Sensors for Low Level Signal Acquisition (Design Conference 2013)
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Sensors for Low Level Signal Acquisition (Design Conference 2013)

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Sensors are the eyes, ears, and hands of electronic systems and allow them to capture the state of the environment. The capture and processing of sensor inputs is a delicate process that requires ...

Sensors are the eyes, ears, and hands of electronic systems and allow them to capture the state of the environment. The capture and processing of sensor inputs is a delicate process that requires understanding of the signal details.Integration of sensor functions onto silicon has brought about improved performance, better signal handling, and lower total system cost. MEMS (microelectromechanical systems) sensors have opened up entire new areas and applications. In this session, the fundamental MEMS sensor concept of moving fingers that form a variable capacitor is covered, along with how it is turned into a usable motion signal. Adaptations for multiaccess sensing, rotational sensing, and even sound sensing, along with concepts of how these devices are tested and calibrated are covered.

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Sensors for Low Level Signal Acquisition (Design Conference 2013) Sensors for Low Level Signal Acquisition (Design Conference 2013) Presentation Transcript

  • Sensors for Low Level SignalAcquisitionAdvanced Techniques of Higher Performance Signal Processing
  • Legal Disclaimer Notice of proprietary information, Disclaimers and Exclusions Of WarrantiesThe ADI Presentation is the property of ADI. All copyright, trademark, and other intellectual property andproprietary rights in the ADI Presentation and in the software, text, graphics, design elements, audio and all othermaterials originated or used by ADI herein (the "ADI Information") are reserved to ADI and its licensors. The ADIInformation may not be reproduced, published, adapted, modified, displayed, distributed or sold in any manner, inany form or media, without the prior written permission of ADI.THE ADI INFORMATION AND THE ADI PRESENTATION ARE PROVIDED "AS IS". WHILE ADI INTENDS THE ADIINFORMATION AND THE ADI PRESENTATION TO BE ACCURATE, NO WARRANTIES OF ANY KIND ARE MADEWITH RESPECT TO THE ADI PRESENTATION AND THE ADI INFORMATION, INCLUDING WITHOUT LIMITATIONANY WARRANTIES OF ACCURACY OR COMPLETENESS. TYPOGRAPHICAL ERRORS AND OTHERINACCURACIES OR MISTAKES ARE POSSIBLE. ADI DOES NOT WARRANT THAT THE ADI INFORMATION ANDTHE ADI PRESENTATION WILL MEET YOUR REQUIREMENTS, WILL BE ACCURATE, OR WILL BEUNINTERRUPTED OR ERROR FREE. ADI EXPRESSLY EXCLUDES AND DISCLAIMS ALL EXPRESS AND IMPLIEDWARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT OFANY THIRD PARTY INTELLECTUAL PROPERTY RIGHTS. ADI SHALL NOT BE RESPONSIBLE FOR ANY DAMAGEOR LOSS OF ANY KIND ARISING OUT OF OR RELATED TO YOUR USE OF THE ADI INFORMATION AND THE ADIPRESENTATION, INCLUDING WITHOUT LIMITATION DATA LOSS OR CORRUPTION, COMPUTER VIRUSES,ERRORS, OMISSIONS, INTERRUPTIONS, DEFECTS OR OTHER FAILURES, REGARDLESS OF WHETHER SUCHLIABILITY IS BASED IN TORT, CONTRACT OR OTHERWISE. USE OF ANY THIRD-PARTY SOFTWAREREFERENCED WILL BE GOVERNED BY THE APPLICABLE LICENSE AGREEMENT, IF ANY, WITH SUCH THIRDPARTY.©2013 Analog Devices, Inc. All rights reserved.2
  • Today’s AgendaSensors are the sourceSensor signals are typically low level and difficultSignal conditioning is key to high performanceSilicon sensors are integrated with signal conditioningApplications keep demanding higher accuracyMotion sensors with moving silicon elements are driving systems inall market areas3
  • The GoalCapture what is going on in the real worldConvert into a useful electronic formatAnalyze, manipulate, store, and sendReturn to the real world4
