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Class 1: The Fundamental of Designing with Semiconductors
The document provides an overview of high-performance signal processing solutions, detailing the processes from capturing real-world signals to electronic output. It covers different sensor types, their characteristics, and applications in temperature measurement, position sensing, and motion detection. Additionally, it includes specifics about thermocouples, semiconductor sensors, and introduces upcoming webcasts related to sensor fundamentals and conversion technologies.
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Class 1: The Fundamental of Designing with Semiconductors
- 1. The World Leaderin High Performance Signal Processing Solutions FUNDAMENTALS OF DESIGN Class 1 Introduction Presented by David Kress
- 2. The Goal Capturewhat is going on in the real world Convert into a useful electronic format Analyze, Manipulate, Store, and Send Return to the real world
- 3. The real worldis NOT digital
- 4. Analog to Electronicsignal processing Sensor Amp Converter Digital Processor (INPUT) Actuator Amp Converter (OUTPUT)
- 5. The Sensor Analog, but Analog Sensor NOT (INPUT) AND Amp Converter Digital Processor electronic electronic Actuator Amp Converter (OUTPUT)
- 6. Popular sensors Sensor Type Output Thermocouple Voltage Photodiode Current Strain Gauge Resistance Microphone Capacitance Touch Button Charge Output Antenna Inductance
- 7. Thermocouple Very low level (µV/ºC) Non-linear Difficult to handle Wires need insulation Susceptible to noise Fragile
- 8. Sensor Signal Conditioning Sensor Amp Analog, Analog, electronic, electronic, but “dirty” and “clean” •Amplify the signal to a noise-resistant level •Lower the source impedance •Linearize (sometimes but not always) •Filter •Protect
- 9. Types of TemperatureSensors THERMOCOUPLE RTD THERMISTOR SEMICONDUCTOR Widest Range: Range: Range: Range: –184ºC to +2300ºC –200ºC to +850ºC 0ºC to +100ºC –55ºC to +150ºC High Accuracy and Fair Linearity Poor Linearity Linearity: 1ºC Repeatability Accuracy: 1ºC Needs Cold Junction Requires Requires Requires Excitation Compensation Excitation Excitation Low-Voltage Output Low Cost High Sensitivity 10mV/K, 20mV/K, or 1µA/K Typical Output
- 10. Common Thermocouples TYPICAL NOMINAL ANSI JUNCTION MATERIALS USEFUL SENSITIVITY DESIGNATION RANGE (ºC) (µV/ºC) Platinum (6%)/ Rhodium- 38 to 1800 7.7 B Platinum (30%)/Rhodium Tungsten (5%)/Rhenium - 0 to 2300 16 C Tungsten (26%)/Rhenium Chromel - Constantan 0 to 982 76 E Iron - Constantan 0 to 760 55 J Chromel - Alumel –184 to 1260 39 K Platinum (13%)/Rhodium- 0 to 1593 11.7 R Platinum Platinum (10%)/Rhodium- 0 to 1538 10.4 S Platinum Copper-Constantan –184 to 400 45 T
- 11. Thermocouple Output Voltages forType J, K and S Thermocouples THERMOCOUPLE OUTPUT VOLTAGE (mV) 60 50 TYPE K 40 TYPE J 30 20 TYPE S 10 0 -10 -250 0 250 500 750 1000 1250 1500 1750 TEMPERATURE (°C)
- 12. Thermocouple Seebeck Coefficientvs. Temperature 70 60 TYPE J SEEBECK COEFFICIENT - µV/ °C 50 TYPE K 40 30 20 TYPE S 10 0 -250 0 250 500 750 1000 1250 1500 1750 TEMPERATURE (°C)
- 13. Thermocouple Basics A. THERMOELECTRIC VOLTAGE C. THERMOCOUPLE MEASUREMENT Metal A Metal A V1 – V2 Metal A V1 T1 Thermoelectric V1 T1 T2 V2 EMF Metal B Metal B B. THERMOCOUPLE D. THERMOCOUPLE MEASUREMENT Copper Copper Metal A R Metal A V Metal A Metal A I T3 T4 V1 T1 T2 V2 V1 T1 T2 V2 Metal B Metal B R = Total Circuit Resistance I = (V1 – V2) / R V = V1 – V2, If T3 = T4
