NTUEE Course by Prof. An-Yeu Wu -...

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© Digital Integrated Circuits2nd Introduction

Digital Integrated Digital Integrated Circuits DesignCircuits Design

IntroductionIntroduction

NTUEE Course

by Prof. An-Yeu Wu

July 30, 2002

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What is this Course all about?What is this Course all about?Introduction to digital integrated circuits.

CMOS devices and manufacturing technology. CMOS inverters and gates. Propagation delay, noise margins, and power dissipation. Sequential circuits. Arithmetic blocksInterconnect, and Memories. Programmable Logic Arrays (PLA)Design methodologies.

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What is this Course all about?What is this Course all about?What will you learn?

Understanding, designing, and optimizing digital circuits with respect to different qualitative/quantitative metrics:

- Cost - Speed - Power dissipation- Reliability

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Course/Textbook OutlineCourse/Textbook OutlineIntroduction: Issues in digital designThe CMOS inverterCombinational logic structuresSequential logic gatesDesign methodologiesInterconnect: R, L and CTimingArithmetic building blocksMemories and array structures

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IntroductionIntroductionThe evolution of digital IC designs: Historical background.

What will be the changes in the future?

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The First ComputerThe First Computer

The BabbageDifference Engine(1832)25,000 partsCost: 17,470 Pounds

in Year 1832

Use Relays as switching components

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ENIAC ENIAC -- The first electronic computer (1946)The first electronic computer (1946)

Use Vacuum Tubes as switching components

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The Transistor RevolutionThe Transistor Revolution

First transistorBell Labs, 1948

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The First Integrated Circuits The First Integrated Circuits

Bipolar logic1960’s

ECL 3-input GateMotorola 1966

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Intel 4004 MicroIntel 4004 Micro--ProcessorProcessor

19711000 transistors1 MHz operation

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Intel Pentium (IV) microprocessorIntel Pentium (IV) microprocessor

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MooreMoore’’s Laws LawIn 1965, Gordon Moore noted that the

number of transistors on a chip doubled every 18 to 24 months.

He made a prediction that semiconductor technology will double its effectiveness every 18~24 months

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MooreMoore’’s Laws Law16151413121110

9876543210

1959

1960

1961

1962

1963

1964

1965

1966

1967

1968

1969

1970

1971

1972

1973

1974

1975

LOG

2 OF

THE

NU

MB

ER O

FC

OM

PON

ENTS

PER

INTE

GR

ATE

D F

UN

CTI

ON

Electronics, April 19, 1965.

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Evolution in ComplexityEvolution in Complexity

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Transistor CountsTransistor Counts

1,000,000

100,000

10,000

1,000

10

100

11975 1980 1985 1990 1995 2000 2005 2010

808680286

i386i486

Pentium®Pentium® Pro

K 1 Billion 1 Billion TransistorsTransistors

Source: IntelSource: Intel

ProjectedProjected

Pentium® IIPentium® III

Courtesy, Intel

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MooreMoore’’s law in Microprocessorss law in Microprocessors

400480088080

8085 8086286

386486 Pentium® proc

P6

0.001

0.01

0.1

1

10

100

1000

1970 1980 1990 2000 2010Year

Tran

sist

ors

(MT)

2X growth in 1.96 years!

Transistors on Lead Microprocessors double every 2 yearsTransistors on Lead Microprocessors double every 2 years

Courtesy, Intel

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Die Size GrowthDie Size Growth

40048008

80808085

8086286

386486 Pentium ® procP6

1

10

100

1970 1980 1990 2000 2010Year

Die

siz

e (m

m)

~7% growth per year~2X growth in 10 years

Die size grows by 14% to satisfy Moore’s LawDie size grows by 14% to satisfy Moore’s Law

Courtesy, Intel

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FrequencyFrequency

P6Pentium ® proc

48638628680868085

8080800840040.1

1

10

100

1000

10000

1970 1980 1990 2000 2010Year

Freq

uenc

y (M

hz)

Lead Microprocessors frequency doubles every 2 yearsLead Microprocessors frequency doubles every 2 years

Doubles every2 years

Courtesy, Intel

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Power DissipationPower DissipationP6

Pentium ® proc

486386

2868086

808580808008

4004

0.1

1

10

100

1971 1974 1978 1985 1992 2000Year

Pow

er (W

atts

)

Lead Microprocessors power continues to increaseLead Microprocessors power continues to increase

Courtesy, Intel

NMOS to CMOS

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Power will be a major problemPower will be a major problem5KW