  • The Real World Is NOT Digital5
  • Analog to Electronic Signal Processing6SENSOR(INPUT)DIGITALPROCESSORAMP CONVERTERACTUATOR(OUTPUT)AMP CONVERTER
  • The Sensor7SENSOR(INPUT)DIGITALPROCESSORAMP CONVERTERACTUATOR(OUTPUT)AMP CONVERTERAnalog, butNOT electronicAnalogAND electronic
  • Popular SensorsSensor Type OutputThermocouple VoltagePhotodiode CurrentStrain gauge ResistanceMicrophone CapacitanceTouch button Charge outputAntenna RF signalsAcceleration Capacitance8
  • Sensor Signal Conditioning9SENSOR AMPAnalog, electronic,but “dirty”Analog, electronic,and “clean” Amplify the signal to a noise-resistant level Lower the source impedance Linearize (sometimes but not always) Filter Protect
  • Designing Sensors in SiliconSensor signals are typically low level and subject tonoise coupling on connections to amplifiersBring signal conditioning as close to sensor as possible Multichip hybrids Silicon sensor on same chip as amplifier/data converterEnvironmental issues Extreme temperature or vibration Sensor needs to be small for sensitivityFinding silicon property that responds to physical variable Capacitance, stress, temperature change10
  • Silicon SensorsSensor Type OutputTemperature Voltage/currentPhotodiode CurrentStrain gauge ResistanceMicrophone CapacitanceRotation CapacitanceAntenna RF signalsAcceleration Capacitance11
  • Types of Temperature Sensors12THERMOCOUPLE RTD THERMISTOR SEMICONDUCTORWidest Range:–184ºC to +2300ºCRange:–200ºC to +850ºCRange:0ºC to +100ºCRange:–55ºC to +150ºCHigh Accuracy andRepeatabilityFair Linearity Poor Linearity Linearity: 1ºCAccuracy: 1ºCNeeds Cold JunctionCompensationRequiresExcitationRequiresExcitationRequires ExcitationLow-Voltage Output Low Cost High Sensitivity 10mV/K, 20mV/K,or 1µA/K TypicalOutput
  • Basic Relationships for SemiconductorTemperature Sensors13IC ICVBE VN∆VBE VBE VNkTqN= − = ln( )VBEkTqICIS=ln =SCNINIqkTV×lnINDEPENDENT OF IC, ISONE TRANSISTORN TRANSISTORS
  • Classic Band Gap Temperature Sensor14"BROKAW CELL"R R+I2 ≅ I1Q2NAQ1AR2R1VN VBE(Q1)VBANDGAP = 1.205V+VINVPTAT = 2R1R2kTqln(N)∆VBE VBE VNkTqN= − = ln( )
  • Analog Temperature Sensors15ProductAccuracy(Max)Max AccuracyRangeOperatingTempRangeSupplyRangeMaxCurrent Interface PackageAD590 ±0.5°C±1.0°C25°C−25°C to +105°C−55°C to+150°C4 V to 30 V 298 µA Current out TO-52, 2-lead FP,SOIC, DieAD592 ±0.5°C±1.0°C25°C−55°C to +150°C−25°C to+105°C4 V to 30 V 298 µA Current out TO-92TMP35 ±2.0°C 0°C to 85°C−25°C to +100°C−55°C to+150°C2.7 V to 5.5 V 50 µA Voltage out TO-92,SOT23,SOICTMP36 ±3.0°C −40°C to +125°C −55°C to+150°C2.7 V to 5.5 V 50 µA Voltage out TO-92,SOT23,SOICAD221100 ±2.0°C −50°C to +150°C −55°C to+150°C4 V to 6.5 V 650 µA Voltage out TO-92,SOIC, DieAD22103 ±2.5°C 0°C to +100°C 0°C to+100°C2.7 V to 3.6 V 600 µA Voltage out TO-92,SOIC
  • Digital Temperature Sensors ComprehensivePortfolio of Accuracy Options16Product Accuracy (Max)Max AccuracyRangeInterface PackageADT7420/ADT7320±0.2°C±0.25°C−10°C to +85°C−20°C to +105°CI2C/SPI LFCSPADT7410/ADT7310 ±0.5°C −40°C to +105°C I2C/SPI SOICADT75±1°C (B grade)±2°C (A grade)0°C to 85°C−25°C to +100°CI2C MSOP, SOICADT7301±1°C 0°C to 70°CSPI SOT23, MSOPTMP05/TMP06±1°C 0°C to 70°CPWM SC70, SOT23AD7414/ADT7415±1.5°C −40°C to +70°CI2C SOT23, MSOPADT7302 ±2°C 0°C to 70°C SPI SOT23, MSOPTMP03/TMP04±4°C−20°C to +100°C PWM TO-92, SOIC, TSSOP
  • High Accuracy Temperature SensingApplicationsScientific, medical and aerospace Instrumentation Medical equipment Laser beam positionersTest and measurement Calorimeters Automatic test equipment Mass spectrometry Thermo cyclers/DNA analyzers Infrared imaging Data acquisition/analyzers Flow metersProcess control Instruments/controllersCritical asset monitoring Food and pharmaceuticalEnvironmental monitoring1717
