Current Sensing Techniques and Biasing Methods for Smart Power Drivers

154 Pages·2018·6.586 MB·English

by  Sri Navaneethakrishnan Easwaran (auth.)

Sri Navaneethakrishnan Easwaran
Current Sensing
Techniques and
Biasing Methods for
Smart Power Drivers
Current Sensing Techniques and Biasing Methods
for Smart Power Drivers
Sri Navaneethakrishnan Easwaran
Current Sensing Techniques
and Biasing Methods for
Smart Power Drivers
SriNavaneethakrishnanEaswaran
TexasInstruments(UnitedStates)
Dallas,TX,USA
ISBN978-3-319-71981-8 ISBN978-3-319-71982-5 (eBook)
https://doi.org/10.1007/978-3-319-71982-5
LibraryofCongressControlNumber:2017960427
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With tons of thanks to my supervisor
Prof. Dr. R. Weigel, Friedrich-Alexander-
Universität Erlangen-Nu€rnberg.
Abstract
The demand for electronic control is increasing in the automotive industry and is
quickly replacing hydraulics. Automobiles produced today have a longer life
expectancy, and one of the strongest contributors to this is how electronic equip-
ment and systems have replaced mechanical devices. Without proper electrical
protection, however, these electronic systems in automobiles can fail without
warning. This creates a risk for both the driver and passengers, including injury
and death. Powersemiconductor devices that are used in these electronic systems
handlehighcurrentsintheorderof2Aat40V.Duetothishighvoltageandhigh
current, several design measures have to be considered when designing how to
makethesecircuitsfaulttolerant.Theunintentionalorinadvertentactivationofthe
powerFETsshouldbeavoidedtopreventveryhighcurrents.Thisbookcontributes
tothedesignofsmartpowerdriversforairbagsquibdriverapplications.Itfocuses
on the current regulation circuits with fault-tolerant topologies and inadvertent
current control. Inadvertent current flows can damage safety ASICs or even alter
safety functionality. The designs have to be developed to withstand faults like
missing power supply in a Multiple Supply Domain ASIC that can lead to high
currentsduetofloatingnodes.Thesmartpowerdriversshouldbeguaranteedtonot
misfire the airbags when some supplies are missing. Other faults that can lead to
airbag misfire are short-to-battery and short-to-ground conditions, which happen
duringeitherthepoweredorunpoweredstateoftheASIC.
This book extends the technical state of the art and improves on it by the
followingprincipleresults:
1. Thecurrentsensingschemeisdesignedtoachievethedesiredcurrentlimitation
in the high-side configuration with a metal sense resistor. In addition to the
current regulation, the novel surge current control circuit to limit the current
through the powerFET is needed to limit the duration of the peak current. The
importanceofthisisexplainedandverified.Thedurationis5Afor4μs.
2. Acurrentsensingschememeanttoachievethedesiredcurrentlimitationinthe
low-sideconfigurationwithasenseFET-basedtopologyispresented.Thenovel
vii
viii Abstract
surge current control circuit is meant to ensure that the circuit is fault tolerant
whenashort-circuit-tobattery(SCB)conditionoccurs.Thedurationis5Afor
4μs.
3. The exploitation of current selector circuits to ensure well-defined bias condi-
tions for the powerFETs and circuits operating with multiple supply voltages
(MSVs)isdiscussed.
4. A diagnostic section is discussed with two specific targets. Diagnostic circuits
consist of a voltage reference circuit and an output buffer. The design of a
precisecurrentlimitedvoltagesource(CLVS)isdiscussed.Thecommonmode
inputoftheoutputbuffercanrangefrom0to40V,buttheoutputlevelofthis
bufferislimitedto5.5Vbyanimprovedclampingtechnique.
Afour-channelsquibdriverprototypehasbeenmanufacturedona350nm,40V
BiCMOS process. Extensive measurements have been performed for the current
sensing circuits on both high-side and low-side configurations. The high-side
currentsensingschemeregulatesto2Awith(cid:1)3%accuracy.Thelow-sideconfig-
uration regulates to 3 A with (cid:1)10% accuracy. The peak current limitation in the
unpoweredstateis1Afor400nsand3Afor1.5μsforthehigh-sideandlow-side
configurations,respectively.Thehigh-sideandlow-sidedrivershavestablecurrent
regulation for inductive loads up to 3 mH. High-side drivers provide an internal
freewheelingpathduringturnoffconditions.Thebiasingschemeintroducedwith
voltage and current selectors did not show any unintended activation or deactiva-
tion of the circuits under any power-up condition. Current limited voltage source
fordiagnosticsimplementedinbothhigh-sideandlow-sideconfigurationsregulate
to 8.4 V with (cid:1)0.5 V accuracy. Output buffers regulate to 5.4 V with (cid:1)200 mV
accuracyunderanypower-upphaseofoperation.
Acknowledgements
ThisbookistheresultofmyDoctorofPhilosophyassignmentatTexasInstruments
