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Introduction this Handbook Temperature Sensing Techniques. RTDs Thermistors Thermocouples. Silicon Temperature Sensors
National's Temperature Sensor Voltage-Output Analog Temperature Sensors LM135, LM235, LM335 Kelvin Sensors. LM35, LM45 Celsius Sensors LM34 Fahrenheit Sensor LM50 "Single Supply" Celsius Sensor LM60 2.7V Single Supply Celsius Sensor Current-Output Analog Sensors LM134, LM234, LM334 Current-Output Temperature Sensors Comparator-Output Temperature Sensors LM56 Low-Power Thermostat Digital Output Sensors LM75 Digital Temperature Sensor Thermal Watchdog With Two-Wire Interface LM78 System Monitor Application Hints. Sensor Location Accurate Measurements. Example Audio Power Amplifier Example Personal Computer Example Measuring Temperature Mapping Temperature Output Voltage Current Driving Capacitive Loads (These hints apply analog-output sensors) Noise Filtering
Application Circuits Personal Computers Simple Controller Low/High Controllers Digital Temperature Monitor Interfacing External Temperature Sensors LM75-to-PC interface Isolated LM75-to-PC Low-Power Systems Low-Voltage, Low-Power Temperature Sensor with "Shutdown" Battery Management Power" Battery Temperature Monitors
Audio Power Amplifier Heat Sink Temperature Detector Controller Other Applications Two-Wire Temperature Sensor 4-to-20mA Current Transmitter (0°C 100°C) Multi-Channel Temperature-to-Digital Converter Oven Temperature Controllers Isolated Temperature-to-Frequency Converter
Audio
Datasheets. LM34 LM35 LM46 LM50 LM56 LM60 LM75 LM77 LM78 LM80 LM134 LM135
Introduction This Handbook
Temperature most often-measured environmental quantity. This might expected since most physical, electronic, chemical, mechanical biological systems affected temperature. Some processes work well only within narrow range temperatures; certain chemical reactions, biological processes, even electronic circuits perform best within limited temperature ranges. When these processes need optimized, control systems that keep temperature within specified limits often used. Temperature sensors provide inputs those control systems. Many electronic components damaged exposure high temperatures, some damaged exposure temperatures. Semiconductor devices LCDs (Liquid Crystal Displays) examples commonly-used components that damage temperature extremes. When temperature limits exceeded, action must taken protect system. these systems, temperature sensing helps enhance reliability. example such system personal computer. computer's motherboard hard disk drive generate great deal heat. internal helps cool system, fails, airflow blocked, system components could permanently damaged. sensing temperature inside computer's case, hightemperature conditions detected actions taken reduce system temperature, even shut system down avert catastrophe. Other applications simply require temperature data that temperatures effect process accounted for. Examples battery chargers (batteries' charge capacities vary with temperature cell temperature help determine optimum point which terminate fast charging), crystal oscillators (oscillation frequency varies with temperature) LCDs (contrast temperature-dependent compensated temperature known). This handbook provides introduction temperature sensing, with focus silicon-based sensors. Included several example application circuits, reprints magazine articles temperature sensing, selection guide help choose silicon-based sensor that appropriate your application.
Temperature Sensing Techniques
Several temperature sensing techniques currently widespread usage. most common these RTDs, thermocouples, thermistors, sensor ICs. right your application depends required temperature range, linearity, accuracy, cost, features, ease designing necessary support circuitry. this section discuss characteristics most common temperature sensing techniques. RTDs Resistive sensors sensing element whose resistance varies with temperature. platinum (Resistance Temperature Detector) consists coil platinum wire wound around bobbin, film platinum deposited substrate. either case, sensors resistance-temperature curve nearly-linear function, shown Figure 2.1. RTDs resistance curve lower one; straight line also shown reference. Nonlinearity several degrees temperature extremes, highly predictable repeatable. Correction this nonlinearity done with linearizing circuit digitizing measured resistance value using lookup table apply correction factors. Because curve's high degree repeatability over wide temperature range (roughly -250 degrees +750 degrees platinums stability (even when hot), you'll find RTDs variety precision sensing applications.