  • Digital IC RTD ThermistorEase of UseSensor selection andsourcingReliable supply andspecificationsNeed to determine reliablesuppliers (specifications std.)Need to determine reliablesuppliers and specificationsExtra signal processingAdditional sourcing,selection, design,evaluation, testing,manufacturingNoPrecision ADC (≥16 bits)Current sourceAmp (optional)Precision resistorFilter capsADC (resolution is app specific)Current sourceAmp (optional)Precision resistorFilter capsLinearization No Yes YesCalibration No Yes YesResistance concerns No Yes YesSelf heating concerns No Yes YesReliability Contact resistance No Susceptible SusceptibleBatch variation No Susceptible SusceptibleTransmission noise No Susceptible SusceptiblePerformance Accuracy range Industrial Range Wide range Commercial rangeStability High High LowRepeatability High High LowHigh Performance Temperature MeasurementSensor Comparisond18
  • High Accuracy Temperature MeasurementSensor ComparisonSensor Type NTC ThermistorPT100 RTD(Thin Film)Digital ICADT7X20*Accuracy±0.1°C from 0 to 70°C±0.3°C from 0 to 100°CExcludes:Data conversionSignal conditioningSelf heating, noise, drift etc.±0.27°C from 0 to 100°(Class 1/3 B)Excludes:Data conversionSignal conditioningSelf heatingLead wire resistanceNoise, etc.±0.2°C from −10 to +85°C±0.25°C from −20 to +105°CLinearity Poor Medium to high HighThermal response Medium to fast Medium to fast Medium to fastLong term stability/reliability Low Medium to high HighSystem costHigh for low tolerance(±0.1/0.2°C)High LowCalibration required Yes Yes NoExtra components required Yes Yes No19*For thermistors and RTDs actual tolerances will degrade in assembled system.
  • ThermocoupleVery low level (µV/ºC)NonlinearDifficult to handleWires need insulationSusceptible to noiseFragile20
  • Common Thermocouples21Junction MaterialsTypical UsefulRange (°C)NominalSensitivity(µV/°C)ANSIDesignationPlatinum (6%)/Rhodium-Platinum (30%)/Rhodium38 to 1800 7.7 BTungsten (5%)/Rhenium-Tungsten (26%)/Rhenium0 to 2300 16 CChromel-Constantan 0 to 982 76 EIron-Constantan 0 to 760 55 JChromel-Alumel −184 to +1260 39 KPlatinum (13%)/Rhodium-Platinum0 to 1593 11.7 RPlatinum (10%)/Rhodium-Platinum0 to 1538 10.4 SCopper-Constantan −184 to +400 45 T
  • Thermocouple Output Voltagesfor Type J, K, and S Thermocouples22-250 0 250 500 750 1000 1250 1500 1750-100102030405060THERMOCOUPLEOUTPUTVOLTAGE(mV)TEMPERATURE (°C)TYPE JTYPE KTYPE S-250 0 250 500 750 1000 1250 1500 1750-100102030405060THERMOCOUPLEOUTPUTVOLTAGE(mV)TEMPERATURE (°C)TYPE JTYPE KTYPE S
  • Thermocouple Seebeck Coefficient vs.Temperature23-250 0 250 500 750 1000 1250 1500 1750010203040506070SEEBECKCOEFFICIENT-µV/°CTEMPERATURE (°C)TYPE JTYPE KTYPE S-250 0 250 500 750 1000 1250 1500 1750010203040506070SEEBECKCOEFFICIENT-µV/°CTEMPERATURE (°C)TYPE JTYPE KTYPE S
  • Thermocouple Basics24T1METAL AMETAL BTHERMOELECTRICEMFRMETAL A METAL AR = TOTAL CIRCUIT RESISTANCEI = (V1 – V2) / RV1 T1 V2T2V1 – V2METAL BMETAL A METAL AV1V1T1T1T2T2V2V2VMETAL AMETAL ACOPPER COPPERMETAL BMETAL BT3 T4V = V1 – V2, IF T3 = T4A. THERMOELECTRIC VOLTAGEB. THERMOCOUPLEC. THERMOCOUPLE MEASUREMENTD. THERMOCOUPLE MEASUREMENTIV1 T1METAL AMETAL BEMFRMETAL A METAL AR = TOTAL CIRCUIT RESISTANCEI = (V1 – V2) / RV1 T1 V2T2V1 – V2METAL BMETAL A METAL AV1V1T1T1T2T2V2V2VMETAL ACOPPER COPPERMETAL BMETAL BT3 T4V = V1 – V2, IF T3 = T4A. THERMOELECTRIC VOLTAGEB. THERMOCOUPLEC. THERMOCOUPLE MEASUREMENTD. THERMOCOUPLE MEASUREMENTIV1
  • Using a Temperature Sensor for Cold-JunctionCompensations25TEMPERATURECOMPENSATIONCIRCUITTEMPSENSORT2V(T2)T1 V(T1)V(OUT)V(COMP)SAMETEMPMETAL AMETAL BMETAL ACOPPERCOPPERISOTHERMAL BLOCKV(COMP) = f(T2)V(OUT) = V(T1) – V(T2) + V(COMP)IF V(COMP) = V(T2) – V(0°C), THENV(OUT) = V(T1) – V(0°C)TEMPERATURECOMPENSATIONCIRCUITTEMPSENSORT2V(T2)T1 V(T1)V(OUT)V(COMP)SAMETEMPMETAL AMETAL BMETAL ACOPPERCOPPERISOTHERMAL BLOCKV(COMP) = f(T2)V(OUT) = V(T1) – V(T2) + V(COMP)IF V(COMP) = V(T2) – V(0°C), THENV(OUT) = V(T1) – V(0°C)
