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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Introduction to Digital CMOS Technology
...Or What We Do with 1s and 0s...
Anurup Mitra
STMicroelectronics Pvt. Ltd.
March 2012
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Modern Day Integrated Systems
Why Not Just One?
Why do we not stick to just one - either analog or digital -for all our signal processing needs?
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Modern Day Integrated Systems
Why Not Just One?
Why do we not stick to just one - either analog or digital -for all our signal processing needs?
Naturally occurring signals are analog - which is why we
need to extensively use A/D and D/A interfaces.
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Modern Day Integrated Systems
Why Not Just One?
Why do we not stick to just one - either analog or digital -for all our signal processing needs?
Naturally occurring signals are analog - which is why we
need to extensively use A/D and D/A interfaces.
Digital circuits are more robust to environmental and devicenoise.
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Modern Day Integrated Systems
Why Not Just One?
Why do we not stick to just one - either analog or digital -for all our signal processing needs?
Naturally occurring signals are analog - which is why we
need to extensively use A/D and D/A interfaces.
Digital circuits are more robust to environmental and devicenoise.
Today 5-10% of all signal processing chip circuitry is analogand the rest is digital. From the 1980s there has been arapid shift of signal processing tasks to digital circuitryrather than analog.
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN)
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem)
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless Cellular Telephony (GSM, CDMA)
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless Cellular Telephony (GSM, CDMA) WLAN (Bluetooth, UWB, 802.11 a/b/g)
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless Cellular Telephony (GSM, CDMA) WLAN (Bluetooth, UWB, 802.11 a/b/g) Radio
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless Cellular Telephony (GSM, CDMA) WLAN (Bluetooth, UWB, 802.11 a/b/g) Radio
Computing and Control
I d i
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless Cellular Telephony (GSM, CDMA) WLAN (Bluetooth, UWB, 802.11 a/b/g) Radio
Computing and Control Storage (disk drives, digital tape)
I t d ti t
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless Cellular Telephony (GSM, CDMA) WLAN (Bluetooth, UWB, 802.11 a/b/g) Radio
Computing and Control Storage (disk drives, digital tape) Imagers and Displays (CMOS, CCDs, TFT, LCD)
Introduction tof S C
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless Cellular Telephony (GSM, CDMA) WLAN (Bluetooth, UWB, 802.11 a/b/g) Radio
Computing and Control Storage (disk drives, digital tape) Imagers and Displays (CMOS, CCDs, TFT, LCD)
Instrumentation (Test equipment, sensors)
Introduction toA li i f Mi d Si l IC
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless
Cellular Telephony (GSM, CDMA) WLAN (Bluetooth, UWB, 802.11 a/b/g) Radio
Computing and Control Storage (disk drives, digital tape) Imagers and Displays (CMOS, CCDs, TFT, LCD)
Instrumentation (Test equipment, sensors)
Consumer Electronics (You tell me!)
Introduction toA li i f Mi d Si l IC
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Application of Mixed Signal ICs
Communications Wireline
Telephone (DSL,ISDN) Television (TV tuner, cable modem) Ethernet (Gigabit, 10/100Mbps)
Wireless
Cellular Telephony (GSM, CDMA) WLAN (Bluetooth, UWB, 802.11 a/b/g) Radio
Computing and Control Storage (disk drives, digital tape)
Imagers and Displays (CMOS, CCDs, TFT, LCD) Instrumentation (Test equipment, sensors)
Consumer Electronics (You tell me!)
Introduction toQ i k O i f T d
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Introduction toDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Quick Overview of Trends
Reduced cost is one of the big attractions of integrated
electronics, and the cost advantage continues to increase asthe technology evolves toward the production of larger andlarger circuit functions on a single semiconductor substrate.
Introduction toQ i k O i f T d
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uDigital CMOS
Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Quick Overview of Trends
Reduced cost is one of the big attractions of integrated
electronics, and the cost advantage continues to increase asthe technology evolves toward the production of larger andlarger circuit functions on a single semiconductor substrate.
For simple circuits, the cost per component is nearlyinversely proportional to the number of components, the
result of the equivalent piece of semiconductor in theequivalent package containing more components.
Introduction toQ ick O e ie of T e ds
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Quick Overview of Trends
Reduced cost is one of the big attractions of integrated
electronics, and the cost advantage continues to increase asthe technology evolves toward the production of larger andlarger circuit functions on a single semiconductor substrate.
