts, circuit level

design becomes very important in microelectronic industry.

Circuit level design is mostly proprietary to microelectronic

scope, since it needs knowledge of transistors, which will not in

detail be studied for majors other than micro electronics.

On the other hand, a digital integrated circuit can be imple-

mented on a chip sized in several square millimeters, which can

be a central processing system (Lai et al., 2008). For under-

graduate curriculum, they do not need to do such a complex

design that a module, such as adder or multiplier (Purohit et al.,

2009), will fit in their level. For implementation, there are mul-

tiple choices according to which kind of manufacturers you

choose. Nowadays, standard-cell and FPGA (Field Program-

mable Gate Array) based designs are popular due to their ability

to implement efficient design in performance or time-to-market

when compared to other approaches (Fey et al., 1989; Kriete et

al., 1984; Reis, et al., 1988; Nelson, 2008). Specifically, teach-

ers teach standard-cell designs to let students get to know the

manufacturers, and FPGA design to know its design tools ac-

cording to their nature .

This paper is in 4 sections. The 1st part is this introduction.

The 2nd part presents the contents of the curricula. The 3rd part

introduces the project phase of the curriculum. The 4th part is

conclusion.

Contents of the Curriculum

Contents of Textbooks Written by Famous Professors

in the World

With the copyright of those textbooks, some publishing

houses in time pressed textbooks for digital integrated circuits

design in both English and Chinese, such as “Digital Integrated

Circuits—A Design Perspective, 2nd Edition”, and its Chinese

version. Here we use this book in transistor level design, since

it introduces fundamental circuit cells from transistor equations,

which in a way similar to that of an analog integrated circuit

(Rabaey, 2003). Other book, such as “Digital Circuit Analysis

and Design with Simulink Modeling”, introduces digital inte-

grated circuits design from the view of digital logic and CPLD

(Complex Programmable Logic Device) or FPGA (Field Pro-

grammable Gate Array) (Karris, 2007). There are also books

for design flow, such as “Digital Integrated Circuit Design:

From VLSI Architectures to CMOS Fabrication” (Kaeslin,

2008).

Contents of Similar Courses in Other Universities

In University of British Columbia, course of Digital Systems

Design is based on the VHDL Hardware Description Language.

They will show how VHDL can be used to specify very large

systems at the modular or systematic level. And they have a

graduate level course for overview of deep submicron custom

X. CHEN

Figure 1.

Design hierarchy for digital circuit.

IC design, which is based on “physics of semiconductor de-

vices”, and presented in the transistor level (Alon, 2012). In UC

Berkeley, there is a course of Digital Integrated Circuits, which

is “an introduction to digital integrated circuits”. They will look

at various design styles and architectures as well as the issues

that designers must face. The material will cover CMOS de-

vices and manufacturing technology along with CMOS invert-

ers and gates. An advanced course of digital integrated circuits

focuses on the circuit design, optimization, and layout of very

high speed, high density or low power circuits for use in appli-

cations such as microprocessors, signal and multimedia proc-

essors, memory and periphery. “Special attention will devoted

to the most important challenges facing digital circuit designers

today and in the coming decade” (Lemieux & Mehrabadi, 2012).

How to Implement the Design

Since the goal of integrated circuit design is to implement a

microelectronic chip, it is needed to select a way. We select two

popular ways for students’ exercises, which can be found in

Figure 2 (Rabaey et al., 2003).

Analysis of Implementation Approaches

Firstly, concepts of “custom” and “semicustom” should be

taught. In fact, custom design is only used for small parts of the

processing unit with high performance. In other words, custom

design is suitable for a small-to-medium sized integrated circuit.

Commonly, semicustom design is used in large and very large

sized integrated circuit. In reality, a custom design process may

occur for a particular circuit block in the process of a semicus-

tom design.

In semicustom design, computer-aided-design tools are used

for the task. These tools can cover both the “cell-based” and the

“array-based” design. To do a cell-based design, cell libraries

are available in the tool suite. And standard cell or compiled

cell design is in the level of simple logic circuits. While the

macro cell design is usually in the level of modules. To do an

array-based design, things are different. “Pre-diffused” design

and “pre-wired” design are different from manners which they

finish the chip manufacturing processes. The former (“gate

arrays”) finishes the process in the manufacturer’s site after the

design, but the later finishes the process in the designer’s site.

With FPGA’s

With Xilinx design suite, the students may implement a sim-

ple system, such as a controller of traffic light. But this doesn’t

need the students design in the very transistor level, they just

describe the function of a module in HDL (Hardware Descrip-

tion Language), or call an existing one in supporting libraries.

In this way, they already have a chip (FPGA), and they com-

bine function units into what they want. But this way saves

both the time and the money to implement a design.

With Sta ndard Ce lls

With SPICE (the name of a circuit simulator) and corre-

sponding layout editor, such as Virtuoso and Dracula, the stu-

dents can implement a simple circuit such as an 8-bit adder or

an edge-triggered flip-flop, and based which, an 8-bit shift reg-

isters can be built. This is a real transistor level design. And the

result can be taped out for fabrication with a set of design rules

from a specific manufacturer. This way simulates the process in

which large volume products were needed.

Examples of the Results

In order to check the effects of the curriculum, students who

majored in other disciplines during their undergraduate years

are encouraged to attend the class. In result, they are able to do

projects with standard cells in their graduate period (Li, 2012).

X. CHEN

Figure 2.

Implementation methods.

Also, undergraduates of this major are encouraged to do pro-

jects for FPGA design, and finish more steps (such as the “code

coverage”) for the design when compared with their classmates

(Xiong, 2007).

Results

Digital Integrated Circuit Design is a very important part of

microelectronics. In the abstraction hierarchy of the design flow,

we focus on the circuit level to deliver our curriculum for un-

dergraduates in grade four with pre-requisites of device physics.

We choose FPGA and ASIC projects to deliver the post-course

exercises, which will implement the circuits in a real chip.

Students’ performance is excellent. Further focus should be

on the partition of curriculum hours between circuit level de-

sign and higher level design.

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