18KW

1.5KW 500W

4004800880808085

8086286

386486

Pentium® proc

0.1

1

10

100

1000

10000

100000

1971 1974 1978 1985 1992 2000 2004 2008Year

Pow

er (W

atts

)

Power delivery and dissipation will be prohibitivePower delivery and dissipation will be prohibitive

Courtesy, Intel

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Power densityPower density

400480088080

8085

8086

286 386486

Pentium® procP6

1

10

100

1000

10000

1970 1980 1990 2000 2010Year

Pow

er D

ensi

ty (W

/cm

2)

Hot Plate

NuclearReactor

RocketNozzle

Power density too high to keep junctions at low tempPower density too high to keep junctions at low temp

Courtesy, Intel

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Not Only MicroprocessorsNot Only Microprocessors

Digital Cellular Market(Phones Shipped)

1996 1997 1998 1999 2000

Units 48M 86M 162M 260M 435M Analog Baseband

Digital Baseband(DSP + MCU)

PowerManagement

Small Signal RF

PowerRF

(data from Texas Instruments)(data from Texas Instruments)

CellPhone

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Challenges in Digital DesignChallenges in Digital Design

“Microscopic Problems”• Ultra-high speed design• Interconnect• Noise, Crosstalk• Reliability, Manufacturability• Power Dissipation• Clock distribution.

Everything Looks a Little Different

“Macroscopic Issues”• Time-to-Market• Millions of Gates• High-Level Abstractions• Reuse & IP: Portability• Predictability• etc.

…and There’s a Lot of Them!

∝ DSM ∝ 1/DSM

?

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Productivity TrendsProductivity Trends

Source: Sematech

Complexity outpaces design productivity

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

2003

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2005

2007

2009

10

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000Logic Tr./ChipTr./Staff Month.

xxxx

xx

x21%/Yr. compound

Productivity growth rate

x

58%/Yr. compoundedComplexity growth rate

10,000

1,000

100

10

1

0.1

0.01

0.001

Logi

c Tr

ansi

stor

per

Chi

p(M

)

0.01

0.1

1

10

100

1,000

10,000

100,000

Prod

uctiv

ity(K

) Tra

ns./S

taff

-Mo.

Com

plex

ity

Courtesy, ITRS Roadmap

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Why Scaling?Why Scaling?Technology shrinks by 0.7/generation (90nm as now)With every generation can integrate 2x more functions per chip; chip cost does not increase significantlyCost of a function decreases by 2xBut …

How to design chips with more and more functions?Design engineering population does not double every two years…

Hence, a need for more efficient design methodsExploit different levels of abstraction

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Design Abstraction LevelsDesign Abstraction Levels

n+n+S

GD

+

DEVICE

CIRCUIT

GATE

MODULE

SYSTEM

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Design MetricsDesign Metrics

How to evaluate performance of a digital circuit (gate, block, …)?

CostReliabilityScalability (.35um, 0.18um, 90nm, ….)Speed (delay, operating frequency) Power dissipation (Heat Sink)Energy to perform a function (Battery)

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Cost of Integrated CircuitsCost of Integrated Circuits

NRE (non-recurrent engineering) costsDesign time and effort, mask generationOne-time cost factor

Recurrent costsSilicon processing, packaging, testProportional to volumeProportional to chip area

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NRE Cost is IncreasingNRE Cost is Increasing

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Die CostDie Cost

Single die

Wafer

From http://www.amd.com

Going up to 12” (30cm)

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Cost per TransistorCost per Transistor

0.00000010.0000001

0.0000010.000001

0.000010.00001

0.00010.0001

0.0010.001

0.010.01

0.10.111

19821982 19851985 19881988 19911991 19941994 19971997 20002000 20032003 20062006 20092009 20122012

cost: cost: ¢¢--perper--transistortransistor

Fabrication capital cost per transistor (Moore’s law)

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YieldYield%100

per wafer chips ofnumber Totalper wafer chips good of No.)( ×=YieldY

yield Dieper wafer DiescostWafer cost Die×

=

( )area die2

diameterwafer area die

diameter/2wafer per wafer Dies2

××π

−×π

=

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DefectsDefects

α

α

−

×+=

area dieareaunit per defects1yield Die

α is approximately 3

4area) (die cost Die f=

Defects per unit area = 0.5~1 defect/cm2(Manufacturing complexity~mask no.)

