Design of Digital
Circuits
EE4143 Design of Digital Circuits
What we will discuss?

Design of digital microelectronic circuits.
» CMOS devices and manufacturing technology.
» Digital gates. Propagation delay, noise margins, and power
dissipation.
» Programmable logic arrays and FPGAs.
» Microelectronic circuits, simulation, verification, and
specification.
» Structural design concepts, design tools.
» VHDL language, data types, objects, operators, control
statements, concurrent statements, functions, and
procedures.
» VHDL modeling techniques, algorithmic, RTL, and gate level
designs.
EE4143 Design of Digital Circuits
What we will discuss?

Design of digital microelectronic circuits.
»
»
»
»

VLSI fabrication process.
Design rules, Design synthesis, Logic design.
Performance estimation, chip engineering.
Emphasis on virtual prototyping, circuit design, optimization,
verification, and testing.
What will you learn?
» Understanding, designing, and optimizing digital circuits with
respect to different quality metrics: cost, speed, power
dissipation, and reliability
» Hardware programming language
» Behavioral and structural design concepts
» Design benchmarking and test.
EE4143 Design of Digital Circuits
Digital Integrated Circuits
What is meant by VLSI?
Brief history of evolution
Today’s Chips
Moore’s Law
Digital circuit applications
Design challenges
Machines Making Machines