Resistance Temperature
Resistance -200
Temperature
Figure 2.1. Resistance Temperature. upper curve straight line reference.
Temperature Sensor Handbook
Complexity signal processing circuitry varies substantially depending application. Usually, known, accurate current forced through sensor, voltage across sensor measured. Several components, each which generates errors, necessary. When leads sensor long, four-wire connections sensor eliminate effects lead resistance, this increase amplifier's complexity. Low-voltage operation possible with resistive sensors there inherent minimum voltage limitations these devices there enough precision low-voltage amplifiers available make voltage operation reasonable achieve. Low-power operation little tougher, done expense complexity using intermittent power techniques. energizing sensor only when measurement needs made, power consumption minimized. RTDs have drawbacks some applications. example, cost wire-wound platinum tends relatively high. other hand, thin-film RTDs sensors made from other metals cost little dollars. Also, self-heating occur these devices. power required energize sensor raises temperature, which affects measurement accuracy. Circuits that drive sensor with current develop self-heating errors several degrees. nonlinearity resistance-vs.-temperature curve disadvantage some applications, mentioned above, very predictable therefore correctable. Thermistors Another type resistive sensor thermistor. Low-cost thermistors often perform simple measurement trip-point detection functions low-cost systems. Low-precision thermistors very inexpensive; higher price points, they selected better precision single temperature. thermistors resistance-temperature function very nonlinear (Figure 2.2), want measure wide range temperatures, you'll find necessary perform substantial linearization. alternative purchase linearized devices, which generally consist array thermistors with some fixed resistors. These much more expensive less sensitive than single thermistors, their accuracy excellent. Simple thermistor-based set-point thermostat controller applications implemented with very components just thermistor, comparator, resistors will job.
Thermistor Resistance Temperature 100k
Resistance
Temperature
Thermistor Resistance Temperature 100k -100
Resistance
Temperature (oC)
Figure 2.2. Thermistor Resistance Temperature. linear scale. logarithmic scale.
Temperature Sensor Handbook
When functionality requirements more involved (for example multiple trip points analog-to-digital conversion necessary), external circuitry cost increase quickly. Consequently, you'll typically lowcost thermistors only applications with minimal functionality requirements. Thermistors affected self-heating, usually higher temperatures where their resistances lower. with RTDs, there fundamental reasons thermistors shouldn't used supply voltages. External active components such comparators amplifiers will usually limit supply voltage range. find thermistors that will work over temperature range from about -100°C +550°C although most rated maximum operating temperatures from 100°C 150°C. Thermocouples thermocouple consists junction wires made different materials. example, Type thermocouple made from iron constantan wires, shown Figure 2.3. Junction temperature measured. Junctions kept different, known temperature. output voltage approximately proportional difference temperature between Junction Junctions Typically, you'll measure temperature Junctions with second sensor, shown figure. This second sensor enables develop output voltage proportional appropriate scale (for example, degrees adding voltage thermocouple output that same slope that thermocouple, related temperature junctions
Copper Iron Thermocouple Measurement Junction 100k LM35 10mV/oC
Cold-junction compensated output. 50.2 V/oC
Constantan
Copper
Figure 2.3.
Because thermocouples "sensitivity" reflected Seebeck coefficient) rather small order tens microvolts degree need low-offset amplifier produce usable output voltage. Nonlinearities temperature-to-voltage transfer function (shown Figure 2.4) amount many degrees over thermocouples operating range and, with RTDs thermocouples, often necessitate compensation circuits lookup tables. spite these drawbacks, however, thermocouples very popular, part because their thermal mass wide operating temperature range, which extend about 1700°C with common types. Table shows Seebeck coefficients temperature ranges thermocouple types.