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Some Examples (1994)Some Examples (1994)

$4179%402961.5$15000.803Pentium

$27213%482561.6$17000.703Super Sparc

$14919%532341.2$15000.703DEC Alpha

$7327%661961.0$13000.803HP PA 7100

$5328%1151211.3$17000.804Power PC 601

$1254%181811.0$12000.803486 DX2

$471%360431.0$9000.902386DX

Die cost

YieldDies/wafer

Area mm2

Def./ cm2

Wafer cost

Line width

Metal layers

Chip

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ReliabilityReliability――Noise in Digital Integrated CircuitsNoise in Digital Integrated Circuits

i(t)

Inductive coupling Capacitive coupling Power and groundnoise

v(t) VDD

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DC OperationDC OperationVoltage Transfer CharacteristicVoltage Transfer Characteristic

V(x)

V(y)

VOH

VOL

VM

VOHVOL

fV(y)=V(x)

Switching Threshold Voltage

Nominal Voltage Levels

VOH = f(VOL)VOL = f(VOH)VM = f(VM)

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Mapping between analog and digital signalsMapping between analog and digital signals

V IL V IH V in

Slope = -1

Slope = -1

V OL

V OH

Vout

“ 0” VOL

VIL

VIH

VOH

UndefinedRegion

“ 1”

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Definition of Noise MarginsDefinition of Noise Margins

Noise margin high

Noise margin low

VIH

VIL

UndefinedRegion

"1"

"0"

VOH

VOL

NMH

NML

Gate Output Gate Input

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Noise BudgetNoise Budget

Allocates gross noise margin to expected sources of noiseSources: supply noise, cross talk, interference, offsetDifferentiate between fixed and proportional noise sources

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Key Reliability PropertiesKey Reliability PropertiesAbsolute noise margin values are deceptive

A floating node is more easily disturbed than a node driven by a low impedance (in terms of voltage)

Noise immunity is the more important metric –the capability to suppress noise sourcesKey metrics: Noise transfer functions, Output impedance of the driver and input impedance of the receiver;

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Regenerative PropertyRegenerative Property

v0

v1

v3

finv(v)

f (v)

v3

out

v2 in

Regenerative Non-Regenerativev2

v1

f (v)

finv(v)

v3

out

v0 in

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Regenerative PropertyRegenerative Property

A chain of inverters

v0 v1 v2 v3 v4 v5 v6

2

V (V

olt)

4

v0

v1v2

t (nsec)0

2 1

1

3

5

6 8 10Simulated response

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FanFan--in and Fanin and Fan--outout

N

Fan-out N Fan-in M

M

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The Ideal GateThe Ideal Gate

Ri = ∞Ro = 0Fanout = ∞NMH = NML = VDD/2g = ∞

V in

V out

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An OldAn Old--time Invertertime Inverter

NM H

V in (V)

V

o u t

( V )

NM L

V M

0.0

1.0

2.0

3.0

4.0

5.0

1.0 2.0 3.0 4.0 5.0

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Delay DefinitionsDelay Definitions

Vout

tf

tpHL tpLH

trt

Vin

t

90%

10%

50%

50%

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Ring OscillatorRing Oscillator

v0 v1 v5

v1 v2v0 v3 v4 v5

T = 2 ´ tp ´ N

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A FirstA First--Order RC NetworkOrder RC Network

vout

vin C

R

tp = ln (2) τ = 0.69 RC

Important model – matches delay of inverter

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Power DissipationPower Dissipation

Instantaneous power: p(t) = v(t)i(t) = Vsupplyi(t)

Peak power: Ppeak = Vsupplyipeak

Average power:

( )∫ ∫+ +

==Tt

tTt

t supplysupply

ave dttiT

Vdttp

TP )(1

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Energy and EnergyEnergy and Energy--DelayDelay

Power-Delay Product (PDP) =

E = Energy per operation = Pav × tp

Energy-Delay Product (EDP) =

quality metric of gate = E × tp

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A FirstA First--Order RC NetworkOrder RC Network

E0 1→ P t( )dt0

T∫ Vdd isupply t( )dt

0

T∫ Vdd CLdVout

0

Vdd

∫ CL Vdd• 2= = = =

Ecap Pcap t( )dt0

T∫ Vouticap t( )dt

0

T∫ CLVoutdVout

0

Vdd∫

12---C

LVdd•

2= = = =

vout

vin CL

R

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SummarySummaryDigital integrated circuits have come a long way and still have quite some potential left for the coming decadesSome interesting challenges ahead

Getting a clear perspective on the challenges and potential solutions is the purpose of this book

Understanding the design metrics that govern digital design is crucial

Cost, reliability, speed, power and energy dissipation

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