CMOS Voltage References: An Analytical and Practical Perspective

300 Pages·2013·5.372 MB·English

by  Chi?Wah Kok, Wing?Shan Tam(auth.)

CMOS VOLTAGE
REFERENCES
CMOS VOLTAGE
REFERENCES
AN ANALYTICAL AND PRACTICAL
PERSPECTIVE
Chi-WahKokandWing-ShanTam
CanaanMicroelectronicsCorporationLtd,HongKong
Thiseditionfirstpublished2013
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LibraryofCongressCataloging-in-PublicationData
CMOSvoltagereferences:ananalyticalandpracticalperspective/Chi-WahKok,Wing-ShanTam.–Firstedition.
pagescm
Includesbibliographicalreferencesandindex.
ISBN978-1-118-27568-9(hardback)
1.Voltagereferences. 2.Electriccircuitanalysis. 3.Electriccircuits–Designandconstruction. I.Kok,
Chi-Wah. II.Tam,Wing-Shan. III.Title:Voltagereference.
TK454.C6282013
621.3815(cid:3)28–dc23
2012030274
ISBN:9781118275689
Setin10/12ptTimesbyAptaraInc.,NewDelhi,India
CONTENTS
AbouttheAuthors ix
Preface xi
Acknowledgements xiii
Nomenclature xv
1 WarmUp 1
1.1 BipolarJunctionTransistors 2
1.1.1 DifferentialV 5
BE
1.2 Metal-OxideSemiconductorField-EffectTransistor 7
1.2.1 CutoffRegion 11
1.2.2 SubthresholdConduction 11
1.2.3 TriodeRegion 14
1.2.4 SaturationRegion 16
1.2.5 ThermalProperties 19
1.2.6 ChannelLengthModulationEffect 23
1.3 Diode 23
1.4 Resistor 25
1.4.1 DummyElement 27
1.4.2 GuardRing 27
1.4.3 SheetResistance 27
1.5 DeviceMatching 28
1.5.1 ApplicationofStatisticstoCircuitDesign 28
1.5.2 SystematicVariation 30
1.6 SimulationModelsforCircuitDesign 31
1.6.1 ProcessVariationandTypicalDesign 32
1.6.2 ProcessCorners 34
1.7 Noise 36
1.7.1 TypesofNoises 36
1.7.2 SumsandMultiplicationsofNoises 38
1.8 FabricationTechnology 39
1.9 BookOrganization 40
1.10 Exercises 42
References 46
vi Contents
2 VoltageReference 49
2.1 PerformanceMeasures 49
2.1.1 LineRegulation 51
2.1.2 TemperatureCoefficient 54
2.1.3 PowerSupplyRejectionRatio 56
2.1.4 QuiescentCurrent 59
2.1.5 OutputNoise 60
2.2 OtherDesignConsiderations 62
2.3 Summary 63
2.4 Exercises 65
References 70
3 BandgapVoltageReference 71
3.1 WidlarBandgapVoltageReferenceCircuit 71
3.2 DrainVoltageEqualizationCurrentMirror 74
3.2.1 OpampBasedβ-MultiplierBandgapVoltageReferenceCircuit 76
3.2.2 BandgapVoltageReferenceCircuit 77
3.3 MajorCircuitElements 81
3.3.1 OperationalAmplifier 81
3.3.2 CurrentMirror 86
3.3.3 StartupCircuit 88
3.3.4 ResistorNetwork 93
3.3.5 BipolarTransistor 94
3.4 CompleteLayout 95
3.5 Summary 95
3.6 Exercises 96
References 101
4 ErrorSourcesinBandgapVoltageReferenceCircuit 103
4.1 Non-IdealOpamp 103
4.1.1 InputOffsetVoltage 104
4.1.2 LimitedGainandPowerSupplyRejectionRatio 112
4.1.3 Noise 113
4.2 CurrentMirrorMismatch 114
4.2.1 ChannelLengthModulationEffectCompensation 116
4.2.2 CascodeCurrentMirror 117
4.3 BipolarTransistor 122
4.3.1 SizeVariation 122
4.3.2 SeriesBaseResistance 122
4.3.3 β Variation 125
4.4 ResistorVariation 126
4.5 PowerSupplyVariation 127
4.5.1 Pre-Regulation 132
4.6 OutputLoading 135
