Understanding Smart Sensors - Nomads.usp

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252 Understanding Smart SensorsInput(s)PowerdeviceDiagnosticsControlPowerdevicePowerdeviceLoadProtectionLoadLoadFigure 11.1 Smart-power IC block diagram.devices can provide. One of the key means to achieving increased functionalityis to integrate sensing into the smart-power IC.11.3 Embedded SensingSensing in smart-power ICs detects fault conditions and threshold conditions,which allows implementation of control strategies. Overtemperature, overcurrent,and overvoltage conditions can be sensed, and the smart-power IC can bedesigned to react or simply provide a signal to the MCU for system-safe operation.This section explores the different sensing techniques and applications ofthe sensed signal.11.3.1 Temperature SensingTemperature sensors can be easily produced in semiconductor devices by usingeither the temperature characteristics of base-emitter voltage (V be ) or a diffusedresistor. In addition, circuitry is easily integrated to produce a monolithic temperaturesensor with an output that can be easily interfaced to an MCU. Byusing an embedded temperature sensor, additional features can be added toICs. (Note: A sensor becomes an embedded item in a semiconductor productwhen it has a secondary instead of primary function.)
Mechatronics and Sensing Systems 253Sensing for fault conditions, such as a short circuit, is an integral part ofmany smart-power ICs. The ability to obtain temperature sensors in a mixedbipolar-CMOS-DMOS semiconductor process provides protection and diagnosticsas part of the features of smart-power ICs. The primary function of thepower IC is to provide a microcontroller-to-load interface for solenoids, lamps,and motors. In multiple-output devices, sensing the junction temperatureof each device allows the status of each device to be input to the MCU,and, if necessary, the MCU can shut down a particular unit that has a faultcondition [3].In ICs, the temperature limit can be sensed by establishing a band gap reference.Two diodes’ junctions are biased with different current densities, butthe ratio is essentially constant over the operating temperature range (−40°Cto150°C). The following equation shows how the differential voltage (∆V be )isrelated to the current (I ) and emitter area (A) of the respective transistors:I1 A1Vbe 1− Vbe 2= Vbe = [ kBT q]⋅⎛ /⎜⎞∆ / ln ⎟⎝ I2/A2⎠(11.1)where k B is Boltzman’s constant (1.38 ⋅ 10 −23 J/K), T is the temperature in K,and q is the charge of an electron (1.6 ⋅ 10 −19 C).At a targeted high temperature, the negative temperature coefficient of V beequals the positive temperature coefficient voltage developed across a senseresistor, and a thermal limit signal is generated. Other circuitry regulates thevoltage and turns off the output power device.A smart-power IC can have multiple power drivers integrated on a singlemonolithic piece of silicon. Each driver can have a temperature sensor integratedto determine the proper operating status and shut off only a specificdriver if a fault occurs. Figure 11.2 shows an eight-output driver that independentlyshuts down the output of a particular driver if its temperature is excessive(between 155 and 185°C).The octal serial switch (OSS) adds thermal sensing through overtemperature-detectioncircuitry to the protection features. Faults can be detectedfor each output device and individual shutdown can be implemented. In amultiple-output power IC, it is highly desirable to shut down only the devicethat is experiencing a fault condition and not all the devices that are integratedon the power IC. With outputs in various physical locations on the chip, it isdifficult to predict the thermal gradients that could occur in a fault situation.Local temperature sensing at each output, instead of a single global temperaturesensor, is required.
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Understanding Smart SensorsSecond E
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Library of Congress Cataloging-in-P
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ContentsPrefacexix1 Smart Sensor Ba
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Contentsix3.3.3 Hall Effect 603.3.4
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Contentsxi5.8 Summary 116References
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Contentsxiii8.3.1 Surface Acoustica
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Contentsxv11.1.1 Integration and Me
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Contentsxvii14.4.4 Electrostatic Me
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PrefaceThe number one challenge fac
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Prefacexxifor well over 6 years. A
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2 Understanding Smart Sensorsobserv
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4 Understanding Smart Sensorssmart
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6 Understanding Smart Sensorsto pro
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8 Understanding Smart Sensorsinclud
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28 Understanding Smart SensorsSacri
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30 Understanding Smart Sensors2.4.3
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32 Understanding Smart Sensorsmeasu
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38 Understanding Smart SensorsTable
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42 Understanding Smart SensorsAlumi
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44 Understanding Smart SensorsThe f
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46 Understanding Smart Sensors[21]
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The Nature of Semiconductor Sensor
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4Getting Sensor Information Into th
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5Using MCUs/DSPs to Increase Sensor
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Using MCUs/DSPs to Increase Sensor
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6Communications for Smart SensorsBe
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7Control TechniquesA machine is int
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Control Techniques 151Table 7.1Type
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Control Techniques 153otherwise tak
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Control Techniques 155consisting of
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Control Techniques 157Supplied byap
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Control Techniques 159InputX1Synaps
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Control Techniques 1617.6 Adaptive
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Control Techniques 163ObserverHB−
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Control Techniques 165linear-vector
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Control Techniques 1677.7.2 Combine
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Control Techniques 169Domain-type s
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Control Techniques 171[19] De Silva
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8Transceivers, Transponders, andTel
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Transceivers, Transponders, and Tel
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Page 223 and 224: 9MEMS Beyond Sensors“And these ot
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Page 319 and 320: 13The Implications of Smart SensorS
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The Implications of Smart Sensor St
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14The Next Phase of Sensing Systems
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The Next Phase of Sensing Systems 3
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List of Acronyms and Abbreviations3
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List of Acronyms and Abbreviations
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Glossaryablationvaporization of mat
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Glossary 353buscalibrationconnectio
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Glossary 355end point straight line
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Glossary 357data transmission and p
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Glossary 359multiplexer device that
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Glossary 361repeatability the maxim
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Glossary 363spread spectrum techniq
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Glossary 365transducer a device con
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Selected BibliographyBooks and Jour
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Selected Bibliography 369Northeaste
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Selected Bibliography 371Miscellane
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About the AuthorRandy Frank is a te
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Index4-to 20-mA signal transmitter,
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Index 377definitions, 119-20introdu
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Index 379HVAC, 318-19MCU with integ
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Index 381Linearization, 108Linear p
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Index 383in chemical measurements,
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Index 385Ratiometricity, 56Reactive
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Index 387IC fabrication, 19micromec
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Index 389Transducer-independent int
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