Texas Instruments Sensing Technologies

Transcription

1 Ambient Broad Spectrum IC Sensors AFEs Current & Power Texas Instruments Sensing Technologies Imaging & Light Current & Power System Protection & Monitoring Op Amp Current Shunt Amp Instrumentation Amp Difference Amp Isolated Amp / ADC Current & Power Position Current & Power Current & Power Ultrasonic Capacitive

2 Why Measure Temperature? Protection Monitor/Control Compensation Instant notification of when a system has cross a thermal limit to prevent damage or maintain safety Monitor the temperature of the system and take appropriate action Compensation for temperature sensitive sensors & applications Examples: Motor Control Lighting & Signage USB Chargers Batteries Charging Perishable Goods Computing Automotive Examples: Optimizing Fan Speed Refrigeration HVAC & Thermostats Industrial control Modulating System Clock Frequency Examples: Gas & Flow Meters CMOS Image Sensors LED Color Correction Optical & Ultrasonic Position Sensors

3 Performance 1 o C Accuracy 4 o C Accuracy Protection System protection from damage due to over / under temperature conditions Things to consider: Hysteresis Easy of programmability Accuracy tradeoff: Sacrificing performance Processor speed, charging speed, early motor shutdown Overdesigning to maintain performance Larger FETs, increased cooling, higher efficiency components Thermal design limit Safety margin 3 o C of lost performance Measurement Error 3

4 Monitoring Knowing the health of your system throughout its operation allows for better system performance and control System Monitoring Advantages Closed loop feedback Self-diagnostics & predictive maintenance Easily store data on internal memory or in the cloud (IoT) Manage the Quality of Goods Cold Chain Tracking temperature sensitive goods in shipment & storage Monitor harsh external conditions Examples Computing Thermostats & HVAC Field transmitters Displays & signage Refrigeration Metering

5 Vout (volts) Temperature Compensation Correcting for temperature drift of other system components to improve accuracy. Examples: Analog ICs: amplifiers, ADCs, voltage regulators, references, clocks Passives: Resistors, shunts, capacitors, diodes Other sensors: pressure, flow, inductive, capacitive, thermocouples Optics & Displays: LEDs, Photodiodes, LDC Key Terms: offset drift, gain drift, temperature coefficient, Uncompensated 0C 25C 60C Pressure (psi) 5

6 Commonly Used Temperature Sensors Temp Sense IC Thermistor RTD Thermocouple Temp Range -55 C to +150 C -100 C to +500 C -240 C to 600 C -260 C to C Accuracy Good / Best Depends on Calibration Best Good Linearity Best Low Best Better Circuitry & Software Complexity Easy Moderate Complex Complex Topology Point to Point Multi-Drop Daisy Chain Point to Point Point to Point Point to Point Price Low-Moderate Low-Moderate Expensive Expensive

7 Resistance [Ω] NTC Thermistor Thermistors are passive components that change resistance with temperature. Thermistors fall into two categories, NTC (negative temperature coefficient) and PTC (positive coefficient) Thermistor Vcc RT Amp ADC Typical Implementation Pros: Relatively low cost: $0.01 to $0.15 Easy to source: Cons: Non-linearity Software overhead: Memory or MIPS Long term reliability # of components Difficult to determine actual system accuracy Thermistor Nominal Resistance NTC Temperature [C] 7

8 Output Voltage [V] NTC System Error Example Circuit: 10K NTC (1%, 1% Beta) + 10K Rbias. (1%, 100ppm/C) Contributors: NTC (Tolerance, Beta) Bias Resistor (Tolerance, Temperature Drift) Reference voltage ADC (quantization error) Linearization Error Divider Output Voltage NTC Vout Nom Temperature [C] 8

9 RTD (Resistive Temperature Detectors) Temperature sensor consisting of a pure material typically platinum, nickel, or copper with a predictable resistance / temperature relationship. Common naming: PT100: Platinum o C PT1000: Platinum o C Pros: Platinum RTDs can be extremely accurate and predictable over temperature Very linear Wide temperature range up to 600 o C Cons: Change in resistance over temperature is small Complex system design requiring precision matched traces, kelvin connections, and/or chopping circuits High cost of components Platinum RTDs are expensive, other materials used are less accurate Precision bias & reference resistor network, current reference, amplifier, ADC Complex error analysis due to the high number of contributing components. (RTD, resistors, amp, ADC, current source) Annual calibration 9

10 RTD System Error Contributors: RTD tolerance (see table) Non-linearity (Callendar-Van Dusen) For t > 0 C: Rt = R0 (1 + At + Bt²) For t < 0 C: Rt = R0 (1 + At + Bt² + C (t - 100) t³) Self-heating ADC offset / gain tolerance & temperature drift References 10

