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© Digital Integrated Circuits2nd Introduction
Digital Integrated Digital Integrated CircuitsCircuitsA Design PerspectiveA Design PerspectiveJan M. RabaeyAnantha ChandrakasanBorivoje Nikolic
IntroductionIntroductionJuly 30, 2002
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What is this book all about?What is this book 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, interconnect, and memories. Programmable logic arrays. Design methodologies.
What will you learn?Understanding, designing, and optimizing digital circuits with respect to different quality metrics: cost, speed, power dissipation, and reliability
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Digital Integrated CircuitsDigital Integrated CircuitsIntroduction: Issues in digital designThe CMOS inverterCombinational logic structuresSequential logic gatesDesign methodologiesInterconnect: R, L and CTimingArithmetic building blocksMemories and array structures
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IntroductionIntroduction
Why is designing digital ICs different today than it was before?Will it change in future?
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The First ComputerThe First Computer
The BabbageDifference Engine(1832)25,000 partscost: £17,470
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ENIAC ENIAC -- The first electronic computer (1946)The first electronic computer (1946)
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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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Moore’s LawMoore’s Law
In 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 months
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Moore’s LawMoore’s 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
808680286
i386i486
Pentium®Pentium® Pro
1 Billion 1 Billion TransistorsTransistors
Source: IntelSource: Intel
Pentium® IIPentium® III
K1,000,000
100,000
10,000
1,000
100
10
11975 1980 1985 1990 1995 2000 2005 2010
ProjectedProjected
Courtesy, Intel
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Moore’s law in MicroprocessorsMoore’s law in Microprocessors
400480088080
8085 8086286
386486 Pentium® proc
P6
0.001
0.01
0.1
1
10
100
1000Tr
ansi
stor
s (M
T)
2X growth in 1.96 years!
Transistors on Lead Microprocessors double every 2 yearsTransistors on Lead Microprocessors double every 2 years
1970 1980 1990 2000 2010Year
Courtesy, Intel
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Die Size GrowthDie Size Growth
40048008
80808085
8086286
386486 Pentium ® procP6
10
Die
siz
e (m
m)
~7% growth per year~2X growth in 10 years
100
11970 1980 1990 2000 2010
Year
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
808080084004
Freq
uenc
y (M
hz)
Doubles every2 years
10000
1000
100
10
1
0.11970 1980 1990 2000 2010
Year
Lead Microprocessors frequency doubles every 2 yearsLead Microprocessors frequency doubles every 2 years
Courtesy, Intel
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Power DissipationPower DissipationP6
Pentium ® proc
486386
2868086
808580808008
4004
Pow
er (W
atts
)100
10
1
0.11971 1974 1978 1985 1992 2000
Year
Lead Microprocessors power continues to increaseLead Microprocessors power continues to increase
Courtesy, Intel
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Power will be a major problemPower will be a major problem100000
5KW 18KW
1.5KW 500W
4004800880808085
8086286
386486
Pentium® proc
10000
1
10
100
Pow
er (W
atts
)
1000
0.11971 1974 1978 1985 1992 2000 2004 2008
Year
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
Analog Baseband
Digital Baseband(DSP + MCU)
PowerManagement
Small Signal RF
PowerRF
CellPhone
Digital Cellular Market(Phones Shipped)
1996 1997 1998 1999 2000
Units 48M 86M 162M 260M 435M
(data from Texas Instruments)(data from Texas Instruments)
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Challenges in Digital DesignChallenges in Digital Design
∝ 1/DSM
“Microscopic Problems”• Ultra-high speed design• Interconnect• Noise, Crosstalk• Reliability, Manufacturability• Power Dissipation• Clock distribution.
Everything Looks a Little Different
∝ DSM
?
“Macroscopic Issues”• Time-to-Market• Millions of Gates• High-Level Abstractions• Reuse & IP: Portability• Predictability• etc.
…and There’s a Lot of Them!
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Productivity TrendsProductivity Trends
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
Source: Sematech
Complexity outpaces design productivity
Courtesy, ITRS Roadmap
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Why Scaling?Why Scaling?Technology shrinks by 0.7/generationWith 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, …)?
CostReliabilityScalabilitySpeed (delay, operating frequency) Power dissipationEnergy to perform a function
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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
Going up to 12” (30cm)
From http://www.amd.com
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Cost per TransistorCost per Transistor
Fabrication capital cost per transistor (Moore’s law)
0.00000010.0000001
0.0000010.000001
0.000010.00001
0.00010.0001
0.0010.001
0.010.01
0.10.111
cost: cost: ¢¢--perper--transistortransistor
19821982 19851985 19881988 19911991 19941994 19971997 20002000 20032003 20062006 20092009 20122012
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YieldYield%100
per wafer chips ofnumber Totalper wafer chips good of No.
×=Y
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=
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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
VDDv(t)
i(t)
(a) Inductive coupling (b) Capacitive coupling (c) Power and ground
noise
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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
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
"1"
"0"
VOHVIH
VIL VOL
UndefinedRegion
V(x)
V(y)
VOH
VOL
VIHV
IL
Slope = -1
Slope = -1
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Definition of Noise MarginsDefinition of Noise Margins
NMH
"1"
VOH Noise margin highVIHUndefined
RegionVILNML Noise margin lowVOL
"0"
Gate InputGate Output
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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
in
out out
in
f(v)
finv(v)
finv (v)
f(v)
v3
v1
v2 v0v0 v2
v3
v1
Non-RegenerativeRegenerative
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Regenerative PropertyRegenerative Property
(a) A chain of inverters
v0 v1 v2 v3 v4v5 v6
…
0 2 4 6 8 10t (nsec)
–1
1
3
5
V (V
olt)
v0
v1 v2
(b) Simulated response of chain of MOS inverters
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FanFan--in and Fanin and Fan--outout
N
M
(a) Fan-out N
(b) Fan-in M
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The Ideal GateThe Ideal Gate
Vin
Vout
g=−∞
Ri = ∞
Ro = 0
Fanout = ∞
NMH = NML = VDD/2
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An OldAn Old--time Invertertime Inverter
0.0 1.0 2.0 3.0 4.0 5.0Vin (V)
1.0
2.0
3.0
4.0
5.0V
out (
V)
VMNMH
NML
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Delay DefinitionsDelay Definitions
Vout
t
Vin
50%
tpHL tpLH90%
50%
10% t
trtf
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Ring OscillatorRing Oscillator
v0 v1 v2 v3 v4 v5
v0 v1 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
voutR
vin CL
E0 1→ P t( )dt
0
T
∫ Vdd isupply t( )dt
0
T
∫ Vdd CLdVout0
Vdd
∫ CL Vdd• 2= = = =
Ecap Pcap t( )dt
0
T
∫ Vouticap t( )dt
0
T
∫ CLVoutdVout0
Vdd
∫12---C
LVdd• 2= = = =
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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 course
Understanding the design metrics that govern digital design is crucial
Cost, reliability, speed, power and energy dissipation