Circuits from the Lab Reference Designs Linear and Angular Position and Velocity About Circuits from the Lab Reference Designs Circuit from the Lab ® Reference Designs are built and tested for function and performance by Analog Devices applications experts, and are commonly used in analog signal chain design as standalone solutions or to build more complex circuits and subsystems. These proven reference designs support quick and easy evaluation, prototyping, and design integration, and offer: • Comprehensive documentation • Complete design and integration files • Factory tested evaluation hardware ADI’s Circuits from the Lab library has over 200 built and tested reference designs, supporting a wide range of industry segments and applications. Linear and Angular Position and Velocity Application Introduction Sensing and measurement of linear and angular position and velocity is required in a variety of industrial, motor control, medical, avionics, and other applications. For instance, in motor control, the rotor angle (measured in degrees) and velocity (measured in revolutions per second) is converted into digital format, where processing algorithms generate PWM outputs that accurately and efficiently control the motor operation. In avionics, accurate angular and linear position measurements are required to control the ailerons, flaps, tail, and other critical flight mechanisms. The same concepts apply to the field of robotics, where angular and linear position measurements are needed to control the movement of levers, arms, motor drives, and steering mechanisms. In healthcare, angular and linear position sensing is used in laparoscopic surgery, and motion sensors find wide application in vital signs monitoring devices. Accuracy requires an appropriate sensor and signal conditioning circuitry. The most popular sensor types used to perform these functions are electronic and electromechanical such as MR (magnetoresistive), resolvers, MEMS (microelectromechanical systems) accelerometers, LVDTs (linear variable differential transformers), and ultrasonic. Signal conditioning circuitry (typically a combination of ADC, voltage reference, input drive amplifier, instrumentation amplifier, multiplexer, and/or power supply) converts sensor output into a digital format that can be interpreted and processed. Design Considerations — Choosing the Appropriate Sensor and Signal Conditioning Circuitry Magnetoresistive (MR) noncontact sensors are popular because of their low cost and high sensitivity compared to Hall effect sensors. They consist of two Thermalloy bridges oriented 45° from each other that are subjected to a magnetic field. The bridge resistors change value with respect to the orientation of the magnetic field, thereby producing a proportional output voltage. The sensors can be optimized to measure either angular position or linear position. Instrumentation amplifiers are generally used to convert the differential signal from the bridge into a signal compatible with the input range of the ADC. SAR ADCs are easy to use and are widely available in many different resolutions, package types, and power dissipations suitable for most any MR sensor application. They are also easy to interface with analog multiplexers for use in multichannel applications, and there is no pipeline delay as with ∑-∆ ADCs. www.analog.com/circuits-from-the-lab Electromechanical resolvers convert rotational position and velocity into sine and cosine outputs when the excitation winding is driven with a sinusoidal signal. The outputs are processed with a special type of ADC called a resolver-to-digital converter (RDC). An RDC is a tracking converter that is optimized to process the outputs of the resolver and convert the angular position and velocity information from the resolver into digital format. MEMS-based accelerometers produce outputs proportional to acceleration. Dual-axis low g accelerometers are useful in angular measurements where operation over a full 360° is required. MEMS accelerometers also measure vibration or motion. Precision op amps are used to provide the required gain and level shifting. SAR ADCs, popular for