For simple circuits, the cost per component is nearlyinversely proportional to the number of components, the
result of the equivalent piece of semiconductor in theequivalent package containing more components.
But as components are added, decreased yields more thancompensate for the increased complexity, tending to raisethe cost per component.
Introduction toQuick Overview of Trends
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Quick Overview of Trends
Reduced cost is one of the big attractions of integrated
electronics, and the cost advantage continues to increase asthe technology evolves toward the production of larger andlarger circuit functions on a single semiconductor substrate.
For simple circuits, the cost per component is nearlyinversely proportional to the number of components, the
result of the equivalent piece of semiconductor in theequivalent package containing more components.
But as components are added, decreased yields more thancompensate for the increased complexity, tending to raisethe cost per component.
Thus there is a minimum cost at any given time in theevolution of the technology.
Introduction toMoores Law
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Moore s Law
Moores ObservationThe complexity for minimum component costs has increasedat a rate of roughly a factor of two per year. Certainly overthe short term this rate can be expected to continue, if notto increase. Over the longer term, the rate of increase is a
bit more uncertain, although there is no reason to believe itwill not remain nearly constant for at least 10 years. Thatmeans by 1975, the number of components per integratedcircuit for minimum cost will be 65,000.
I believe that such a large circuit can be built on a singlewafer.
There are corollaries to this Observation/Law.
Introduction toD l CMOSBenefits to Digital Technology
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Benefits to Digital Technology
Enhanced functionality and flexibility
Introduction toDi i l CMOSBenefits to Digital Technology
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Benefits to Digital Technology
Enhanced functionality and flexibility
Automated design and test possible
Introduction toDi it l CMOSBenefits to Digital Technology
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Benefits to Digital Technology
Enhanced functionality and flexibility
Automated design and test possible
Arbitrary precision possible (at least in theory)
Introduction toDigital CMOSBenefits to Digital Technology
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Benefits to Digital Technology
Enhanced functionality and flexibility
Automated design and test possible
Arbitrary precision possible (at least in theory)
Provides inexpensive storage capability
Introduction toDigital CMOSDual Power Supplies for Analog and Digital
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Dual Power Supplies for Analog and Digital
Due to conflicting needs for analog and digital circuits,today a separate power supply is used for the analog anddigital blocks on a mixed signal chip.
Introduction toDigital CMOSDual Power Supplies for Analog and Digital
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Dual Power Supplies for Analog and Digital
Due to conflicting needs for analog and digital circuits,today a separate power supply is used for the analog anddigital blocks on a mixed signal chip.
In the O-Lab we have design kits from both TSMC and
UMC for 180nm.
Introduction toDigital CMOSDual Power Supplies for Analog and Digital
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Digital CMOSTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
Dual Power Supplies for Analog and Digital
Due to conflicting needs for analog and digital circuits,today a separate power supply is used for the analog anddigital blocks on a mixed signal chip.
In the O-Lab we have design kits from both TSMC and
UMC for 180nm.
These have separate transistors for analog and digitalfunctions. The analog transistors are operated from a supplyvoltage of 2.5V and have a minimum feature size of 0.25
m, while the digital devices are operated at 1.8V and havea minimum feature size of 0.18 m.
Introduction toDigital CMOSITRS
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gTechnology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in Digital
ICs
ITRS is the International Technology Roadmap forSemiconductors. The organisation is responsible for layingout milestones for the entire semiconductor industry.
Introduction toDigital CMOSITRS
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
ITRS is the International Technology Roadmap forSemiconductors. The organisation is responsible for layingout milestones for the entire semiconductor industry.
Year of Production 2005 2006 2007 2008 2009 2010 2011 2012 2013Digital
Supply voltage (V) 1.2 1.2 1.2 1.2 1.1 1.1 1.1 1 1Tox (nm) 2.2 2.1 2.0 1.9 1.6 1.5 1.4 1.4 1.3
Gate Length (nm) 75 65 53 45 37 32 28 25 22gm/gds at 5Lmindigital 47 40 32 30 30 30 30 30 30
Peak Ft (GHz) 120 140 170 200 240 280 320 360 400Analog
Supply voltage (V) 2.5 2.5 2.5 2.5 2.5 1.8 1.8 1.8 1.8Tox (nm) 5 5 5 5 5 3 3 3 3
Gate Length (nm) 250 250 250 250 250 180 180 180 180gm/gds at 10Lmindigital 220 220 220 220 220 160 160 160 160
Peak Ft (GHz) 40 40 40 40 40 50 50 50 50
Introduction toDigital CMOSSemiconductor Rankings for 2011
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
g
Introduction toDigital CMOSWhy Digital?