Temperature Sensor Handbook
Type Thermocouple Output Voltage Temperature Vout (mV) -200 -100 Temperature (°C)
Type Thermocouple Deviation From Straight Line Error (°C) -200 -100
Temperature (°C)
Figure 2.4. Output voltage function temperature Type thermocouple. Approximate error straight line that passes through curve 750°C
Table 2.1. Seebeck Coefficients Temperature Ranges various thermocouple types. Type Seebeck Coefficient µV/°C 58.5@0°C 50.2@0°C 39.4@0°C 11.5@0°C Temperature Range (°C) 1700 -200 1250 1450
Silicon Temperature Sensors Integrated circuit temperature sensors differ significantly from other types couple important ways. first operating temperature range. temperature sensor operate over nominal temperature range -55°C +150°C. Some devices beyond this range, while others, because package cost constraints, operate over narrower range. second major difference functionality. silicon temperature sensor integrated circuit, therefore include extensive signal processing circuitry within same package sensor. don't need design cold-junction compensation linearization circuits temperature sensor ICs, unless have extremely specialized system requirements, there need design comparator circuits convert their analog outputs logic levels digital codes. Those functions already built into several commercial ICs.
Temperature Sensor Handbook
National's Temperature Sensor
National builds wide variety temperature sensor that intended simplify broadest possible range temperature sensing challenges. Some these analog circuits, with either voltage current output. Others combine analog sensing circuits with voltage comparators provide "thermostat" "alarm" functions. Still other sensor combine analog sensing circuitry with digital control registers, making them ideal solution microprocessor-based systems such personal computers. Below summary National's sensor products August, 1996. Unless otherwise noted, specifications listed this section guaranteed limits best grade device.
Voltage-Output Analog Temperature Sensors
LM135, LM235, LM335 Kelvin Sensors LM135, LM235, LM335 develop output voltage proportional absolute temperature with nominal temperature coefficient 10mV/K. nominal output voltage therefore 2.73V 0°C, 3.73V 100°C. sensors this family operate like 2-terminal shunt voltage references, nominally connected shown Figure 3.1. third terminal allows adjust accuracy using trimpot shown Figure. error untrimmed LM135A over full -55°C +150°C range less than ±2.7°C. Using external trimpot adjust accuracy reduces error less than ±1°C over same temperature range. sensors this family available plastic TO-92 SO-8 packages, TO-46 metal can.
OUTPUT 10mV/°K
LM335
Figure 3.1. Typical Connection LM135, LM235, LM335. Adjust potentiometer correct output voltage known temperature (for example 2.982V 25°C), obtain better than ±1°C accuracy over -55°C +150°C temperature range.
LM35, LM45 Celsius Sensors LM35 LM45 three-terminal devices that produce output voltages proportional (10mV/°C), nominal output voltage 250mV 25°C 1.000V 100°C. These sensors measure temperatures below using pull-down resistor from output voltage below "ground" (see "Applications Hints" section). LM35 more accurate (±1°C from -55°C +150°C ±3°C from -20°C +100°C), while LM45 available "Tiny" SOT-23 package. LM35 available plastic TO-92 SO-8 packages, TO-46 metal can.
(+5V +20V) (+5V +20V) (+4V +10V)
LM34
OUTPUT VOUT +10mV/°F
LM35
OUTPUT VOUT +10mV/°C
LM45
OUTPUT VOUT +10mV/°C
Figure 3.2. LM34, LM35, LM45 Typical Connections. Each essentially 3-terminal device (supply, ground, output), although some available packages with more pins.
Temperature Sensor Handbook
LM34 Fahrenheit Sensor LM34 similar LM35, output voltage proportional (10mV/°F). accuracy similar LM35 (±2°F from -50°F +300°F), available same TO-92, SO-8, TO-46 packages LM35. LM50 "Single Supply" Celsius Sensor LM50 called "Single Supply" Celsius Sensor because, unlike LM35 LM45, measure negative temperatures without taking output below ground (see "Applications Hints" section). This simplify external circuitry some applications. LM50's output voltage 10mV/°C slope, 500mV "offset". Thus, output voltage 500mV 0°C, 100mV -40°C, 1.5V +100°C. Accuracy within over full -40°C +125°C operating temperature range. LM50 available SOT-23 package.
(4.5V 10V)
LM50
OUTPUT VOUT 10mV/°C 500mV
Figure 3.3. LM50 Typical Connection
LM60 2.7V Single Supply Celsius Sensor LM60 similar LM50, intended applications with supply voltages 2.7V. 110µA supply current drain enough make LM60 ideal sensor battery-powered systems. LM60's output voltage 6.25mV/°C slope, 424mV "offset". This results output voltages 424mV 0°C, 174mV -40°C, 1.049V 100°C. LM60 available SOT-23 package.