- 14. Using a TemperatureSensor for Cold- Junction Compensations V(OUT) TEMPERATURE V(COMP) COMPENSATION CIRCUIT COPPER COPPER METAL A SAME METAL A TEMP TEMP SENSOR T1 V(T1) V(T2) T2 METAL B V(COMP) = f(T2) ISOTHERMAL BLOCK V(OUT) = V(T1) – V(T2) + V(COMP) IF V(COMP) = V(T2) – V(0°C), THEN V(OUT) = V(T1) – V(0°C)
- 15. AD594/AD595 Monolithic Thermocouple Amplifierwith Cold-Junction Compensation +5V 0.1µF BROKEN 4.7k THERMOCOUPLE VOUT ALARM 10mV/°C OVERLOAD TYPE J: AD594 DETECT TYPE K: AD595 THERMOCOUPLE AD594/AD595 +A – – –TC ICE G + G POINT + + COMP +TC
- 16. Basic Relationships ForSemiconductor Temperature Sensors IC IC N TRANSISTORS ONE TRANSISTOR VBE VN kT IC kT IC VBE ln VN ln q IS q N IS kT VBE VBE VN ln(N) q INDEPENDENT OF IC, IS
- 17. Classic Bandgap TemperatureSensor +VIN R R "BROKAW CELL" + VBANDGAP = 1.205V I2 @ I1 Q2 Q1 NA A VN VBE kT VBE VBE VN ln(N) R2 (Q1) q R1 kT VPTAT = 2 ln(N) R2 q R1
- 18. Analog Temperature Sensors Product Accuracy Max Accuracy Operating Supply Max Interface Package (Max) Range Temp Range Current Range ± 0.5°C 25°C -55°C to TO-52,2-ld FP, AD590 4 to 30V 298uA Current Out ± 1.0°C -25°C to 105°C 150°C SOIC, Die ± 0.5°C 25°C -25°C to 298uA AD592 4 to 30V Current Out TO-92 ± 1.0°C -55°C to 150°C 105°C 0°C to 85°C -55°C to TO-92, SOT23, TMP35 ± 2.0°C 2.7 to 5.5V 50uA Voltage Out -25°C to 100°C 150°C SOIC TO-92, SOT23, -40°C to 125°C -55°C to 50uA TMP36 ± 3.0°C 2.7V to 5.5V Voltage Out SOIC 150°C ± 2.0°C -50°C to 150°C -50°C to AD22100 4 to 6.5V 650uA Voltage Out TO-92, SOIC, Die 150°C ± 2.5°C 0°C to 100°C 0°C to 100°C AD22103 2.7 to 3.6V 600uA Voltage Out TO-92, SOIC
- 19. Digital Temperature Sensors ComprehensivePortfolio of Accuracy Options Product Accuracy (Max) Max Accuracy Interface Package Range ± 0.2°C -10°C to 85°C ADT7420/7320 I2C/SPI LFCSP ± 0.25°C -20°C to 105°C ADT7410/7310 ± 0.5°C -40°C to 105°C I2C/SPI SOIC ± 1°C (B grade) 0°C to 85°C ADT75 I2C MSOP, SOIC ± 2°C (A grade) -25°C to 100°C ± 1°C 0°C to 70°C ADT7301 SPI SOT23, MSOP ± 1°C 0°C to 70°C TMP05/6 PWM SC70, SOT23 ± 1.5°C -40°C to 70°C AD7414/5 I2C SOT23,MSOP ADT7302 ± 2°C 0°C to 70°C SPI SOT23,MSOP ± 4°C TMP03/4 -20°C to 100°C PWM TO-92,SOIC,TSSOP 21
- 20. Position and MotionSensors 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 Inductosyns (Linear and Rotational Position) Motor Control Applications Acceleration and Tilt: Accelerometers Gyroscopes
- 21. + THREADED CORE VA ~ VOUT = VA – VB AC SOURCE VB 1.75" _ VOUT VOUT SCHAEVITZ _ POSITION + _ POSITION + E100 LVDT – Linear Variable Differential Transformer
- 22. AD698 EXCITATION AMP ~ REFERENCE OSCILLATOR B VB + A VOUT FILTER AMP B A VA A, B = ABSOLUTE VALUE + FILTER _ 4-WIRE LVDT AD698 LVDT Signal Conditioner
- 23. Hall Effect Sensors T CONDUCTOR OR SEMICONDUCTOR I I VH I = CURRENT B B = MAGNETIC FIELD T = THICKNESS VH = HALL VOLTAGE
- 24. AD22151 Linear OutputMagnetic Field Sensor V / 2 V = +5V CC CC VCC / 2 R2 + R1 TEMP REF _ R3 _ AD22151 VOUT + OUTPUT AMP CHOPPER AMP VOUT = 1 + R3 0.4mV Gauss NONLINEARITY = 0.1% FS R2
- 25. Accelerometer Applications Tiltor Inclination Car Alarms Patient Monitors Cell phones Video games Inertial Forces Laptop Computer Disc Drive Protection Airbag Crash Sensors Car Navigation systems Elevator Controls Shock or Vibration Machine Monitoring Control of Shaker Tables ADI Accelerometer Fullscale g-Range: ± 2g to ± 100g ADI Accelerometer Frequency Range: DC to 10kHz