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
y g
It has been often stated that digital circuits are used over
analog ones because of their noise margin.
Introduction toDigital CMOS
T h lWhy Digital?
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
It has been often stated that digital circuits are used over
analog ones because of their noise margin.The noise margin of digital circuits is something that isinherent in their construction and functionality. While analogdesigners take great pains to lower the noise present in their
circuits, digital designers choose a circuit methodologywhere their is no noise!
Introduction toDigital CMOS
T h lWhy Digital?
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
It has been often stated that digital circuits are used over
analog ones because of their noise margin.The noise margin of digital circuits is something that isinherent in their construction and functionality. While analogdesigners take great pains to lower the noise present in their
circuits, digital designers choose a circuit methodologywhere their is no noise!
Digital electronics works at a level of abstraction muchabove voltages and currents. It collapses the values that canbe taken by a variable to 2 - namely 1 and 0. In laymans
language, it can be said, that digital is bothered aboutwhether a certain parameter is present or absent - and notabout how much is present or absent.
Introduction toDigital CMOS
TechnologyThe Digital Abstraction
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Electronics has always sought to process or transmitinformation.
Introduction toDigital CMOS
TechnologyThe Digital Abstraction
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Electronics has always sought to process or transmitinformation.
Scheme 1 To transmit information, a given voltage issplit up into equal divisions, each onesignifying a particular code. For example tocode the English alphabet, there need to be 26equal divisions for a given voltage.
Introduction toDigital CMOS
TechnologyThe Digital Abstraction
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Electronics has always sought to process or transmitinformation.
Scheme 1 To transmit information, a given voltage issplit up into equal divisions, each onesignifying a particular code. For example tocode the English alphabet, there need to be 26equal divisions for a given voltage. Any
amount of intrinsic or external noise canchange the coded representation.
Introduction toDigital CMOS
TechnologyThe Digital Abstraction
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Technology
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Electronics has always sought to process or transmitinformation.
Scheme 1 To transmit information, a given voltage issplit up into equal divisions, each onesignifying a particular code. For example tocode the English alphabet, there need to be 26equal divisions for a given voltage. Any
amount of intrinsic or external noise canchange the coded representation.
Scheme 2 In transmitting information at each point intime, only one of two codes can be valid - 1 or0 - also called bits. The English alphabet canbe represented by having a sequence of 5 bitsfor each letter.
Introduction toDigital CMOS
TechnologyThe Digital Abstraction
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gy
Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Electronics has always sought to process or transmitinformation.
Scheme 1 To transmit information, a given voltage issplit up into equal divisions, each onesignifying a particular code. For example tocode the English alphabet, there need to be 26equal divisions for a given voltage. Any
amount of intrinsic or external noise canchange the coded representation.
Scheme 2 In transmitting information at each point intime, only one of two codes can be valid - 1 or0 - also called bits. The English alphabet canbe represented by having a sequence of 5 bitsfor each letter. The time and/or hardwareincreases, but the coding is more robustagainst noise.
Introduction toDigital CMOS
TechnologyThe Digital Abstraction
El i h l h i
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Electronics has always sought to process or transmitinformation.
Scheme 1 To transmit information, a given voltage issplit up into equal divisions, each onesignifying a particular code. For example tocode the English alphabet, there need to be 26equal divisions for a given voltage. Any
amount of intrinsic or external noise canchange the coded representation.
Scheme 2 In transmitting information at each point intime, only one of two codes can be valid - 1 or0 - also called bits. The English alphabet canbe represented by having a sequence of 5 bitsfor each letter. The time and/or hardwareincreases, but the coding is more robustagainst noise.
Scheme 2 is the digital abstraction.
Introduction toDigital CMOS
TechnologyGenerating 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
The first requirement of digital electronics is a circuit that is
capable of generating only two output levels - 1 and 0.
Introduction toDigital CMOS
TechnologyGenerating 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
The first requirement of digital electronics is a circuit that is
capable of generating only two output levels - 1 and 0.Because, in real life we do not have a 1 and a 0, we seekthe digital abstraction from real life parameters by settingthe maximum voltage available in a circuit to 1 and theminimum to 0.
Introduction toDigital CMOS
TechnologyGenerating 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
The first requirement of digital electronics is a circuit that is
capable of generating only two output levels - 1 and 0.Because, in real life we do not have a 1 and a 0, we seekthe digital abstraction from real life parameters by settingthe maximum voltage available in a circuit to 1 and theminimum to 0.