the same reasons previously stated, then provide the analog-to-digital conversion. The linear variable differential transformer (LVDT) is also a highly reliable position measurement sensor because the magnetic core can move without friction and does not touch the inside of the tube. Therefore, LVDTs are suitable for flight control feedback systems, position feedback in servomechanisms, automated measurement in machine tools, and many other industrial and scientific electromechanical applications where long-term reliability is important. LVDTs are driven with sine waves, and their outputs are often processed with ICs that are optimized to extract the position information from the LVDT signals. SAR ADCs are then used to provide the digital output as in the case of MR and MEMS applications. Ultrasonic techniques are popular in making distance measurements, such as in level sensing applications. The time between the transmitted and reflected ultrasonic signal is measured using the timer in a microprocessor and then converted into distance based on the speed of sound at the temperature of the measurement environment. The transmitter is controlled using the PWM output of a microprocessor, and the receiver is composed of several op amp stages to provide the required gain, followed by a window comparator to detect the presence of the reflected signal. In addition to the choice of sensor and signal conditioning components selected for the final design, achieving required performance levels depends on giving careful attention to layout, grounding, and decoupling techniques. All Circuits from the Lab Reference Designs have a complete set of downloadable documentation including schematics, PCB layouts, Gerber files, and bill of material to help guide the design engineer during the system design phase. The “Learn More” section of each circuit note contains additional useful references including application notes, tutorials, and technical articles. Hardware is available for purchase to evaluate circuit performance, prototyping, and/or design integration. Circuits from the Lab Reference Designs provide a costeffective tool in achieving optimum designs with minimal risk. Linear and Angular Position and Velocity Circuits from the Lab Reference Designs Reference Design CN0323 CN0341 CN0332 Sensor Type MR MR MR CN0276 Resolver CN0192 Resolver CN0189 CN0303 Measurement Input Range Resolution Output Data Angular position Linear position Rotation speed Angular position, rotation velocity Angular position, rotation velocity 0° to 180° 0" to 1" 0 rps to 1M rps 0° to 360,° 0 rps to 3125 rps 0° to 360,° 0 rps to 3125 rps 12 bits 12 bits N/A SPI SPI Pulse 10 bits to 16 bits SPI 10 bits to 16 bits SPI MEMS Tilt 0° to 360° 12 bits SPI MEMS Vibration ±70 g, ±250 g, ±500 g 12 bits SPI Switch closure SPI SPI LCD display CN0274 MEMS Motion ±2 g, ±4 g, and ±8 g N/A CN0288 CN0301 CN0343 LVDT LVDT Ultrasonic Linear position Linear position Linear position ±0.1" ±0.1" 50 cm to 10 m 12 bits 12 bits 2 cm Special Features Integrated high voltage driver Dual-axis accelerometer Low power, standalone Standalone Evaluation Hardware Pricing (ea) EVAL-CN0323-SDPZ* EVAL-CN0341-SDPZ* EVAL-CN0332-PMDZ** $75.00 $75.00 $35.00 EVAL-CN0276-SDPZ* $130.00 EVAL-AD2S1210EDZ* $99.00 EVAL-CN0189-SDPZ* $60.00 EVAL-CN0303-SDPZ* $70.00 EVAL-CN0274-SDPZ* $50.00 EVAL-CN0288-SDPZ*** EVAL-CN0301-SDPZ*** EVAL-CN0343-EB1Z $110.00 $125.00 $115.00 *Requires additional evaluation control board. **Requires additional evaluation control board and pmod to sdp interposer board. ***Requires additional evaluation control board and measurements specialties LVDT sensor. Highlighted Circuits from the Lab Reference Designs 3.3V 5V THIRD-ORDER BUTTERWORTH LOW-PASS FILTER 5V 5V VDRIVE DVDD AVDD EXC 1 AD8692 2 VCC 1 AD8692 2 EXC 1 AD8397 2 1 AD8397 2 SIN SINLO RESOLVER R1 S2 VREF 2.5V S4 0.1𝛍F 10𝛍F 2.96k𝛀 COSLO DGND 1 AD8694 4 1 AD8694 4 3.3V AD8227 DVDD AVDD AD8615 REFSEL RANGE 1 AD8694 4 5V –VO1 +VO2 SIN –VO2 REF 2.96k𝛀 AD7866 2.5V AD8227 AD8615 DCAPA 470nF AGND THIRD-ORDER BUTTERWORTH LOW-PASS FILTER | Circuits from the Lab Reference Designs 2 CS VB1 DGND AGND COS CN0276: High