  • Thermocouple AmplifiersAD849x Product Features and Description Factory trimmed for Type J and K thermocouples Calibrated for high accuracyCold Junction Compensation (CJC) IC temps of 25°C and 60°C Output voltage of 5 mV/°C Active pull-down Rail-to-Rail output swing Wide power supply range +2.7 V to ±15 V Low power < 1 mW typical Package–space saving MSOP-8, lead-free Low cost < $1 in volume Can measure negative temperatures in single-supply operation26Part NumberThermocoupleTypeOptimized TempRangeMeasurement TempRangeInitialAccuracyAD8494 J 0 to 50°C Full J type range ±1°C and ±3°CAD8495 K 0 to 50°C Full K type range ±1°C and ±3°CAD8496 J 25°C to 100°C Full J type range ±1.5°C and ±3°CAD8497 K 25°C to 100°C Full K type range ±1.5°C and ±3°C
  • Demo Using a Temperature Sensor for Cold-Junction Compensations–CN0271Figure 1. K-type thermocouple measurement system with integratedcold junction compensation (simplified schematic: all connectionsnot shown)27AD8495OUTSENSEREF –VS+VS+VS–VSINPINN0.1µF 10µF+5V+2.5VCOLDJUNCTIONCOMPENSATIONTHERMO-COUPLE1MΩ100Ω49.9kΩ0.01µF0.01µF1.0µF100Ω0.1µF 0.1µF10µF+5V +2.5VIN-AMP+OUT–OUTAD847610kΩ10kΩ10kΩ10kΩ100Ω 0.01µF0.01µF1.0µF100Ω SERIALINTERFACEINTERNALCLOCK16-BITADCGNDREFINAD7790DIGITALPGABUFVDDVDDGND+5VADR441+5V+2.5VVIN VOUTGND10598-001
  • High Accuracy ApplicationsThermocouple Cold-Junction CompensationBenefits High accuracy High accuracy, 0.25C, low drift cold junction measurement usingADT7320/7420 Fast throughput Parallel measurement of hot and cold junction gives fastest throughput Flexibility Software-based solutionenabling use of multiplethermocouple types Easy implementation Fully integrated digitaltemp measurementsolution Low cost No costly multipointcold-junction calibrationrequired28
  • High Accuracy Applications CJC using ADT732029ADT7320 for cold-junction temperaturemeasurementThermocoupleisothermalconnectorADT7320mounted onFlex PCBΣ-Δ ADC
  • Temperature Measurement RTD SensorKey application benefits 3-wire RTD 2 matched excitation currents 24-bit ADC resolution 40 nV RMS at gain = 64 Ratiometric configuration 50 Hz and 60 Hz rejection (−75 dB)30RL1RL2RL3RTDGND VDDAD7793SERIALINTERFACEANDCONTROLLOGICINTERNALCLOCKCLKSIGMADELTAADCIOUT1MUXIN-AMPREFIN(+) REFIN(-)BANDGAPREFERENCEGNDSPI SERIALINTERFACEIOVDDVDDGNDIOUT2REFINAIN1RREFEXCITATIONCURRENTS
  • High Impedance SensorsPhotodiodesPiezoelectric sensors Accelerometers HydrophonesHumidity monitorspH monitorsChemical sensorsSmoke detectorsCharge coupled devicesContact image sensors for imaging31
  • Photodiode ApplicationsOptical: light meters, auto focus, flash controlsMedical: CAT scanners (X-ray detection), blood particle analyzersAutomotive: headlight dimmers, twilight detectorsCommunications: fiber optic receiversIndustrial: bar code scanners, position sensors, laser printers32
  • Photodiode Equivalent Circuit33PHOTOCURRENTIDEALDIODEINCIDENTLIGHTRSH(T)100kΩ -100GΩCJNote: RSH halves every 10°C temperature rise
  • Photodiode Modes Of OperationPhotovoltaic Zero bias No “dark" current Linear Low noise (Johnson) Precision applicationsPhotoconductive Reverse bias Has “dark" current Nonlinear Higher noise (Johnson + shot) High speed applications34–+–VBIAS–+
  • Photodiode SpecificationsSilicon Detector Part Number SD-020-12-001Area: 0.2 mm2Capacitance: 50 pFShunt resistance at 25°C: 1000 mWMaximum linear output current: 40 µAResponse time: 12 nsPhotosensitivity: 0.03 µA/foot candle (fc)35
  • Short Circuit Current vs. Light Intensity forPhotodiode (Photovoltaic Mode)36Environment Illumination (fc) Short Circuit CurrentDirect sunlight 1000 30 µAOvercast day 100 3 µATwilight 1 0.03 µAFull moonlit night 0.1 3000 pAClear night/no moon 0.001 30 pA
  • Current-to-Voltage Converter (Simplified)37ISC = 30pA(0.001 fc)+_R = 1000MΩVOUT = 30mVSENSITIVITY: 1mV / pA