- 26. ADXL-family Micro-machined Accelerometers AT REST CS1 CS2 APPLIED ACCELERATION CENTER PLATE TETHER BEAM CS1 CS1 = CS2 < CS2 FIXED OUTER PLATES DENOTES ANCHOR
- 27. Using an Accelerometerto Measure Tilt +90° X X 1g Acceleration 0° –90° +1g Acceleration = 1g × sin 0g –90° 0° +90° –1g
- 28. Gyro Axes ofRotational Sensitivity
- 29.
- 30. Displacement due tothe Coriolis Effect
- 31. Photograph of mechanicalsensor.
- 32. High Impedance Sensors Photodiodes Piezoelectric Sensors Accelerometers Hydrophones Humidity Monitors pH Monitors Chemical Sensors Smoke Detectors Charge Coupled Devices and Contact Image Sensors for Imaging
- 33. Photodiode Equivalent Circuit INCIDENT LIGHT PHOTO RSH(T) CURRENT CJ IDEAL DIODE 100k - 100G NOTE: RSH HALVES EVERY 10 C TEMPERATURE RISE
- 34. Current-to-voltage Converter (Simplified) R = 1000M ISC = 30pA (0.001 fc) _ VOUT = 30mV + Sensitivity: 1mV / pA
- 35. Preamplifier DC OffsetErrors 1000M R2 IB ~ _ OFFSET VOS RTO R1 IB + R3 DC NOISE GAIN = 1 + R2 R1 IB DOUBLES EVERY 10 C TEMPERATURE RISE R1 = 1000M @ 25 C (DIODE SHUNT RESISTANCE) R1 HALVES EVERY 10 C TEMPERATURE RISE R3 CANCELLATION RESISTOR NOT EFFECTIVE
- 36. Sensor Resistances UsedIn Bridge Circuits Span A Wide Dynamic Range Strain Gages 120, 350, 3500 Weigh-Scale Load Cells 350 - 3500 Pressure Sensors 350 - 3500 Relative Humidity 100k - 10M Resistance Temperature Devices (RTDs) 100 , 1000 Thermistors 100 - 10M
- 37. Wheatstone Bridge ProducesAn Output Null When The Ratios Of Sidearm Resistances Match VB THE WHEATSTONE BRIDGE: R4 R3 R1 R2 VO VB R1 + R4 R2 + R3 VO AT BALANCE, R1 R2 VO = 0 if R4 R3 R1 R2
- 38. Output Voltage SensitivityAnd Linearity Of Constant Current Drive Bridge Configurations Differs According To The Number Of Active Elements IB IB IB IB R R R+R R R RR R+R RR VO VO VO VO R R+R R R+R R R+R RR R+R R VO: IBR R IB R IB R IB R 4 R + 2 2 4 Linearity 0.25%/% 0 0 0 Error: (A) Single-Element (B) Two-Element (C) Two-Element (D) All-Element Varying Varying (1) Varying (2) Varying
- 39. A Generally PreferredMethod Of Bridge Amplification Employs An Instrumentation Amplifier For Stable Gain And High CMR VB OPTIONAL RATIOMETRIC OUTPUT VREF = VB +VS R R R VB VOUT = R GAIN 4 R + RG 2 IN AMP REF VOUT + R R+R -VS* * SEE TEXT REGARDING SINGLE-SUPPLY OPERATION
- 40. Upcoming webcasts Converter Simulation: Beyond the Eval Board January 19th at 3:00 p.m. (ET) RF Detectors February 16th at Noon (ET) Challenges in Embedded Design for real-time systems March 16th at Noon (ET) www.analog.com/webcast
- 41. Fundamentals Webcasts 2011 January Introduction and Fundamentals of Sensors February The Op Amp March Beyond the Op Amp April Converters, Part 1, Understanding Sampled Data Systems May Converters, Part 2, Digital-to-Analog Converters June Converters, Part 3, Analog-to-Digital Converters July Powering your circuit August RF: Making your circuit mobile September Fundamentals of DSP/Embedded System design October Challenges in Industrial Design November Tips and Tricks for laying out your PC board December Final Exam, Ask Analog Devices www.analog.com/webcast
Editor's Notes
- #4 As you probably know, our first challenge is that light, sound, weight, speed, temperature, even smell are analog, or continuous wave forms. That’s okay for us analog human beings, but a lousy format for electronic devices.It gets worse, because those real world analog signals aren’t electronic, either.That means we have two challenges: One is to capture the physical attributes and signals from the real world – these analog signals, and Two, convert them to electronic signals that we can manipulate…
