MMA7260Q三轴加速度传感器.docx
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MMA7260Q三轴加速度传感器.docx
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MMA7260Q三轴加速度传感器
MMA7260QRev0,04/2005
FreescaleSemiconductor
TechnicalData
©FreescaleSemiconductor,Inc.,2005.Allrightsreserved.
±1.5g-6gThreeAxisLow-gMicromachinedAccelerometer
TheMMA7260Qlowcostcapacitivemicromachinedaccelerometerfeaturessignalconditioning,a1-polelowpassfilter,temperaturecompensationandg-Selectwhichallowsfortheselectionamong4
sensitivities.Zero-goffsetfullscalespanandfiltercut-offarefactorysetandrequirenoexternaldevices.IncludesaSleepModethatmakesitidealforhandheldbatterypoweredelectronics.Features•SelectableSensitivity(1.5g/2g/4g/6g•LowCurrentConsumption:
500µA•SleepMode:
3µA
•LowVoltageOperation:
2.2V–3.6V•6mmx6mmx1.45mmQFN
•HighSensitivity(800mV/g@1.5g•FastTurnOnTime•HighSensitivity(1.5g
•IntegralSignalConditioningwithLowPassFilter•RobustDesign,HighShocksSurvivability•Pb-FreeTerminations
•EnvironmentallyPreferredPackage•
LowCost
TypicalApplications•HDDMP3Player:
FreefallDetection•LaptopPC:
FreefallDetection,Anti-Theft
•CellPhone:
ImageStability,TextScroll,MotionDialing,E-Compass•Pedometer:
MotionSensing•PDA:
TextScroll
•NavigationandDeadReckoning:
E-CompassTiltCompensation•Gaming:
TiltandMotionSensing,EventRecorder•
Robotics:
MotionSensing
ORDERINGINFORMATION
DeviceNameTempertureRangeCaseNo.PackageMMA7260Q–20to+85°C1622-01QFN-16,TubeMMA7260QR2
–20to+85°C
1622-01
QFN-16,Tape&Reel
MMA7260Q
MMA7260Q:
XYZAXISACCELEROMETER±
1.5g/2g/4g/6g
16
15
14
13
567812
34
1211109g-Select1g-Select2
VDDVSSSleepModeN/CN/CN/C
N/C
N/C
N/C
N/C
N/C
XOUT
YOUTZOUTFigure1.PinConnections
TopView
MMA7260QSensors
2-2
FreescaleSemiconductor
Figure2.SimplifiedAccelerometerFunctionalBlockDiagram
ELECTROSTATICDISCHARGE(ESD
WARNING:
Thisdeviceissensitivetoelectrostatic
discharge.AlthoughtheFreescaleaccelerometercontainsinternal2000VESDprotectioncircuitry,extraprecautionmustbetakenbytheusertoprotectthechipfromESD.Achargeofover2000voltscanaccumulateonthehumanbodyorassociatedtestequipment.Achargeofthismagnitudecan
altertheperformanceorcausefailureofthechip.Whenhandlingtheaccelerometer,properESDprecautionsshouldbefollowedtoavoidexposingthedevicetodischargeswhichmaybedetrimentaltoitsperformance.
Table1.MaximumRatings
(Maximumratingsarethelimitstowhichthedevicecanbeexposedwithoutcausingpermanentdamage.
Rating
SymbolValueUnitMaximumAcceleration(allaxisgmax±2000gSupplyVoltageVDD–0.3to+3.6
VDropTest(1
1.Droppedontoconcretesurfacefromanyaxis.