4.7 OutputNoise 138
4.8 VoltageReferenceCircuitTrimming 140
Contents vii
4.8.1 LinkedFuseResistorTrimming 141
4.8.2 ResistorTrimmingCircuitAnalysis 142
4.8.3 ModulatedTrimming 146
4.8.4 VoltageDomainTrimming 148
4.8.5 CurrentDomainTrimming 149
4.9 Summary 149
4.10 Exercises 151
References 161
ADVANCEDVOLTAGEREFERENCECIRCUITS
5 TemperatureCompensationTechniques 165
5.1 V −(cid:3)V Compensation 166
BE BE
5.1.1 BrokawBandgapVoltageReference 168
5.1.2 β-MultiplierV −(cid:3)V Compensation 170
BE BE
5.2 WidlarPTATCurrentSourceandV Compensation 175
BE
5.3 V BasedTemperatureCompensation 177
GS
5.3.1 V CurrentSource 178
GS
5.4 Summary 182
5.5 Exercises 183
References 189
6 Sub-1VVoltageReferenceCircuit 191
6.1 Sub-1VOutputStage 193
6.2 VoltageHeadroominOpampbasedβ-multiplierVoltageReferenceCircuit 195
6.2.1 OpampwithNMOSInputStage 197
6.2.2 LocalVoltageBoosting 198
6.2.3 LowV Transistor 198
th
6.2.4 Bulk-DrivenTransistors 199
6.3 Sub-1VBandgapVoltageReferencebyResistiveDivision 199
6.3.1 ResistiveDividedV 202
BE
6.3.2 IndependentBiasedResistiveDividedV 206
BE
6.4 PeakingCurrentSourceandV Compensation 209
BE
6.5 Weighted(cid:3)V Compensation 211
GS
6.6 Summary 214
6.7 Exercises 215
References 222
7 HighOrderCurvatureCorrection 223
7.1 CompensationOrder 224
7.2 SecondOrderTemperatureCompensation 228
7.2.1 SecondOrderCurrentSource 229
7.2.2 CurrentSubtraction 232
7.2.3 CurrentAddition 236
7.3 BJTCurrentSubtraction 238
7.4 PiecewiseLinearCompensation 240
viii Contents
7.5 SumandDifferenceofSourceswithSimilarTemperatureDependence 243
7.5.1 DifferenceofVoltageswithSimilarTemperatureDependence 244
7.5.2 SumofVoltageswithInvertedTemperatureDependence 245
7.5.3 Multi-thresholdVoltagesCurvatureCompensatedVoltage
Reference 247
7.6 Summary 252
7.7 Exercises 253
References 257
8 CMOSVoltageReferencewithoutResistors 259
8.1 GenerationofWeightedPTATSourceByInverseFunctions 260
8.1.1 WeightedDifferentialCircuit 260
8.1.2 NegativeImpedanceConverter 262
8.2 ResistorlessVoltageandCurrentSources 265
8.2.1 ResistorlessVoltageSource 265
8.2.2 ResistorlessCurrentSource 266
8.3 FirstOrderCompensatedResistorlessBandgapVoltageReferenceCircuit 268
8.3.1 VoltageSummationBasedResistorlessReferenceCircuit 269
8.3.2 CurrentSummationBasedResistorlessReferenceCircuit 270
8.4 ResistorlessSub-BandgapReferenceCircuit 270
8.4.1 TheVoltageSummationApproach 271
8.4.2 CTATVoltageReduction 273
8.5 Summary 279
8.6 Exercises 280
References 281
A SPICEModelFile 283
B SPICENetlistofVoltageReferenceCircuit 287
Index 289
ABOUT THE AUTHORS
Chi-WahKokwasborninHongKong.HewasgrantedaPhDdegreefromtheUniversityof
WisconsinMadison.Since1992,hehasbeenworkingwithvarioussemiconductorcompanies,
researchinstitutions,anduniversities,whichincludeAT&TLabsResearch,Holmdel,SONY
U.S.ResearchLabs,StanfordUniversity,HongKongUniversityofScienceandTechnology,
HongKongPolytechnicUniversity,CityUniversityofHongKong,LatticeSemiconductor,etc.