Therefore, to represent these output levels, there needs to bea circuit which can at any time, connect to either VDD orground.
Introduction toDigital CMOS
TechnologyGenerating 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
The first requirement of digital electronics is a circuit that is
capable of generating only two output levels - 1 and 0.Because, in real life we do not have a 1 and a 0, we seekthe digital abstraction from real life parameters by settingthe maximum voltage available in a circuit to 1 and theminimum to 0.
Therefore, to represent these output levels, there needs to bea circuit which can at any time, connect to either VDD orground. A simple implementation would be to have afloating node that could be connected by an (electrically
controlled) switch to either supply or ground.
Introduction toDigital CMOS
TechnologyGenerating 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
The first requirement of digital electronics is a circuit that is
capable of generating only two output levels - 1 and 0.Because, in real life we do not have a 1 and a 0, we seekthe digital abstraction from real life parameters by settingthe maximum voltage available in a circuit to 1 and theminimum to 0.
Therefore, to represent these output levels, there needs to bea circuit which can at any time, connect to either VDD orground. A simple implementation would be to have afloating node that could be connected by an (electrically
controlled) switch to either supply or ground.In IC technology, an electrically operated switch is easilyobtained by an MOS transistor.
Introduction toDigital CMOS
TechnologyDetecting 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Detecting a 1 and a 0 implies having an output from a
system that can respond to these two stiumli.
Introduction toDigital CMOS
TechnologyDetecting 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Detecting a 1 and a 0 implies having an output from a
system that can respond to these two stiumli.
The inputs and outputs can be mapped in two unique ways:
Buffer 0 0; 1 1
Introduction toDigital CMOS
TechnologyDetecting 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Detecting a 1 and a 0 implies having an output from a
system that can respond to these two stiumli.
The inputs and outputs can be mapped in two unique ways:
Buffer 0 0; 1 1
Inverter 0 1; 1 0
Introduction toDigital CMOS
TechnologyDetecting 1s and 0s
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Anurup Mitra
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Detecting a 1 and a 0 implies having an output from a
system that can respond to these two stiumli.
The inputs and outputs can be mapped in two unique ways:
Buffer 0 0; 1 1
Inverter 0 1; 1 0
The second option is easier to implement with electronics.
Introduction toDigital CMOS
TechnologyDetecting 1s and 0s
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Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Detecting a 1 and a 0 implies having an output from a
system that can respond to these two stiumli.
The inputs and outputs can be mapped in two unique ways:
Buffer 0 0; 1 1
Inverter 0 1; 1 0
The second option is easier to implement with electronics.
An inverter is used as a basic building block of all digitalcircuits because of its innate ability to both detect andgenerate a 1 and a 0 successfully.
Introduction toDigital CMOS
TechnologyThe CMOS Digital Inverter
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The MOSFETs act as electrically (voltage) controlledswitches. Two of the reasons CMOS technology caught thedigital designers fancy were the MOSFETs extremely highresistance in the OFF state and its extremely low resistancein the ON.
Introduction toDigital CMOS
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A Mi
The CMOS Digital Inverter
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The MOSFETs act as electrically (voltage) controlledswitches. Two of the reasons CMOS technology caught thedigital designers fancy were the MOSFETs extremely highresistance in the OFF state and its extremely low resistancein the ON.
By employing one nMOS and one pMOS switch, the state ofthe two switches is always complementary - hence the name
CMOS digital electronics.
Introduction toDigital CMOS
Technology
A Mit
Digital Performance Measures
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Unlike analog circuits, digital circuits are quantified bylargely two performance measures - speed and power.These two directly trade off with each other.
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Technology
Anurup Mitra
Digital Performance Measures
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Unlike analog circuits, digital circuits are quantified bylargely two performance measures - speed and power.These two directly trade off with each other.
An inverter works by charging a node to a 1 or by
discharging it to a 0. Since all nodes in an MOS circuit arecapacitive in nature, the charging or discharging is madefaster by using a higher current, thus providing a greaterspeed of operation.
Introduction toDigital CMOS
Technology
Anurup Mitra
Digital Performance Measures
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Introduction
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Issues in DigitalICs
Unlike analog circuits, digital circuits are quantified bylargely two performance measures - speed and power.These two directly trade off with each other.
An inverter works by charging a node to a 1 or by
discharging it to a 0. Since all nodes in an MOS circuit arecapacitive in nature, the charging or discharging is madefaster by using a higher current, thus providing a greaterspeed of operation.