EE4143 Design of Digital Circuits
What is a VLSI Circuit?
VERY LARGE SCALE
A circuit that has 10k ~
1Bln transistors on a
single chip
•Still growing as number
of transistors on chip
quadruple every 24
months (Moore’s law!)
INTEGRATED CIRCUIT
Technique where many
circuit components and
the wiring that connects
them are manufactured
simultaneously on a
compact chip (die)
[Adapted from Rabaey’s Digital Integrated Circuits, ©2002, J. Rabaey et al.]
EE4143 Design of Digital Circuits
Brief History
The First Computer: Babbage Difference Engine (1832)
•Executed basic operations
(add, sub, mult, div) in
arbitrary sequences
•Operated in two-cycle
sequence, “Store”, and “Mill”
(execute)
•Included features like
pipelining to make it faster.
•Complexity: 25,000 parts.
•Cost: £17,470 (in 1834!)
EE4143 Design of Digital Circuits
The Electrical Solution
•More cost effective
•Early systems used relays to make simple logic devices
•Still used today in some train safety systems
•The Vacuum Tube
•Originally used for analog processing
•Later, complete digital computers realized
High Point of Tubes: The ENIAC
•18,000 vacuum tubes
•80 ft long, 8.5 ft high, several feet wide
EE4143 Design of Digital Circuits
ENIAC - The first electronic computer
(1946)
EE4143 Design of Digital Circuits
Dawn of the Transistor Age
1947: Bardeen and Brattain
create point-contact transistor
w/two PN junctions. Gain = 18
1951: Shockley develops
junction transistor which can
be manufactured in quantity.
EE4143 Design of Digital Circuits
Early Integration
Jack Kilby, working at Texas Instruments,
invented a monolithic “integrated circuit” in
July 1959.
He had constructed the flip-flop shown in the
patent drawing above.
EE4143 Design of Digital Circuits
Early Integration
In mid 1959, Noyce develops the
first true IC using planar transistors,
•back-to-back pn junctions for
isolation
•diode-isolated silicon resistors and
• SiO2 insulation
• evaporated metal wiring on top
EE4143 Design of Digital Circuits
Practice Makes Perfect
1961: TI and Fairchild introduced
first logic IC’s
(cost ~ $50 in quantity!). This is a
dual flip-flop with 4 transistors.
1963: Densities and yields
improve. This circuit has four
flip-flops.
EE4143 Design of Digital Circuits
Practice Makes Perfect
1967: Fairchild markets the first
semi-custom chip. Transistors
(organized in columns) can be easily
rewired to create different circuits.
Circuit has ~150 logic gates.
1968: Noyce and Moore leave Fairchild to form
Intel. By 1971 Intel had 500 employees;
By 2004, 80,000 employees in 55 countries and
$34.2B in sales.
EE4143 Design of Digital Circuits
The Big Bang
1970: Intel starts
selling a 1k bit
RAM, the 1103.
1971: Ted Hoff at Intel designed the
first microprocessor. The 4004 had
4-bit busses and a clock rate of 108
KHz. It had 2300 transistors and
EE4143 Design of Digital Circuits
was built in a 10 um process.
Exponential Growth
1972: 8080 introduced.
Had 3,500 transistors supporting
a byte-wide data path.
1974: Introduction of the 8088.
Had 6,000 transistors in a 6 um
process. The clock rate was 2 MHz.
EE4143 Design of Digital Circuits
Today
Many disciplines have contributed to the current state of the
art in VLSI Design:
•Solid State Physics
•Materials Science
•Lithography and fab
•Device modeling
To come up with chips like:
EE4143 Design of Digital Circuits
•Circuit design and
layout
•Architecture design
•Algorithms
•CAD tools
Intel Pentium
Intel® Pentium® 4
Intel® Celeron® D
Intel® Pentium® M
Intel® Itanium® 2
Intel® Xeon™
Intel® PCA Cellular
Intel® IXP465 Network
Intel® MXP5800 Digital Media
EE4143 Design of Digital Circuits
Pentium Pro
•Actually a MCM comprising of
microprocessor and L2 cache
Why not make it on
one chip?
EE4143 Design of Digital Circuits
Today
Sun UltraSparc
UltraSPARC IV
UltraSPARC III
UltraSPARC IIIi
UltraSPARC IIi
UltraSPARC IIe
EE4143 Design of Digital Circuits
Pentium 4
» Introduction date: November
20, 2000
– 1.4 GHz clock
– fabricated in 180 nm process,
– 42 mln transistors)
» In 2002 (2 GHz in 130 nm,
55 mln transistors)
» In 2005 (3.8 GHz in 90 nm,
125 mln transistors)
» Typical Use: Desktops and
entry-level workstations
EE4143 Design of Digital Circuits
Supercomputer for Sony's PlayStation
•IBM chip has
nine processor
cores
192 billion
floating-point
operations per
second (192 G)
Typical Use:
multimedia
•
•
EE4143 Design of Digital Circuits
3
Intel Core 2 Microprocessor
•In 2006
•143 mm2
•3 GHZ operation
•65 nm CMOS
technology
291 mln transistors
•
EE4143 Design of Digital Circuits
Other chips
IDT R5000
IBM Power PC 601
EE4143 Design of Digital
Circuits
from
http://micro.magnet.fsu.edu/chipshots/index.html
Other chips
cyrix_math_coprocessor_83S87
Fairchild Clipper C100
EE4143 Design of Digital
Circuits
from
http://micro.magnet.fsu.edu/chipshots/index.html
Other chips
Fujitsu 68903
HP PA8000
EE4143 Design of Digital
Circuits
from
http://micro.magnet.fsu.edu/chipshots/index.html
Other chips
Motorola MC68020
IBM/Motorola Power PC620
EE4143 Design of Digital
Circuits
from
http://micro.magnet.fsu.edu/chipshots/index.html