In2006,hefoundedCanaanMicroelectronicsCorpLtd.,afablessICcompanywithproducts
inmixedsignalICforconsumerelectronics.Dr.Kokembracesnewtechnologiestomeetthe
fastchangingmarketrequirements.Hehasextensivelyappliedsignalprocessingtechniques
toimprovethecircuittopologies,designs,andfabricationtechnologieswithinCanaan.This
includestheapplicationofsemidefiniteprogrammingtocircuitdesignoptimization,abstract
algebra in switched capacitor circuit topologies improvement, and nonlinear optimization
methodstooptimizehighvoltageMOSFETlayoutandfabrication.
Wing-Shan Tam was born in Hong Kong. She received her BEng degree in electronic
engineering from The Chinese University of Hong Kong, MSc degree in electronic and
information engineering from The Hong Kong Polytechnic University, and PhD degree in
electronic engineering from the City University of Hong Kong in 2004, 2007, and 2011,
respectively.Currently,sheistheEngineeringManagerofCanaanMicroelectronicsCorpLtd.
Herresearchinterestsincludemixed-signalintegratedcircuitdesignfordataconversionand
power-management.
PREFACE
This book has a genesis: It started as internal training material for engineers working in
Canaan Microelectronics Corp. Ltd. It is also a monograph because it presents the outcome
ofourresearchandteachingactivitiesinthefieldoftemperatureindependentcircuitdesign
atboththeCanaanMicroelectronicsCorp.Ltd.andtheCityUniversityofHongKong.Many
unpublishedworksareincludedinthisbook.Numerousdesignexamplesarealsopresented
togetherwithdetaileddiscussionsondesignprinciples,performanceanalysis,andthepotential
problemsofeachcircuittopology.Thisbookisintendedtobecoursematerialforseniorand
graduate level courses, training material for engineers, and also a reference text for readers
whoareworkinginthefieldoftemperatureindependentcircuitdesign.
The book is divided into eight chapters. The first chapter offers an introduction of device
physics focusing on the temperature properties of individual devices, which introduces just
enough material for voltage reference circuit design and analysis. Details of general device
physicsmaybegatheredfromexistingliterature,suchasthetextbooksbyChenmingC.Hu,
(ModernSemiconductorDevicesforIntegratedCircuits,PrenticeHall,2010),andS.M.Sze,
(PhysicsofSemiconductorDevices,Wiley,1969)thatofferdetaileddiscussionsonthedevice
physicsforbipolartransistors,MOStransistors,andotherpassivecomponentsmanufacturedin
theCMOSprocess.Besidesthephysics,towardstheendofChapter1,wealsodiscusspractical
issuesinCMOScircuitdesign.Thedevicematchingproblemisintroduced.Computersimu-
lationforcircuitdesignwithprocessvariationsisdiscussed.Finally,thedevicenoisemodels
thatdescribethenoisesassociatedwithCMOSdevicesarepresented.Chapter2presentsthe
performancecharacterizationofvoltagereferencecircuits.Thepresentedcharacterizationwill
be used throughout the book in the analytical discussions and performance comparisons of
individualvoltagereferencecircuits.Ageneralvoltagereferencecircuitframeworkofopamp
basedβ-multiplierbandgapvoltagereferenceispresentedinChapter3.Thepresentedvoltage
referencecircuitissiliconproven,andhasbeenappliedtoapowermanagementICofCanaan
MicroelectronicsCorp.Ltd.:themicrographofthedieisshownonthefrontpageofthisbook.