Ddrop1.8mStorageTemperatureRange
Tstg
–40to+125
°C
VSS
ZOUT
YOUT
XOUT
g-Select1g-Select2
SleepMode
VDD
G-CellSensor
Oscillator
ClockGenerator
X-TempComp
Y-TempComp
Z-TempComp
CtoVConverter
Gain+Filter
ControlLogicEEPROMTrimCircuits
MMA7260Q
Sensors
FreescaleSemiconductor
2-3
Table2.OperatingCharacteristics
ADD(1
Characteristic
SymbolMinTypMaxUnit
OperatingRange(2SupplyVoltage(3SupplyCurrent
SupplyCurrentatSleepMode
(4
OperatingTemperatureRange
AccelerationRange,X-Axis,Y-Axis,Z-Axisg-Select1&2:
00g-Select1&2:
10g-Select1&2:
01g-Select1&2:
11VDDIDDIDDTAgFSgFSgFSgFS2.2——–20————
3.35003—±1.5±2.0±4.0±6.0
3.680010+85————
VµAµA°Cgggg
OutputSignal
Zerog(TA=25°C,VDD=3.3V(5Zerog
Sensitivity(TA=25°C,VDD=3.3V1.5g2g4g6gSensitivity
BandwidthResponseXYZVOFFVOFF,TAS1.5gS2gS4gS6gS,TAf-3dBf-3dB1.485—740555277.5185———
1.65±2800600300200±3350150
1.815—860645322.5215———
Vmg/°CmV/gmV/gmV/gmV/g%/°CHzHz
Noise
RMS(0.1Hz–1kHz(4
PowerSpectralDensityRMS(0.1Hz–1kHz(4nRMSnPSD——
4.7350
——
mVrmsµg/ControlTiming
Power-UpResponseTime(6EnableResponseTime(7
SensingElementResonantFrequencyXYZ
InternalSamplingFrequencytRESPONSEtENABLEfGCELLfGCELLfCLK—————
1.00.56.03.411
2.02.0———
msmskHzkHzkHz
OutputStagePerformance
Full-ScaleOutputRange(IOUT=30µAVFSOVSS+0.25—VDD–0.25VNonlinearity,XOUT,YOUT,ZOUTNLOUT–1.0—+1.0%FSOCross-AxisSensitivity(8
VXY,XZ,YZ
—
—
5.0
%
1.Foraloadedoutput,themeasurementsareobservedafteranRCfilterconsistingofa1.0kΩresistoranda0.1µFcapacitortoground.2.Theselimitsdefinetherangeofoperationforwhichthepartwillmeetspecification.
3.Withinthesupplyrangeof2.2and3.6V,thedeviceoperatesasafullycalibratedlinearaccelerometer.Beyondthesesupplylimitsthedevicemayoperateasalineardevicebutisnotguaranteedtobeincalibration.4.Thisvalueismeasuredwithg-Selectin1.5gmode.
5.Thedevicecanmeasureboth+and–acceleration.Withnoinputaccelerationtheoutputisatmidsupply.ForpositiveaccelerationtheoutputwillincreaseaboveVDD/2.Fornegativeacceleration,theoutputwilldecreasebelowVDD/2.6.Theresponsetimebetween10%offullscaleVddinputvoltageand90%ofthefinaloperatingoutputvoltage.7.Theresponsetimebetween10%offullscaleSleepModeinputvoltageand90%ofthefinaloperatingoutputvoltage.8.Ameasureofthedevice’sabilitytorejectanaccelerationapplied90°fromthetrueaxisofsensitivity.
MMA7260QSensors
2-4
FreescaleSemiconductor
PRINCIPLEOFOPERATION
TheFreescaleaccelerometerisasurface-micromachinedintegrated-circuitaccelerometer.
Thedeviceconsistsoftwosurfacemicromachinedcapacitivesensingcells(g-cellandasignalconditioningASICcontainedinasingleintegratedcircuitpackage.Thesensingelementsaresealedhermeticallyatthewaferlevelusingabulkmicromachinedcapwafer.
Theg-cellisamechanicalstructureformedfrom
semiconductormaterials(polysiliconusingsemiconductorprocesses(maskingandetching.Itcanbemodeledasasetofbeamsattachedtoamovablecentralmassthatmovebetweenfixedbeams.Themovablebeamscanbedeflectedfromtheirrestpositionbysubjectingthesystemtoanacceleration(Figure3.