- #5 How we do that is what we’ll be covering in this 12-part course. In the coming months we’ll go through each stage of the basic signal chain, from amplifiers to data converters – those components that convert the analog electronic signal into a digital stream – then to the heart of many modern circuits, the digital processor. We’ll also cover what is needed to power today’s circuits, how to make them portable, and how to lay them out .So let’s go back to the beginning of the circuit and address the first task of turning that analog, non electrical signal into an analog electrical one. How do we do that?
- #6 By employing sensors. Sensors are devices that respond to changes in these analog, non-electronic signals – temperature, speed, weight, pressure, and so on and turn them into electronic analog signals. Those signals can be in many different forms.
- #7 As you can see, for the measurement of different kinds of analog real-world signals, different sensors provide different outputs. In all cases, we have achieved goal number one – capturing that signal so we can move it down the signal chain.
- #8 Let’s look at one example of a sensor. The Thermocouple is a device made of dissimilar metals welded at one end, which generate a voltage that increases with temperature. The output, as we just saw, is a varying voltage. Like any electronic device and like any sensor, it has its benefits and its problems, most important to our goal is that the output of this device is very low level – which means the signal can be below the ambient noise level of the circuit – which in turn means we cannot discriminate it from the noise.
- #9 Which means we need to take that low-level, fragile signal and perform Sensor Signal Conditioning. In this critical step we will:Amplify the signal to a noise-resistant levelLower the source impedanceLinearize (sometimes but not always)FilterProtectionThe result is a signal clean enough to be sent to the converter for digitizing. Without this critical stage data conversion would be inaccurate, rendering the entire circuit useless. It’s that important.
- #17 A series of thermocouple amplifiers is available from Analog Devices so you can find the right accuracy and operating temperature range for your needs. These products use very little power, less than 1mW, and are in a small MSOP package. Two of the important things to look at when using a thermocouple amplifier are the initial accuracy and the temperature range where the amplifier is accurate. This is the temperature of the board that the amplifier is on, not the temperature of the thermocouple itself.
- #43 Before Dave takes any questions, I want to remind you that every month Analog Devices presents a webcast on a current Hot Topic in designing with Semiconductors. A week from today at 3pm, on January 19th, we’ll present a webcast on software simulation for data converters. Next month we’ll be presenting a webcast on the use of RF Detectors and in March on Embedded Design. Registration will be available shortly for both at www.analog.com slash webcast, where you can also access our library of archived webcasts that you can view anytime, on demand.