However, the higher current also implies a greater power
dissipation.
Introduction toDigital CMOS
Technology
Anurup Mitra
The Truth About Digital
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It can be safely said that all of digital electronics containsthe gainful employment of inverters of various shapes andsizes cascaded in a fashion to provide a meaningful output toa given set of inputs.
Introduction toDigital CMOS
Technology
Anurup Mitra
The Truth About Digital
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Introduction
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It can be safely said that all of digital electronics containsthe gainful employment of inverters of various shapes and
sizes cascaded in a fashion to provide a meaningful output toa given set of inputs.
A given stage of a digital circuit, no matter how seeminglycomplex can be simplified to an equivalent inverter.
Introduction toDigital CMOS
Technology
Anurup Mitra
The Truth About Digital
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p
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
It can be safely said that all of digital electronics containsthe gainful employment of inverters of various shapes and
sizes cascaded in a fashion to provide a meaningful output toa given set of inputs.
A given stage of a digital circuit, no matter how seeminglycomplex can be simplified to an equivalent inverter.
Therefore, if the static characteristics of a digital invertercan be studied, the static characteristics of any equivalentinverter can be known. The static characteristics of aninverter is the steady state response of an inverter - this isusually just the transfer function of the same.
Introduction toDigital CMOS
Technology
Anurup Mitra
The Truth About Digital
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p
Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
It can be safely said that all of digital electronics containsthe gainful employment of inverters of various shapes and
sizes cascaded in a fashion to provide a meaningful output toa given set of inputs.
A given stage of a digital circuit, no matter how seeminglycomplex can be simplified to an equivalent inverter.
Therefore, if the static characteristics of a digital invertercan be studied, the static characteristics of any equivalentinverter can be known. The static characteristics of aninverter is the steady state response of an inverter - this isusually just the transfer function of the same.
Similarly, the dynamic characteristics of the digital inverter -the behaviour of the inverter in time, i.e., how fast it reachessteady state - should be comprehended.
Introduction toDigital CMOS
Technology
Anurup Mitra
Abstraction
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Digital circuits employ the concept of abstraction. This
implies that a circuit is split up into a hierarchy and eachlevel of the hierarchy constitute one abstraction. Forexample at the lowest level there is the inverter, then logicgates, followed by functional blocks and so on.
Introduction toDigital CMOS
Technology
Anurup Mitra
Abstraction
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PerformanceMetrics
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Digital circuits employ the concept of abstraction. This
implies that a circuit is split up into a hierarchy and eachlevel of the hierarchy constitute one abstraction. Forexample at the lowest level there is the inverter, then logicgates, followed by functional blocks and so on.
The performance of each level in terms of speed and powercan be characterised and used in the next higher level ofhierarchy.
Introduction toDigital CMOS
Technology
Anurup Mitra
Abstraction
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Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Digital circuits employ the concept of abstraction. This
implies that a circuit is split up into a hierarchy and eachlevel of the hierarchy constitute one abstraction. Forexample at the lowest level there is the inverter, then logicgates, followed by functional blocks and so on.
The performance of each level in terms of speed and powercan be characterised and used in the next higher level ofhierarchy.
This abstraction also allows the use of design automation.
CAD or EDA tools can take in as input the design specs ofthe top level of the hierarchy and produce as output, GDS IIformat - ready for tape-out.
Introduction toDigital CMOS
Technology
Anurup Mitra
Abstraction
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Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
Digital circuits employ the concept of abstraction. This
implies that a circuit is split up into a hierarchy and eachlevel of the hierarchy constitute one abstraction. Forexample at the lowest level there is the inverter, then logicgates, followed by functional blocks and so on.
The performance of each level in terms of speed and powercan be characterised and used in the next higher level ofhierarchy.
This abstraction also allows the use of design automation.
CAD or EDA tools can take in as input the design specs ofthe top level of the hierarchy and produce as output, GDS IIformat - ready for tape-out. This is known as synthesis.
Introduction toDigital CMOS
Technology
Anurup Mitra
CAD Tools
As has been mentioned earlier CAD tools play an
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p yindispensable part in the manufacture of digital ICs.Todays digital ICs pack so much functionality into a smallarea, the number of transistors required for implementationcannot be hand placed and routed.
Introduction toDigital CMOS
Technology
Anurup Mitra
CAD Tools
As has been mentioned earlier CAD tools play an
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PerformanceMetrics
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p yindispensable part in the manufacture of digital ICs.Todays digital ICs pack so much functionality into a smallarea, the number of transistors required for implementationcannot be hand placed and routed.