Everybuildingblockwithinthevoltagereferencecircuitisdiscussedanalyticallytogetherwith
layout details. Various error sources of the circuit are identified, and analyzed in Chapter 4.
Methodstoremedyeachproblemtogetherwiththeirprosandconsarediscussedindetailin
Chapter4.ThebasicPTAT-CTATtemperaturecompensationtechniquediscussedinChapter4
will be extended to voltage reference circuits using various temperature dependent devices
andtopologiesinChapter5.Analyticalderivationtodeterminethecomponentvaluesofeach
devicewithinthevoltagereferencecircuit,togetherwiththeimportantdesignconsiderations
of each circuit and topology will be discussed. Chapter 6 discusses the design of voltage
xii Preface
reference circuits with sub-1V supply, and voltage reference circuits with sub-1V reference
voltage.Noticethatthedesignofthevoltagereferencecircuitwithasub-1Vreferencevoltage
isdifferentfromthatofthevoltagereferencecircuitwithasub-1Vsupplyvoltage.Avoltage
referencecircuitwithasub-1Vsupplyvoltageisalsoavoltagereferencecircuitwithasub-1V
referencevoltage.Thevoltagereferencecircuitwithsub-1Vreferencevoltagebeingableto
operatewithasub-1VsupplyvoltageisimportantinmodernCMOScircuitdesignwherethe
supply voltage keeps reducing for power reduction and silicon size shrinkage. A number of
sub-1Vvoltagereferencecircuitswillbediscussedinthischapter.
High order curvature compensated voltage reference circuits are presented in Chapter 7,
which are important to applications that require a reference voltage with low temperature
sensitivity. A number of high accuracy voltage reference circuit topologies, including high
ordercurvaturecompensation,invertedtemperaturecompensation,andpiecewisetemperature
compensation etc. are discussed. This book concludes in Chapter 8 with a discussion on
a type of special voltage reference circuit that does not require resistors. Such a voltage
reference circuit has the advantage of compact layout. The performance of a resistor free
voltagereferencecircuitcanbefurtheroptimizedwithapplicationsofpiecewisetemperature
compensation technique to lower the temperature sensitivity of the circuit. Post-fabrication
trimmingcircuitsarediscussedtoreducethereferencevoltagevariation.
A detailed summary of the state of the art development with respect to the topic of each
chapter is presented in the “Summary” section of each chapter. Homework problems are
presentedinthe“Exercise”sectioninindividualchapter.Thehomeworkincludesbothanalytic
problems,andSPICEbasedcomputersimulationexercises.Whiletheprocessparametersused
inthisbookandalsoindevelopingtheexercisesmaynotbethesameasthoseinyourinstitution,
itisourhopethattheexerciseswillprovideyouwithgeneralguidelines,analysis,designand
layoutexperienceforthedesignofthevoltagereferencecircuitswiththehelpofSPICE.The
experience will further address the performance evaluation of the voltage reference circuit
whichwillhelpyoutoachieveathoroughconsiderationofthevoltagereferencecircuitbefore
theactualdesign.
Thedevelopmentofvoltagereferencecircuitsisstillcontinuingandthereforeabook,such
as this one, cannot be definitive or complete. It is hoped, however, that this book will fill
an important gap; students embarking upon mixed-signal circuit design should be able to
learn sufficient basics before tackling journal papers, researchers and engineers in the field
oftemperatureindependent/dependent circuitdesignshouldbeabletouseitasreferenceto
assist their circuit design tasks, and current researchers in the field should be able to get a
broad perspective on what has been achieved. The subject area is introduced, some major
developments are recorded, and enough successes as well as challenges are noted here for
readerstolookintoothervoltageindependent/dependentcircuitdesignproblemsandgenerate
solutionsfortheirownproblems.
Chi-WahKokandWing-ShanTam
February2012