Evolution of Electronics
EE4143 Design of Digital Circuits
Moore’s Law
In
1965, Gordon Moore noted that the
number of transistors on a chip doubled
every 12 months.
He made a prediction that
semiconductor technology will double its
effectiveness every 18 months
EE4143 Design of Digital Circuits
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
LOG2 OF THE NUMBER OF
COMPONENTS PER INTEGRATED FUNCTION
Moore’s Law
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Electronics, April 19, 1965.
EE4143 Design of Digital Circuits
Technology Directions: SIA
Roadmap
Year
1999 2002 2005 2008 2011 2014
Feature size (nm)
180
130 100
70
50
35
2
Logic trans/cm
6.2M 18M 39M 84M 180M 390M
Cost/trans (mc)
1.735 .580 .255 .110 .049 .022
#pads/chip
1867 2553 3492 4776 6532 8935
Clock (MHz)
1250 2100 3500 6000 10000 16900
2
Chip size (mm )
340
430 520 620
750
900
Wiring levels
6-7
7
7-8
8-9
9
10
Power supply (V)
1.8
1.5
1.2
0.9
0.6
0.5
High-perf pow (W)
90
130 160 170
175
183
EE4143 Design of Digital Circuits
Technology Directions:
transistor feature sizes
log2 of lambda in nm
15
10
5
0
1970
1980
EE4143 Design of Digital Circuits
1990
2000
time in years
2010
2020
Evolution in Complexity
EE4143 Design of Digital Circuits
Transistor Counts
K
1,000,000
100,000
10,000
1,000
100
10
Source: Intel
1
1970 1975 1980 1985 1990 1995 2000 2005
Projected
EE4143 Design of Digital Circuits
Courtesy, Intel
Moore’s law in Microprocessors
Transistors (MT)
1000
2X growth in 1.96 years!
100
10
486
1
386
286
0.1
0.01
P6
Pentium® proc
8086
8080
8008
4004
8085
0.001
1970
1980
1990
Year
2000
2010
Transistors on Lead Microprocessors double every 2 years
EE4143 Design of Digital Circuits
Courtesy, Intel
Die Size Growth
Die size (mm)
100
10
8080
8008
4004
1
1970
8086
8085
1980
286
386
P6
Pentium
® proc
486
~7% growth per year
~2X growth in 10 years
1990
Year
2000
2010
Die size grows by 14% to satisfy Moore’s Law
EE4143 Design of Digital Circuits
Courtesy, Intel
Frequency
CMOS
nMOS
Lead Microprocessors frequency doubles every 2 years
EE4143 Design of Digital Circuits
Courtesy, Intel
Power dissipation warning in 2000
100000
18KW
5KW
1.5KW
500W
Power (Watts)
10000
1000
Pentium® proc
100
286 486
8086
10
386
8085
8080
8008
1 4004
0.1
1971 1974 1978 1985 1992 2000 2004 2008
Year
Did this really happen?
EE4143 Design of Digital Circuits
Courtesy, Intel
Power Dissipation
Lead Microprocessors power increase
EE4143 Design of Digital Circuits
Courtesy, Intel
Power density
Power Density (W/cm2)
10000
1000
100
Rocket
Nozzle
Nuclear
Reactor
8086
10 4004
Hot Plate
P6
8008 8085
Pentium® proc
386
286
486
8080
1
1970
1980
1990
2000
2010
Year
Power density too high to keep junctions at low temp
EE4143 Design of Digital Circuits
Courtesy, Intel
Not Only Microprocessors
Cell
Phones
Video games
Small
Signal RF
Power
RF
Power
Management
Units
Digital Cellular Market
(Phones Shipped)
1996 1997 1998 1999 2000
48M 86M 162M 260M 435M
Analog
Baseband
Digital Baseband
(DSP + MCU)
iPod
EE4143 Design of Digital Circuits
iTablet
Challenges in Digital Design
“Microscopic Problems”
• Ultra-high speed design
• Interconnect
• Noise, Crosstalk
• Reliability, Manufacturability
• Power Dissipation
• Clock distribution.
Everything Looks a Little Different
EE4143 Design of Digital Circuits
“Macroscopic Issues”
• Time-to-Market
• Millions of Gates
• High-Level Abstractions
• Reuse & IP: Portability
• Predictability
• etc.
…and There’s a Lot of Them!
10,000
10,000,000
100,000
100,000,000
Logic Tr./Chip
Tr./Staff Month.
1,000
1,000,000
10,000
10,000,000
100
100,000
Productivity
(K) Trans./Staff - Mo.
Complexity
Logic Transistor per Chip (M)
Productivity Trends
1,000
1,000,000
58%/Yr. compounded
Complexity growth rate
10
10,000
100
100,000
1,0001
10
10,000
x
0.1
100
xx
0.01
10
xx
x
1
1,000
21%/Yr. compound
Productivity growth rate
x
x
0.1
100
0.01
10
2009
2007
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
1983
1981
0.001
1
Source: Sematech
Complexity outpaces design productivity
EE4143 Design of Digital Circuits
Courtesy, ITRS Roadmap
Definitions




Wafer – a thin circular silicon
Each wafer holds hundreds of dies
Transistors and wiring are made from many layers (usually 10 – 15)
built on top of one another
» the first half-dozen or so layers define transistors
» the second define the metal wires between transistors
Lambda () – the smallest resolvable feature size imprinted on the IC;
it is roughly half the length of the smallest transistor
» 0.2m IC – the smallest transistors are
approximately 0.2m in length (= 0.1m)
EE4143 Design of Digital Circuits
Why Scaling?




Technology shrinks by 0.7/generation
With every generation can integrate 2x more
functions per chip for about the same $/chip
Cost of a function decreases by 2x
But …
» 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 methods
» Exploit different levels of abstraction
EE4143 Design of Digital Circuits
Design Flow
EE4143 Design of Digital Circuits
Design Abstraction Levels
SYSTEM
MODULE
+
GATE
CIRCUIT
DEVICE
G
S
n+
EE4143 Design of Digital Circuits
D
n+