performance, 10-bit to 16-bit resolver-to-digital converter. DOUTA 5V 1 AD8694 4 1 AD8694 4 SDP VDRIVE VA1 SCLK +VO1 GND1 COS 10𝛍F 5V S3 1 AD8694 4 AA747 1 AD8694 4 0.1𝛍F 2.5V VCC 5V 1 AD8694 4 5V REF S1 5V 5V θ v(t) R2 AD2S1210 VREFOUT 5V v(t) = A sin𝛚t CN0323: Magnetoresistive angle measurement. DCAPB 470nF VREF 100nF 5V AD8615 2.5V Key Products MEMS Accelerometers Part Number ADXL203 ADXL001 ADXL362 Number of Axes 2 1 3 Range (g) Sensitivity (mV/g) ±1.7, ±5, ±18 ±70, ±250, ±500 ± 2, ±4, ±8 1000, 312, 100 16, 4.4, 2.2 1, 2, 4 Self Resonant Frequency (kHz) 5.5 22 3.5 Output Type Noise Density (𝛍g/√Hz) Analog Analog Digital 110 4000 175 Supply Voltage Supply Current (V) (mA) 3 to 6 3.135 to 6 1.6 to 3.5 Package 0.7 2.5 1.8 µA LCC LCC LGA LVDT Signal Conditioners Part Number AD598 AD698 Excitation Frequency (Hz) 20 to 20,000 20 to 20,000 Excitation Voltage Amplitude (V rms) 1.2 to 20 1.2 to 21.2 Excitation Current (mA rms) 40 40 Output Signal Range (V) ±11 ±11 Input Voltage Range (V rms) 0.1 to 3.5 0.1 to 3.5 Supply Voltage Range (V) ±13; 0 to 17.5 ±13; 0 to 17.5 Package SOIC PLCC Resolver-to-Digital Converter Part Number Resolution (Bits) AD2S1210 Max Tracking Rate (rps) 3125, 1250, 625, 156.25 10, 12, 14, 16 Accuracy (Arc Minutes) Reference Frequency (kHz) Velocity Output R/D Interface Supply Voltage (V) Power Dissipation (mW) Package ±2.5 2 to 20 Yes Parallel or serial 5 245 LQFP SAR Analog-to-Digital Converters Part Number Resolution (Bits) Number of Channels Full Power BW (MHz) Throughput Rate Max (kSPS) Package 12 12 12 12 2 1 2 4 2.5 13.5 11 12 125 1000 121 1000 MSOP, SOIC SOT-23 MSOP TSSOP AD7887 AD7476 AD7992 AD7866 Instrumentation Amplifier Part Number AD8227 Gain Min Gain Max Min CMRR @ 60 Hz, G = 5 (dB) VSUPPLY Span Min (V) VSUPPLY Span Max (V) Voltage Noise RTI (𝛍V p-p) Supply Current (𝛍A) Package 5 1000 90 2.2 36 1.5 400 MSOP, SOIC Operational Amplifiers Part Number Small Signal Bandwidth (MHz) Slew Rate (V/𝛍s) Input Offset Voltage Typ (𝛍V) Amplifiers Per Package VSUPPLY Span Min (V) VSUPPLY Span Max (V) Rail-to-Rail Input/Output Supply Current per Amplifier (mA) AD8615 23 12 80 1 2.7 6 Input, output 2 AD8027 ADA4897-2 AD8662 AD8397 AD8692 AD8605 190 230 4 69 69 10 100 120 3.5 53 53 5 200 28 30 1000 400 80 1 2 2 2 2 1 2.7 3 5 3 3 2.7 12 10 16 24 24 6 Input, output Output Output Output Output Input, output 6.5 3 1.4 8.5 0.95 1.2 AD8606 10 5 80 2 2.7 6 Input, output 1.2 AD8608 10 5 80 4 2.7 6 Input, output 1.2 Package SOIC, MSOP, TSOT, TSSOP SOIC, SOT-23 MSOP SOIC, MSOP SOIC, SOIC-EP SOIC, MSOP SOT-23, WLCSP SOIC, MSOP, WLCSP SOIC, TSSOP High Speed Comparator Part Number ADCMP601 Comparators Per Package 1 Propagation Delay (ns) Power Dissipation (mW) 3 10 Supply Voltage (V) 2.5 to 5.5 Input Range (V) Input Latch −0.2 to VCC + 0.2 Yes Adjustable Hysteresis Yes Logic Output Package TTL/CMOS SC70 SPST Power Switch Part Number VIN Min (V) VIN Max (V) Max Switch Current (A) Switch RDSON (m𝛀) Shutdown Current (𝛍A) Ground Current (𝛍A) Enable Logic (V) ADP195 1.1 3.6 1.1 100 @ 1.2 V 0.7 1 1.2 to 3.3 Output tON Delay (𝛍s) 5 Package WLCSP, LFCSP www.analog.com/circuits-from-the-lab | 3 Additional Design Resources Technical Books and Articles • Linear Design Handbook—www.analog.com/library/analogdialogue/archives/43-09/linear_circuit_design_handbook.html • Sensors (Chapter 3) • Data Converters (Chapter 6) • “Which ADC Architecture Is Right for Your Application?” Analog Dialogue— www.analog.com/library/analogdialogue/ archives/39-06/architecture.html Tutorials • MT-021: Successive Approximation ADCs—www.analog.com/MT-021 • MT-030: Resolver-to-Digital Converters—www.analog.com/MT-030 • MT-031: Grounding Data Converters—www.analog.com/MT-031 • MT-101: Decoupling Techniques—www.analog.com/MT-101 Design Tools and Forums • Signal Chain Designer™ Advanced Selection and Design Environment—www.analog.com/signalchaindesigner • EngineerZone™ Online Technical Support Community—ez.analog.com Customer Interaction Center Email North America: [email protected] Europe: [email protected] Asia: [email protected] EngineerZone ez.analog.com Analog Devices, Inc. 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