  • Preamplifier DC Offset Errors38~VOSIBIBR1R21000MΩ+_IB doubles every 10°C temperature riseR1 = 1000 MΩ at 25°C (diode shunt resistance)R1 halves every 10°C temperature riseDC NOISE GAIN = 1 + R2R1OFFSETRTOR3R3 cancellation resistor not effective
  • 39
  • Photodiode Amplifier Design Choices40
  • Photodiode Amplifier Design Result41
  • Complete Photodiode Sensing ApplicationCN0272Figure 1. Photodiode preamp system with dark currentcompensation (simplified schematic: all connections anddecoupling not shown)42AVDDCFRFRF0.1µF0.1µF3.3pFVBIAS–5V+1.8V+0.9V22pFAD8065SFH 2701AD9629-20VIN–VIN+VCMINPINNVOCM+2.5V+OUT–OUTAD84751kΩ2.5kΩ24.9kΩ24.9kΩ2.5kΩ1kΩ33Ω33Ω+5V–5V+5V–5VTP3TP2ADR441+5V+2.5VVIN VOUTGNDGNDTP110599-001
  • Tweet it out! @ADI_News #ADIDC13Visit the Dual Channel Spectroscopy/ColorimetryDemo Board in the Exhibition Room43Circuit Features Three modulated LED drivers Two photodiode receive channels Programmable gainCircuit Benefits Ease of use Self contained solution Dual channel 16-bit ADC for dataanalysisComplete Design Files■ Schematic■ Bill of Material■ PADs Layout■ Gerber Files■ Assembly DrawingEVAL-SDP-CB1ZEVAL-CN0312-SDPZThis demo board is available for purchase:www.analog.com/DC13-hardware
  • Sensor Resistances Used in BridgeCircuits Span a Wide Dynamic Range44Strain gages 120Ω, 350 Ω, 3500 ΩWeigh scale load cells 350 Ω to 3500 ΩPressure sensors 350 Ω to 3500 ΩRelative humidity 100 kΩ to 10 mΩResistance temperature devices (RTDs) 100 Ω, 1000 ΩThermistors 100 Ω to 10 mΩFor more information and demonstration of bridge sensors, attendthe Instrumentation – Sensing 2 – session.
  • Position and Motion SensorsLinear position: linear variable differential transformers (LVDT)Hall effect sensors Proximity detectors Linear output (magnetic field strength)Rotational position: Optical rotational encoders Synchros and resolvers Inductosyn® sensors (linear and rotational position) Motor control applicationsAcceleration and tilt: accelerometersGyroscopes45
  • 46MEMS Sensors are EverywhereHealth and FitnessProductsSmartphonesAutomotive Safetyand InfotainmentPrecision AgricultureAvionics andNavigationFleet ManagementAssetTracking
  • What you can measure:47
  • What you can measure:48Linear Motion
  • ADI’s Motion Signal Processing ™Enables… Motion Sensing49Fleet managementAlarm systemsMotion control and orientation ofindustrial robotsPrecision agriculture
  • What you can measure:50Tilt
  • 51ADI’s Motion Signal Processing ™Enables… Tilt SensingLevelingHorizon detection in cameras
  • What you can measure:52Vibration & Shock
  • 53ADI’s Motion Signal Processing ™Enables… Shock & Vibration SensingPower tool safety:Shock detectionContact sports & industrial machinery:impact detectionWhite goods:vibration monitoring Predictive maintenance:Vibration monitoring
  • What you can measure:54Rotation
  • 55ADI’s Motion Signal Processing ™Enables… Rotation SensingPlatform/antenna stabilization:Industrial, maritime, avionics, communicationsDigital camera OISAutomotive RolloverDetection
  • Measuring complex motion:56Inertial Measurement Unit
  • 57ADI’s Motion Signal Processing ™Enables… Complex Motion SensingPlatform StabilizationGuidance and trajectory:Mil/AeroDetection of Motion in Free SpacePrecision agriculture
  • Measuring motion58
  • ADI’s Inertial MEMS Sensors:Accelerometers measurelinear motionGyroscopes measurerotation59
  • ADI MEMS SENSORS:A brief history…60
  • MEMS at ADI:In the beginning…Concept began in ~1986Market: airbag sensors
  • A little history…The first airbags used ball-in-tube sensors.Concept began in ~1986Market: airbag sensors
  • A little history…The first airbags used ball-in-tube sensors.Concept began in ~1986Market: airbag sensors
  • MEMS at ADI:In the beginning…Concept began in ~1986Market: airbag sensors1989Demonstrated first working MEMSaccelerometer1991First product samplesADXL50: ADI’s FirstMEMS Device