(2.7V 10V)
LM60
OUTPUT VOUT 6.25mV/°C 424mV
Figure 3.4. LM60 Typical Connection
Current-Output Analog Sensors
LM134, LM234, LM334 Current-Output Temperature Sensors Although data sheet calls "adjustable current source", LM134 also current-output temperature sensor with output current proportional absolute temperature. sensitivity using single external resistor. Typical sensitivities 1µA/°C 3µA/°C range, with 1µA/°C being good nominal value. adjusting value external resistor, sensitivity trimmed good accuracy over full operating temperature range (-55°C +125°C LM134, -25°C +100°C LM234, +70°C LM334). LM134 typically needs only 1.2V supply voltage, useful applications with very limited voltage headroom. Devices this family available SO-8 TO-92 plastic packages TO-46 metal cans.
Temperature Sensor Handbook
LM134
RSET
V227 V/oK RSET
ISET
VOUT (ISET)(RL) =10mV/oK RSET
Figure 3.5. LM134 Typical Connection. RSET controls ratio output current temperature.
Comparator-Output Temperature Sensors
LM56 Low-Power Thermostat LM56 includes temperature sensor (similar LM60), 1.25V voltage reference, comparators with preset hysteresis. will operate from power supply voltages between 2.7V 10V, draws maximum 200µA from power supply. operating temperature range -40°C +125°C. Comparator trip point tolerance, including sensor, reference, comparator errors (but including external resistor errors) from 25°C 85°C, from -40°C +125°C. internal temperature sensor develops output voltage 6.2mV T(°C) 395mV. Three external resistors thresholds comparators.
Temperature Sensor Handbook
THYST VTEMP
THYST
OUT2
OUT1
Figure 3.6. LM56 block diagram. Comparator outputs function temperature.
Digital Output Sensors
LM75 Digital Temperature Sensor Thermal Watchdog With Two-Wire Interface LM75 contains temperature sensor, delta-sigma analog-to-digital converter (ADC), two-wire digital interface, registers controlling IC's operation. two-wire interface follows I2C® protocol. Temperature continuously being measured, read time. desired, host processor instruct LM75 monitor temperature take output high (the sign programmable) temperature exceeds programmed limit. second, lower threshold temperature also programmed, host notified when temperature dropped below this threshold. Thus, LM75 heart temperature monitoring control subsystem microprocessor-based systems such personal computers. Temperature data represented 9-bit word sign magnitude bits), resulting 0.5°C resolution. Accuracy ±2°C from -25°C +100°C ±3°C from -55°C +125°C. LM75 available 8-pin package.
registered trademark Philips Corporation.
Temperature Sensor Handbook
Temperature Sensor
9-Bit Delta-Sigma
Limit Comparison O.S.
LM75
Control Logic
Hysteresis Register
Over-Temp Shutdown Register
INTERFACE
Figure 3.7. LM75 Block Diagram.
LM78 System Monitor LM78 highly-integrated Data Acquisition system that monitor several kinds analog inputs simultaneously, including temperature, frequency, analog voltage. ideal single-chip solution improving reliability servers, Personal Computers, virtually microprocessor-based instrument system. includes temperature sensor, interfaces, multiple-input 8-bit (five positive inputs negative inputs), speed counters, several control memory registers, numerous other functions. LM78 used monitor power supply voltages, temperatures, speeds. values these analog quantities continuously digitized read time. Programmable WATCHDOGlimits these analog quantities activate fully-programmable maskable interrupt system with outputs. input provided overtemperature outputs additional temperature sensors (such LM56 LM75) this linked interrupt system. Additional inputs provided Chassis Intrusion detection circuits, monitor inputs, chainable interrupt. 32-byte auto-increment provided POST (Power Self Test) code storage. LM78 operates from single power supply draws less than supply current while operating. shutdown mode, supply current drops 10µA.