11 Thermocouples A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric Seebeck effect. This voltage translates to the difference in temperature between the hot junction (T h ) and the cold junction (T c ). Type J Iron Isothermal Block Copper + Pros: No external excitation -> No self heating Extreme temperatures: >2000 o C. Inexpensive Rugged Lower cost than RTDs T h Constantan T c TMP Copper - Cons: Additional temperature sensor needed for cold junction compensation (CJC) Non-linear Sensitive to parasitic junctions where thermocouple attached to board Cold Junction Compensation Temperature Sensor

12 Silicon Temperature Sensors Silicon temperature sensors rely on the predictive temperature dependence of a silicon bandgap. The TI Advantage I V be >45 Years of experience Best in class accuracy, size, and power Largest portfolio Industry s leading obsolescence policy Pros: Highly linear Guaranteed accuracy across wide temperature range (up to +/-0.1 o C) Available with a wide range of integration Examples: ADC, Comparator,, Humidity sensor, Current Amplifier Comparably priced to similar accuracy technologies Low power (down to 4.2uW) Significant power savings Cons: Limited temperature range (-55 o C to 150 o C) Few packaging options for measuring off PCB than thermistors IC Temp sensor

13 IC Temperature Sensors Solutions On Board Temperature Solutions V Analog T Local Measures temp at device itself 35 o C Digital I2C SPI Pulse Count UART Remote Multi-channel, Measures temp at external PN junction 35 o C 65 o 40 C o 55 C o C Switch/Thermostat Simple Over Temperature Protection Hot Cold Alert Off Board Temperature Solutions 2 Pin (Point to Point) Can be integrated into probes Up to 2 meters Daisy Chain String multiple sensors in a single cable Up to 300 meters Humidity Integrated Humidity & Temperature Sensors

14 Single Chip Over Temperature Protection Temp Switch (Thermostat) Automatically detects over temperature condition and issues Alert Compact Single Chip Solutions Guaranteed Accuracy to maximize charging without sacrificing safety. No calibration No sensitivity to humidity Optional Features: Programmable Hysteresis Analog Temperature Output Dual Threshold Alerts Window Comparator Alert. Alert 50 o C 60 o C T (TRIP) Replaces Thermistor + Comparator Vcc Thermistor RT + Comp - GPIO Vref

15 Temperature Switches Q100 Option Available Factory Programmed Pin Programmable Multiple Programming Options Available Resistor Programmable Resistor Programmable W/ Analog Temp Vcc Hyst 0 Hyst 1 TMP303 Alert Vcc GPIO TMP302 Tripset 0 Tripset 1 Hystset Alert Vcc GPIO TMP708 Tripset 0 Hyst Alert Vcc GPIO Tripset 0 Hyst LM57 Alert Vout GPIO ADC TMP303 +/- 1C Accuracy Selectable Hysteresis: 1/2/5/10 C Window Comparator 1.4V to 3.6V SOT-563 Package 1.6 x 1.6mm Footprint LM57 TMP302A/B/C/D TMP708/TMP709 +/- 1.5C Accuracy -40 C to 150 C +/- 2C Accuracy +/- 3.5C Accuracy Select Hysteresis: Selectable Trip Point: 50 C, 55 C, 60 C, 65 C Selectable Hysteresis: 2.4V to 5.5V 70 C,75 C, 80 C, 85 C 2 C / 10 C / 30 C WSON & TSSOP 90 C, 95 C, 100 C, 105 C 2.7V to 5.5V 110 C, 115 C, 120 C, 125 C SOT-23 TMP300 Open Drain Local = 6 C Max Accuracy Selectable Hysteresis: 1.8V to 18V LM56 Dual Trip Point +/- 2C Accuracy -40 C to 150 C Select Hysteresis: 5 C / 10 C 2.7V to 10V SOIC & VSSOP

16 Upgrading from Thermistors to ICs Thermistor Vcc Thermistor Configuration RT ADC Analog Temp IC Temp IC Out ADC Digital Temp IC Alert Temp IC SDA Addr SCL Vcc SPI/I2C Active Temperature Monitoring Digital Temp: High Integration & Programmability TMP1075: Upgrade to LM75, TMP75 TMP112: Compact, 0.5C accuracy TMP103: Ultra-compact 0.8 x 0.8mm Analog Temp High Linearity, Low power TMP235: Best accuracy for price LMT70: 0.13C accuracy Thermistor 1 Vcc RT Amp Thermistor n Vcc RT Thermistor Configuration Amp 1 2 n Mux ADC Mux may be internal to Remote Temp IC Alert Temp IC SDA SCL Vcc SPI/I2C Multi-Point Active Temp Monitoring Remote Diode: measure any PN junction TMP468: 8+1 channel TMP464: 4+1 channel TMP461: High accuracy single channel Other topologies: TMP107: Daisy Chain Configuration LMT01: 2 wire pulse count