  • 65How Do Accelerometers Work?StrongM a s sWeakM a s sNo DecelerationM a s s
  • How Do Accelerometers Work?constant
  • 67How Do MEMS Accelerometers Work?Single axis accelerometer in silicon has the same components Left / Right (X-axis)XLeft RightM a s sProof MassSuspensionSpringSuspensionSpringMotion(ca. 1992-1995)
  • How Do iMEMS Accelerometers Work?Single axis accelerometer in silicon has the same components Left/right (x-axis)68(ca. 1992-1995)
  • How Do iMEMS Accelerometers Work?All moving parts are suspended above the substrate Sacrificial layer removed from below moving parts during fabrication69(ca. 1992-1995)
  • 70How Do MEMS Accelerometers Work?Measurement of deflection is done withvariable differential capacitor "finger sets"(ca. 1992-1995)
  • Measuring the Position of the Proof MassSuspensionSpringSuspensionSpringSuspensionSpringSuspensionSpringFinger SetsFinger Sets Finger SetsFinger SetsProofMassSuspensionSpringSuspensionSpringSuspensionSpringSuspensionSpringSuspensionSpringSuspensionSpringSuspensionSpringSuspensionSpringFinger SetsFinger Sets Finger SetsFinger SetsFinger SetsFinger Sets Finger SetsFinger SetsProofMassProofMassXY Differential capacitance used to pick off motion ofmass C1 and C2 is the capacitance between the mass and a set offixed fingers Keep monitoring (C1 – C2) to determine if the mass hasmoved in the X-axisC1 C2
  • Simplified Reader ArchitectureCMOSsensorclockssensorAC(clock domain)GaindemodulatorDC(baseband)Gainconvert backto basebandamplify amplifyexcite
  • What accelerometers measure:73
  • Measuring TiltA = G sinΦAcceleration due to tilt is the projection onto the sensitive axis of the gravityvector.ΦΦGSensitive axisG17mg / ° tiltnear levelmk
  • High Performance AccelerometersIndustry’s Strongest and Most Complete PortfolioLow-gHigh-gADXL103ADXL203ADXL78ADXL213ADXL27812212Two-Pole Bessel FilterPWMOutput±1.7g±1.7g±1.7gADXL3373±3g±35/50/70g±35/50/70g±70/250/500gADXL001120-22KHz BandwidthADIS160062±5g200 μg/√Hz rmsSPITemp SensorADIS160032±1.7g110 μg/√Hz rmsSPITemp Sensor0.1° accuracyTemperature CalibrationProgrammable/Alarms/FilteringADIS16209/3/12±90, ±180gADIS16227/33±70gADIS162042ProgrammableCapture BuffersPeak Sample/Hold±37/70gFunctionSpecificTILT / INCLINOMETEREmbedded FFT/StorageProgrammable Alarm BandsMultiMode OperationVIBRATIONADXL326±16gIMPACTADIS162403±19gProgrammable TriggersEvent Capture BuffersADXL3123AECQ-100Qualified±1.5/3/6/12gUp to 13bit resolution30μA to 140μA power3IMPACTiMEMs XLANALOGiMEMs XLDIGITALiSensor XLDigitalgaxesaxesgaxesgADXL2062±5g+175°C OperationADXL2122±5gADXL3433±2/4/8/16gADXL3443±2/4/8/16gADXL3453±2/4/8/16gADXL3463±2/4/8/16gADXL3623±2/4/8g12bit resolution @ ±2g<2uA power consumptionADXL3773±200gADXL3503Min/MaxTemp Sensitivity±1/2/4/8gFocusing on High Performance with:• Industry Lowest Power Consumption• Industry Best Precision Over Lifetime• Industry Best Temperature Range• Industry Best Sensor/Signal Processing• Industry Best Integration… Performance Under All Conditions
  • Highlight Product:ADXL362: Industry’s Lowest Power MEMS AccelBy far…< 2 µA at 100 Hz in Measurement Mode270 nA in Wake-Up ModeAlso helps save system power Enables Autonomous, Continuously Operational Motion-activated Switch Enhanced Activity/Inactivity Detection Deep FIFO
  • ADI’s Inertial MEMS Sensors:Accelerometers measurelinear motionGyroscopes measurerotation77
  • Gyro Building BlocksWhat does one need?xxxxA Good XL(We already know how to do that)+A gizmo that convertsany rotation to a force+A couplingmechanism thattransfers the forcegenerated by the“gizmo” to theaccelerometer
  • Gyro Building BlocksThe Coriolis Effect: Converting rotationto force since 1835MASSROTATIONOSCILLATIONCORIOLISFORCEWhat is the Coriolis effect?In plain English… a moving mass, when rotated, imparts a force toresist change in direction of motion
