systems with digital integrated circuits

Introduction

Sorin Hintea

Basis of Electronics Departament

Systems with Digital Integrated Circuits

Systems with digital integrated circuits - Introduction 2

Commutative logic

The operation of digital circuits is based on the use of switches capable of going through two

distinct states and opposite each other

Ideal switches have zero resistance in ON and infinite in OFF state

In digital circuits are used, electronic switches made with MOS transistors

These transistors are real circuit elements whose ON and OFF resistors are finite

Conductive resistance other than 0 will cause the output response to be delayed

The finite value resistance in the locked state will result in a final drain current through the

blocked switch and therefore undesired power dissipation

Cut-offVG = GND

conductionVG = VDD

MO

S

tran

sist

or ‘0’

‘1’


Proiectarea CID – nivele de abstractizare

Real Circuits Response

vout

vin C

R

tp = ln (2) t = 0.69 RC

Time behavior of digital circuit’s output

Logic switches in real digital integrated circuits are built with MOS transistors

which have an ON resistance of about10 kohms and OFF resistance of about 100

Mohms.

These values are far from the ideal ones and cause power losses and delays of signal

propagation through the circuits


Ideal and real digital circuits

Behaviour of real digital circuits

Blue - ideal input signal; Black –real output signal

0 0.5 1 1.5 2 2.5

x 10-10

-0.5

0

0.5

1

1.5

2

2.5

3

t (sec)

Vo

ut(V

)

tp = 0.69 CL (Reqn+Reqp)/2

Time behavior of digital circuit’s output


Ideal and real digital circuits

Delay in signals propagation - effect of circuit non idealities

Vout

tf

tpHL tpLH

tr

t

V in

t

90%

10%

50%

50%


Digital Circuits Design

First digital integrated circuits

1947 – making the first transistor in the Bell Telephone labs

1949 – first bipolar transistor by Schockley

1958 – first integrated CMOS circuit

1962 – first integrated TTL family circuit (Transistor-

Transistor Logic)

1972 – first 4 bits microprocessor 4004 made by INTEL



First digital integrated circuits

� In the 1970s, mostly nMOS processes were used, cheaper but with high power

consumption

� From the 1980s to today, more and more CMOS processes are being used for their reduced power consumption

[Vadasz69]

© 1969 IEEE.

Intel Museum.

Reprinted with permission.


The Moore’s law

In 1965, Gordon

Moore noted that the

number of transistors on a

chip doubled every 18 to

24 months.

So he predicted that

semiconductor

technology will evolve to

double the number of

transistors every 18

months, which is still true

today

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

195

9

196

0

196

1

196

2

196

3

196

4

196

5

196

6

196

7

196

8

196

9

197

0

197

1

197

2

197

3

197

4

197

5

LO

G2 O

F T

HE

NU

MB

ER

OF

CO

MP

ON

EN

TS

PE

R IN

TE

GR

AT

ED

FU

NC

TIO

N

Electronics, April 19, 1965.


Digital Circuits Evolution

The evolution of the number of chip transistors by 2010

1,000,000

100,000

10,000

1,000

10

100

1

1975 1980 1985 1990 1995 2000 2005 2010

8086

80286i386

i486Pentium®

Pentium® Pro

K1 Billion

Transistors

Source: Intel

Projected

Pentium® II

Pentium® III

Dupa Rabaey, 2005



The evolution of the number of chip transistors by 2010 in

microprocessors industry

Rabaey, 2005

40048008

80808085 8086

286386

486Pentium® proc

P6

0.001

0.01

0.1

1

10

100

1000

1970 1980 1990 2000 2010

Year

Tra

ns

isto

rs (

MT

)

2X growth in 1.96 years!

Transistors on Lead Microprocessors double every 2 years



Evolution of microprocessors working frequency by 2010

Rabaey, 2005

P6

Pentium ® proc486

38628680868085

8080

80084004

0.1

1

10

100

1000

10000

1970 1980 1990 2000 2010

Year

Fre

qu

en

cy (

Mh

z)

Lead Microprocessors frequency doubles every 2 years

Doubles every2 years



Increasing Microprocessors power dissipation until 2000

Rabaey, 2005

P6Pentium ® proc

486

386

2868086

80858080

80084004

0.1

1

10

100

1971 1974 1978 1985 1992 2000

Year

Po

we

r (W

att

s)

Lead Microprocessors power continues to increase



Power consumption will increases to unmanageable values

Rabaey, 2005

5KW 18KW

1.5KW

500W

40048008

80808085

8086286

386486

Pentium® proc

0.1

1

10

100

1000

10000

100000

1971 1974 1978 1985 1992 2000 2004 2008

Year

Po

we

r (W

att

s)

Power delivery and dissipation will be prohibitive



Intel Pentium Processor (IV)



Evaluating the results of a digital circuit design


CMOS technology

How to implement digital integrated circuits :

Single die

Wafer

Going up to 12” (30cm)



Some examples of digital integrated circuit parameters :

Chip Metal layers

Line width

Wafer cost

Def./ cm2

Area mm2

Dies/wafer

Yield Die cost

386DX 2 0.90 $900 1.0 43 360 71% $4

486 DX2 3 0.80 $1200 1.0 81 181 54% $12

Power PC 601

4 0.80 $1700 1.3 121 115 28% $53

HP PA 7100 3 0.80 $1300 1.0 196 66 27% $73

DEC Alpha 3 0.70 $1500 1.2 234 53 19% $149

Super Sparc 3 0.70 $1700 1.6 256 48 13% $272

Pentium 3 0.80 $1500 1.5 296 40 9% $417



Principal design goals

• The design of a CID must follow the highest speed but also the power

consumed

• This is alongside occupying a smaller surface than the implemented circuit

• As a measure of the quality of the switching circuits, the product of the

delay time and the power consumed, a parameter called power-delay

product (PDP)

• In general pentru o anumita tehnologie si o topologie data, PDP este

constant

• In the case of CMOS circuits if the propagation time is to decrease, the

transistors are resized by increasing the width of the channel;

• n this way, the surface of the transistor increases, which leads to the increase

of the current and the power consumed, keeping the PDP constant

Power-Delay Product (PDP) = E = Energy per operation = Pav tp



Evaluating the results of a digital circuit design

Major targets:

� Working speed (delay time, working frequency)

� Power disipation

� Occupied area by a specified circuit

Secondary targets

� Cost

� Reliability

� Scalability

� The energy required to achieve a function



Design abstraction levels in digital circuits

n+n+

S

GD

+

DEVICE

CIRCUIT

GATE

MODULE

SYSTEM



In ce directie evolueaza proiectarea circuitelor digitale VLSI

The technology evolves in the sense of decreasing the size by 0.7 / generation

With each generation you can integrate 2 times more features on the chip; the cost of the chip does not increase significantly

Cost per feature is down 2 times

This has as a consequence a growing number of functions that must be projected by a growing number of human designers

This requires a more efficient design method

Such a method is to increase abstraction levels as well as scalability

Passing from one generation to another is done by applying a constant of all dimensions in the old project

systems with digital integrated circuits

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