Asthebeamsattachedtothecentralmassmove,thedistancefromthemtothefixedbeamsononesidewillincreasebythesameamountthatthedistancetothefixedbeamsontheothersidedecreases.Thechangeindistanceisameasureofacceleration.
Theg-cellbeamsformtwoback-to-backcapacitors
(Figure3.Asthecenterbeammoveswithacceleration,thedistancebetweenthebeamschangesandeachcapacitor'svaluewillchange,(C=Aε/D.WhereAistheareaofthebeam,εisthedielectricconstant,andDisthedistancebetweenthebeams.
TheASICusesswitchedcapacitortechniquestomeasuretheg-cellcapacitorsandextracttheaccelerationdatafromthedifferencebetweenthetwocapacitors.TheASICalsosignalconditionsandfilters(switchedcapacitorthesignal,providingahighleveloutputvoltagethatisratiometricandproportionaltoacceleration.
Figure3.SimplifiedTransducerPhysicalModel
SPECIALFEATURES
g-Select
Theg-Selectfeatureallowsfortheselectionamong4sensitivitiespresentinthedevice.Dependingonthelogicinputplacedonpins1and2,thedeviceinternalgainwillbechangedallowingittofunctionwitha1.5g,2g,4g,or6gsensitivity(Table3.Thisfeatureisidealwhenaproducthasapplicationsrequiringdifferentsensitivitiesforoptimumperformance.Thesensitivitycanbechangedatanytimeduringtheoperationoftheproduct.Theg-Select1andg-Select2pinscanbeleftunconnectedforapplications
requiringonlya1.5gsensitivityasthedevicehasaninternalpulldowntokeepitatthatsensitivity(800mV/g.SleepMode
The3axisaccelerometerprovidesaSleepModethatisidealforbatteryoperatedproducts.WhenSleepModeisactive,thedeviceoutputsareturnedoff,providingsignificantreductionofoperatingcurrent.Alowinputsignalonpin12(SleepModewillplacethedeviceinthismodeandreducethecurrentto3uAtyp.Forlowerpowerconsumption,itisrecommendedtosetg-Select1andg-Select2to1.5gmode.Byplacingahighinputsignalonpin12,thedevicewillresumetonormalmodeofoperation.
Filtering
The3axisaccelerometercontainsonboardsingle-poleswitchedcapacitorfilters.Becausethefilterisrealizedusingswitchedcapacitortechniques,thereisnorequirementforexternalpassivecomponents(resistorsandcapacitorstosetthecut-offfrequency.
Ratiometricity
Ratiometricitysimplymeanstheoutputoffsetvoltageandsensitivitywillscalelinearlywithappliedsupplyvoltage.Thatis,assupplyvoltageisincreased,thesensitivityandoffsetincreaselinearly;assupplyvoltagedecreases,offsetandsensitivitydecreaselinearly.Thisisakeyfeaturewhen
interfacingtoamicrocontrolleroranA/Dconverterbecauseitprovidessystemlevelcancellationofsupplyinducederrorsintheanalogtodigitalconversionprocess.
Acceleration
Table3.g-SelectpinDescriptions
g-Select2
g-Select1
g-RangeSensitivity001.5g800mV/g012g600mV/g104g300mV/g1
1
6g
200mV/g
MMA7260Q
Sensors
FreescaleSemiconductor
2-5
BASICCONNECTIONS
PinDescriptions
Figure4.PinoutDescription
Figure5.AccelerometerwithRecommended
ConnectionDiagram
PCBLayout
Figure6RecommendedPCBLayoutforInterfacing
AccelerometertoMicrocontrollerNOTES:
1.Use0.1µFcapacitoronVDDtodecouplethepowersource.
2.Physicalcouplingdistanceoftheaccelerometertothemicrocontrollershouldbeminimal.3.Flagunderneathpackageisconnectedtoground.4.Placeagroundplanebeneaththeaccelerometertoreducenoise,thegroundplaneshouldbeattachedtoalloftheopenendedterminalsshowninFigure6.5.UseanRCfilterwith1.0kΩand0.1µFonthe
outputsoftheaccel
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