  • Gyro Building BlocksxxxxA Good XL(We already know how to do that)+ +A couplingmechanism thattransfers the forcegenerated by the“gizmo” to theaccelerometerMass withvelocity
  • Gyro Building BlocksxxxxCoupling mechanism:Cut a hole in themiddle of XL and dropthe “moving mass”insideMass withvelocity
  • RESONATOR MOTIONGyro Principle of Operation82ACCELEROMETER TETHER RESONATOR TETHERACCELEROMETER FRAMERESONATORCORIOLISACCELERATIONAPPLIED ROTATIONANCHOR
  • Gyro Principle of Operation83No Rotation
  • Gyro Principle of Operation84Rotation Applied
  • How Do Gyros Work?Video showing motion of proof mass85
  • Problems with Single Mass GyrosSingle mass gyros generally cannot differentiate between rotation(which you want to measure) and vibration at the resonantfrequency86
  • Gyro Principle of Operation87Rotation Applied-+ADXRS series design use two beams (masses) resonating in anti-phase (180° out of phase) Shock and vibration is common mode, so differential operation allows rejectionof many errors
  • Gyro Principle of Operation88Vibration Applied-+Cancelled out
  • Photograph of Mechanical Sensor89
  • Problems With Single Mass Gyros……are also problems with dual-mass gyros, just to alesser extent.That wasn’t good enough for us.
  • The Latest
  • High Performance Gyro and IMUIndustry’s Strongest and Most CompletePortfolioRateGradeTacticalGrade> 10 o/hrin-run Stability< 10 o/hrin-run StabilityADXRS45XADIS16265ADXRS646ADXRS6420.015o/s/g5mA6 o/hr16ppm/oC SensitivityADIS1636X /405/7ADIS163056, 9,104ADIS163756ADIS163346ADIS16385612o/hr; 0.13mg Stability0.013o/s/gContinuous Bias Estimation<8cm340ppm/oCADIS16135/36o/hr, YawQuad-Core DesignsIndustry Leading VibrationImmunityADXRS62x/652Vertical MountPackage option25ppm/oC SensitivityiMEMs GyroANALOGiMEMs GyroDIGITALiSensor GyroDigitalIMU(DoF)-X0.03o/s/gADIS16488ADIS16448in development0.015o/s/g1000o/sec range40ppm/oC8cm36 o/hr ; 0.1mg0.009o/s/g6 - 106 - 10Up to 1200o/secADIS161364 o/hr0.18 ARWgoalsADIS-NxGnADXRS-NxGn
  • Highlight Product:ADXRS64x High Performance Gyroscope Series Quad differential sensor technology Pin and package compatible to ADXRS62x family Superb vibration rejection Sensitivity to Linear Acceleration as low as0.015°/s/g Vibration Rectification as low as 0.0001°/s/g2 Various flavors: Bias stability as low as 12°/hour Rate noise density as low as 0.01°/s/√Hz Angular measurement range up to 50,000°/s Startup time as fast as 3 msec Power consumption down to 3.5 mAADXRS64x Gyros FeatureADI’s Unique Quad DifferentialSensor Design
  • MEMS Microphone94Just another accelerometer in disguise
  • Microphone Technology Trends to MEMS Performance is unaffected by Pb-free solder reflow temperature Replaces high cost manual sortingand assembly with automatedassembly Higher SNR and superior matching Higher mechanical shockresistance Wider operating temperature range Consumes less current Superior performance part-to-part,overtemperature, and with vibration95MEMSDIGITAL OUTPUTMEMSANALOG OUTPUTECMJFET
  • ADI Microphone StructureDiaphragm and back plate electrodes form a capacitorSound pressure causes the diaphragm to vibrate and change thecapacitanceCapacitance change is amplified and converted to analog or digitaloutputDIAPHRAGMPERFORATED BACK PLATESPRING SUSPENSIONSENSE GAP
  • Normal conversation:60 dB (or 20 MPa) 0.55 nm (5.5 A)Crying baby:110 dB 170 nm (1700 A)How Much Does ADI MEMS MicrophoneDiaphragm Move?97
  • Why Use MEMS Microphones?Performance DensityElectret mics performance degrades quickly in smaller packagesMEMS mics achieve new level of performance in the same volumeas the smallest electrets!9870dB55dBMicrophone Physical Volume (cubic millimeters)10mm3 100 200 300 400 500 600 700MEMS MICROPHONESELECTRET-BASEDMICROPHONESSNRMEMS MICS SHIFTS THESNR-TO-VOLUME SLOPEUP DRAMATICALLY!