17 Cable / Probe Topology Options Point to Point Daisy-Chain Device: LMT01 Interface: Digital Pulse Counter Requirements: GPIO & Counter Distance: Up to 2 Meters Maximum Nodes: Unlimited Accuracy: +/-0.5 o C max Key Advantages: 2 Wires Only Mechanically compatible with thermistor, RTD, thermocouple probes. Zero Calibration Device: TMP107 Interface: SMAART Wire Requirements: ½ Duplex UART Distance: Up to 300 Meters Maximum Nodes: 32** Accuracy: +/-0.4 o C max Key Advantages: Auto Addressing and programmable Alerts Non-Volatile Memory Reduces overall cabling Reduces assembly time Zero Calibration 17 **Contact TI for higher node count

18 LMT01: Digital Pulse Counter Interface Current is modulated between 34uA and 125uA to create a series of pulses 1 Pulse = 1 LSB Temp = # of pulse x I out GPIO 1 Up to 2m LMT01 GPIO 2 / Comparator 125uA I out 34uA 18

19 TMP107: SMAART Wire Interface ½ Duplex UART interface Auto addressing based upon location in the chain Non-volatile memory is available to store address & programming TX V TMP107 I/01 LOGIC I/02 V TMP107 I/01 LOGIC I/02 V TMP107 I/01 LOGIC I/02 V TMP107 I/01 LOGIC I/02 RX EEPROM GND EEPROM GND EEPROM GND EEPROM GND Bus Host 12 nd Times out and chain is back to forward buffer This Device process sends Acknowledges initialization continues until address the the host. last to Increments the device First Acknowledges Device the address in Chain. the and Device Host. passes stores along, this which Address is stored in EEPROM by 23 nd rd Device All the devices know their position in the bus for any further reads and writes

20 Error ( o C) Ultra-high Accuracy: RTD Performance 3-Wire RTD VS TMP117: I2C Temp Sensor TMP117: Integrated sensor, ADC, and EEPROM 16-Bit resolution ( o C) Low power: 1sps 250nA shutdown 1.8V to 5.5V I2C interface with programmable Alert Operating range -60 o C to 150 o C NIST Traceable Film Platinum RTD vs TMP117 *Does not include RTD system error Class B Class A Class AA TMP117 Temperature ( o C) 20

21 TI Temp Sensors: High accuracy portfolio LMT70 TMP117 TMP116 TMP112 TMP275 Interface Analog I2C w/ Alert + EEPROM I2C w/ Alert Supply Range 2.5V to 5.5V 1.8V to 5.5V 1.9V to 5.5V 1.4V o 3.6V 2.5V to 5.5V I2C Addresses Available N/A 4 8 Accuracy (max) 0.13 C 0.20 C 0.36 C (20 C to 42 C) (-20 C to 90 C) (-55 C to 150 C) 0.1 C (-10 C to 50 C) 0.20 C (-40 C to 125 C) 0.3 C (-55 C to 150 C) 0.2 C (-10 C to 85 C) 0.25 C (-40 C to 105 C) 0.3 C (-105 C to 125 C) 0.5 C ( 0 C to 65 C ) 1.0 C (-40 C to 125 C) 0.5 C ( -20 C to 100 C ) 1.0 C (-40 C to 125 C) Resolution mv/ C 16-Bit 12-Bit Quiescent Current (max) 12uA 4.5uA 10 ua 85uA Shutdown Current 50nA 500nA 1 ua 3mA Package Footprint WCSP 0.8x0.8mm WSON (2.0mm x 2.0mm) WCSP (1.0mm x 1.6mm) WSON 2.0mm x 2.0mm SOT x 1.6mm SO-8 (3.0mm x 4.9mm) MSOP-8 (4.9mm x 6.0mm)

22 Temp Sensors: Integrated Features Humidity Integrated Humidity & Temp HDC2010: Ultra-small BGA package HDC2080 QFN package Current Shunt Monitor Integrated Digital Current / Voltage / Power Monitor TMP512: 2 Remote Ch + Local TMP513: 3 Remote Ch + Local Fan Control & System Monitoring Integrated Fan Control & System Monitoring AMC80: Temp + 2x Tach + 7x ADC LM87: Remote Temp + 2x Fan, DAC LM96164: 4x Remote + 4x Tach + 2 PWM + 9x ADC % Fan DAC / PWM PI Tach Lookup ADC Vcc Monitors Intrusion Detection 22