Inc.,Dallas,Texas,USA.TheprojectwascarriedoutfromJanuary2010toAugust
2016 at the Mixed Signal Automotive (MSA) group at Texas Instruments Inc. It
was used to complete my Doctor of Philosophy in Electrical Engineering in the
DepartmentElektrotechnikattheUniversitätErlangen-Nürnberg.
I would like to thank Mr. Joseph A. Devore, product line manager, Integrated
Automotive Products (IAP), for allowing me to lead the airbag squib driver
development project, which hasbeeninstrumentalforthisdissertation. He helped
me in my career at Texas Instruments Inc., and supported me while I wrote my
thesis. I would like to thank Mr. Sigfredo Gonzalez Diaz, engineering manager,
IAP,andmysupervisorMr.BenjaminAmeyfortheirencouragementandsupport
onthisproject.
I would like to convey my deepest gratitude to Prof. Dr.-Ing. habil. Robert
Weigel for taking me on as his external PhD candidate. He guided me towards
the completion of my thesis. His support was exceptional, and I appreciate the
individualized attention he gave to me, taking the time to clarify my queries and
correct mymistakes eventhoughwewerelocatedontwodifferentcontinents.As
mysupervisor,heconstantlypushedmetoachievemygoals.Hisobservationsand
comments helped me to establish the overall direction of the research and move
forwardwiththeinvestigation.IwouldliketothankProf.Dr.-Ing.MartinMärzfor
allhissupportaswell.Hegladlyacceptedtobeoneofmyreviewersandprovided
additional,helpfulfeedbacktoimprovemythesis.
IgreatlyappreciateDr.ShanmuganandChellamuthuatTexasInstrumentsInc.,
Dallas, Texas, USA, for all his guidance, too. His support was exceptional, espe-
cially in how he helped me systematically organize my thesis. I would like to
expressmygratitudetoDr.SamirCamdzicandDr.RalfBrederlow,TexasInstru-
mentsGmbH,Freising,Germany,aswellfortheirconstructivefeedback.Iamalso
gratefulandthankfultoDr.KrishnaswamyNagaraj(TIFellow)andDr.JingweiXu
(TIFellow)fortheirreviewsandvaluablefeedback.Ihavenowordstoexpressmy
gratitude for the support from Mr. Larry Bassuk and Mr. Bill Kempler, Legal
ix
x Acknowledgements
Department, Texas Instruments Inc., Dallas, Texas, USA, for helping me publish
mythesis.
I thank Prof. Dr. Chandra Sekhar, CEERI, Pilani, India, Prof. Dr. ir. M.J.M.
Pelgrom and Prof. Dr. ir. B. Nauta and his staff, ICD, University of Twente,
Enschede, The Netherlands, for being a source of inspiration. I would like to
thank several of my professors and airbag control unit experts who have been a
significantsourceofknowledgeandinspirationformyresearch.
I would like to thank my colleague Mr. Sunil Kashyap Venugopal, Texas
InstrumentsInc.,Dallas,Texas,USA,forprovidingmethedigitaldesignsupport.
Ithankmyparentsfortheirsupportandblessings,mywifeHemalathaanddaughter
Vaisshnavifortheirunconditionalsupportandencouragement,andmybrotherSai
forhissupport.
Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 AutomotiveElectronicSystem. . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 SquibDriverFunction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 SquibDriverTrueDeploymentandInadvertent
DeploymentConditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 CurrentSensingandRegulation. . . . . . . . . . . . . . . . . . . . . . . . 8
1.5 BiasingScheme. . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . 9
1.6 VoltageReferenceandVoltageClamping. . . . . . . . . . . . . . . . . 10
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2 State-of-the-ArtCurrentSensing,BiasingSchemesand
VoltageReferences.. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . 13
2.1 State-of-the-ArtCurrentSensingSchemesHS_FET. . . . . . . . . 13
2.2 State-of-the-ArtCurrentSensingSchemesLS_FET. . . . . . . . . . 15
2.3 State-of-the-ArtEnergyLimitation. . . . . . . . . . . . . . . . . . . . . . 16
2.4 State-of-the-ArtBiasingSchemeinMultipleSupply
VoltageDomains. . . . . . . . .. . . . . . . . . .. . . . . . . . .. . . . . . . 17
2.5 State-of-the-ArtBiasingSchemeforDiagnostics. . . . . . . . . . . . 19
2.6 ProblemswiththeState-of-the-ArtTechniques. . . . . . . . . . . . . 20
2.7 Specification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.8 ChaptersOrganization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3 CurrentSensingPrincipleswithBiasingScheme. . . . . . . . . . . . . . 25
3.1 CurrentSensingCircuitwithSenseResistor. . . . . . . . . . . . . . . 25
3.2 CurrentSensingCircuitwithSenseResistorand
CurrentLimitation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.3 CurrentSensingCircuitwithSenseFETandCurrent
Limitation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.4 BiasingSchemes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.5 TypicalProblemsObservedinMSVDesigns. . . . . . . . . . . . . . 32
xi