  • Why Use MEMS Microphones?Less Sensitivity Variation vs. TemperatureECM vs. ADMP44199Change (in dB) from original sensitivity
  • Top vs. Bottom Port: Performance ImpactBottom Port Provides Superior SNR &Frequency Response100 All top-port microphones (MEMS and ECM) currently on the market have sharp peaksin their high-frequency response, making them unacceptable for wideband voiceapplications All top-port microphones have low SNR (55…58 dB) There are no top-port microphones with high performance currently on the marketADI Bottom-Port MEMS Microphone Competitor Top-Port MEMS Microphone
  • Industry’s Most Integrated MEMS MicADMP441 integrates more of the signal chain than any other MEMS Mic!Typical analog output mics (ADMP404) integrate an output ampTypical digital output mics (ADMP421) integrate an ADC and provide a single bitoutput stream (known as “pulse density modulation” or PDM) – which still requires afilter and some signal processing and PDM codecs focus on mobile devicesADMP441 provides full I2S output – the most common digital audio interfaceADMP441ADMP421ADMP404SecondaryAmplifierSerializerI2S, etc. Digital SignalProcessor orMicrocontrollerFilter
  • ADI MEMS Microphone PortfolioHigh Performance MEMS MicrophonesADMP441Full I2S-OutputMost integratedmicrophoneavailable!ADMP42161dB SNRPulse DensityModulated (PDM)OutputDigital OutputHigher IntegrationPackage3.35x2.6x0.88 mm4.72x3.76x1 mm4x3x1 mmAnalog OutputFlexibility in Signal AcquisitionADMP40562dB SNR200 Hz to 15 kHz FlatFrequency ResponseADMP401100 Hz to 15 kHz FlatFrequency ResponseADMP52165dB SNRPulse DensityModulated (PDM)OutputADMP40462dB SNR100 Hz to 15 kHz FlatFrequency ResponseADMP50465dB SNR100 Hz to 15kHzFrequency Response65dB SNR Family62dB SNR Family
  • Tweet it out! @ADI_News #ADIDC13What We CoveredSensors are the sourceSensor signals are typically low-level and difficultSignal conditioning is key to high performanceSilicon sensors are integrated with signal conditioningApplications keep demanding higher accuracyMotion sensors with moving silicon elements are drivingsystems in all market areas103
  • Tweet it out! @ADI_News #ADIDC13Design Resources Covered in this SessionDesign Tools and Resources:Ask technical questions and exchange ideas online in ourEngineerZone ® Support Community Choose a technology area from the homepage: ez.analog.com Access the Design Conference community here: www.analog.com/DC13community104Name Description URLPhotodiode Wizard Photodiode/amplifier design tool
  • Tweet it out! @ADI_News #ADIDC13Selection Table of Products Covered Today105Part number DescriptionAD590/592/TMP17 Two-terminal current-out temperature sensorAD849x Thermocouple amplifier w/cold junction compensationADT7320/7420 0.25C accurate digital temperature sensorsAD7793 24-bit ADC with RTD sensor driverADA4638 Photodiode amplifierADXL362 2µA high-resolution digital accelerometerADXRS64X High performance gyroscope seriesADMP404/504 High performance analog microphonesADMP441 Complete digital microphone w/ filter
  • Tweet it out! @ADI_News #ADIDC13Visit the K-Type Thermocouple MeasurementSystem with Integrated Cold-JunctionCompensation (CN0271) in the Exhibition RoomThis is a complete thermocouplemeasurement system with coldjunction compensation for Type K.It includes a 16-bit Ʃ-∆ ADC, cold-junction amplifier, and low noiseinstrumentation amplifier toprovide common-mode rejectionfor long lines.106Image of demo/boardThis demo board is available for purchase:http://www.analog.com/DC13-hardware
  • Tweet it out! @ADI_News #ADIDC13Visit the Tilt Measurement Demo in theExhibition Room107Measure tilt using the ADXL203dual axis accelerometerThis demo board is available for purchase:www.analog.com/DC13-hardwareSDP-S BOARDSOFTWARE OUTPUT DISPLAY EVAL-CN0189-SDPZ