A digital synthesis tool takes a top level description andseeks to create the actual circuit by looking up a
pre-manufactured library. From the library it selectscharacterised components in a manner such that the toplevel design specs can be met.
Introduction toDigital CMOS
Technology
Anurup Mitra
CAD Tools
As has been mentioned earlier CAD tools play an
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Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
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indispensable part in the manufacture of digital ICs.Todays digital ICs pack so much functionality into a smallarea, the number of transistors required for implementationcannot be hand placed and routed.
A digital synthesis tool takes a top level description andseeks to create the actual circuit by looking up a
pre-manufactured library. From the library it selectscharacterised components in a manner such that the toplevel design specs can be met.
There are many variations on this theme. The standard celland the FPGA are the most widely used. While a standardcell library contains different versions of each functionalblock on software, the FPGA has pre-fabricated functionalblocks the interconnections between which can be(re)programmed.
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Anurup Mitra
Interconnect and Power Issues
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While the abstraction works well for digital circuits, inmodern day deep-submicron design interconnect issues oftentend to break this down.
Introduction toDigital CMOS
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Anurup Mitra
Interconnect and Power Issues
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While the abstraction works well for digital circuits, inmodern day deep-submicron design interconnect issues oftentend to break this down.
While digital ciruits tend to be characterised and used byCAD tools in terms of their intrinsic delays (i.e. the delaysincurred in charging/discharging an output to 1/0 as a
response to an input), the interconnects themselvescontribute parasitic capacitances and resistances thatincrease the overall delay of the system.
Introduction toDigital CMOS
Technology
Anurup Mitra
Interconnect and Power Issues
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Introduction
Basic BuildingBlock
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
While the abstraction works well for digital circuits, inmodern day deep-submicron design interconnect issues oftentend to break this down.
While digital ciruits tend to be characterised and used byCAD tools in terms of their intrinsic delays (i.e. the delaysincurred in charging/discharging an output to 1/0 as a
response to an input), the interconnects themselvescontribute parasitic capacitances and resistances thatincrease the overall delay of the system.
As aggressive scaling continues, the power issue has limited
integration with each passing digital generation. There is alimit to the amount of localised heat generation that can behandled by a packaged integrated circuit.
Introduction toDigital CMOS
Technology
Anurup Mitra
Timing and Synchronisation Issues
The most widely permeated digital circuit is the
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Block
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The most widely permeated digital circuit is themicroprocessor. Most of the components of the
microprocessor are synchronised to operate on a rising or afalling clock edge.
Introduction toDigital CMOS
Technology
Anurup Mitra
Timing and Synchronisation Issues
The most widely permeated digital circuit is the
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Introduction
Basic Building
Block
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
The most widely permeated digital circuit is themicroprocessor. Most of the components of the
microprocessor are synchronised to operate on a rising or afalling clock edge.
The main clock is derived from a crystal oscillator by a PLL.This clock needs to be distributed to all parts of the chip forproper synchronisation of all functional blocks.
Introduction toDigital CMOS
Technology
Anurup Mitra
Timing and Synchronisation Issues
The most widely permeated digital circuit is the
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Introduction
Basic Building
Block
PerformanceMetrics
Digital Philosophy
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The most widely permeated digital circuit is themicroprocessor. Most of the components of the
microprocessor are synchronised to operate on a rising or afalling clock edge.
The main clock is derived from a crystal oscillator by a PLL.This clock needs to be distributed to all parts of the chip forproper synchronisation of all functional blocks.
However, the clock signal experiences different delays as ittravels to different parts of the chip. This gives rise to clockskews and possible race conditions.
Introduction toDigital CMOS
Technology
Anurup Mitra
Timing and Synchronisation Issues
The most widely permeated digital circuit is the
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Introduction
Basic Building
Block
PerformanceMetrics
Digital Philosophy
Issues in DigitalICs
The most widely permeated digital circuit is themicroprocessor. Most of the components of the
microprocessor are synchronised to operate on a rising or afalling clock edge.
The main clock is derived from a crystal oscillator by a PLL.This clock needs to be distributed to all parts of the chip for
proper synchronisation of all functional blocks.
However, the clock signal experiences different delays as ittravels to different parts of the chip. This gives rise to clockskews and possible race conditions.
Clock distribution trees, which symmetrically distribute theclock to various parts of the chip need to be employed.
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