Temperature Sensor Handbook
Positive Analog Inputs Negative Analog Inputs 8-Bit
power supply voltages, analog temperature sensors, other voltages monitored.
Interrupt Outputs Limit Registers WATCHDOG Comparators Interrupt Masking Interrupt Control
Chassis Intrusion Detector
Chassis Intrusion +12V Inputs
Temperature Sensor
Speed Counter
Interface Control
LM78
Interface
LM75 Digital O.S. Temperature Sensor
LM75 Digital O.S. Temperature Sensor
Figure 3.8. LM78 highly-integrated system monitoring circuit that tracks only temperature, also power supply voltages, speed, other analog quantities.
Application Hints
following Application Hints apply most National's temperature sensor ICs. hints that specific particular sensor, please refer that sensors data sheet. Sensor Location Accurate Measurements temperature sensor produces output, whether analog digital, that depends temperature sensor. Heat conducted sensing element through sensors package metal leads. general, sensor metal package (such LM35 TO46) will have dominant thermal path through package. sensors plastic packages like TO-92, SO-8, SOT-23, leads provide dominant thermal path. Therefore, board-mounted sensor will fine measuring temperature circuit board (especially traces which leads soldered). board's temperature very close ambient temperature (that board significant heat generators mounted it), sensors temperature will also very near that ambient air. want measure temperature something other than circuit board, must ensure that sensor leads same temperature object wish measure. This usually involves making good mechanical thermal contact example, attaching sensor (and leads) object being measured with thermally-conductive epoxy. electrical connections made directly from sensors leads object being measured, soldering leads sensor object will give good thermal connection. ambient temperature same that surface being measured, sensor will within fraction degree surface temperature. temperature much higher lower
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Temperature Sensor Handbook
than surface temperature, temperature sensor will inter-mediate temperature between surface temperature temperature. sensor plastic package TO-92 SOT-23, example) will indicate temperature very close that leads (which will very close circuit board's temperature), with temperature having less significant effect. sensor metal package (like TO-46) will usually influenced more temperature. influence temperature further increased gluing clamping heat sink metal package. liquid temperature measured, sensor mounted inside sealed-end metal tube, then dipped into bath screwed into threaded hole tank. Temperature sensors accompanying wiring circuits must kept insulated dry, avoid leakage corrosion. This especially true temperature sensors circuit operate cold temperatures where condensation occur. Printed-circuit coatings varnishes such Humiseal epoxy paints dips often used ensure that moisture cannot corrode sensor connections. where should sensor your application? Here three examples: Example Audio Power Amplifier often desirable measure temperature audio power amplifier protect electronics from overheating, either activating cooling shutting system down. Even amplifier that contains internal circuitry shut amplifier down event overheating (National's OvertureTM-series amplifiers, example) benefit from additional temperature sensing. activating cooling when temperature gets high, system produce more output power longer periods time, still avoids having (and producing noise) when output levels low. Audio amplifiers that dissipate more than watts virtually always have their power devices (either discrete transistors entire monolithic amplifier) bolted heat sink. heat sinks temperature depends ambient temperature, power device's case temperature, power device's power dissipation, thermal resistance from case heat sink. Similarly, power device's case temperature depends device's power dissipation thermal resistance from silicon case. heat sinks temperature therefore equal "junction temperature", dependent related practical monitor power device's temperature mount sensor heat sink. sensors temperature will lower than that power device's die, understand correlation between heat sink temperature temperature, sensors output will still useful. Figure shows example monolithic power amplifier bolted heat sink. Next amplifier temperature sensor TO-46 metal package. sensor package hole drilled into heat sink; sensor cemented heat sink with heat-conducting epoxy. Heat conducted from heat sink through sensors case, from circuit board through sensors leads. Depending amplifier, heat sink, printed circuit board layout, sensor, best indication amplifier's temperature obtained through metal package through sensors leads. amplifier IC's leads will normally within degrees temperature heat sink near amplifier. amplifier soldered directly printed circuit board, leads short, circuit board traces amplifier's leads will quite close heat sink temperature sometimes higher, sometimes lower, depending thermal characteristics system. Therefore, sensor soldered point very close amplifier's leads, you'll good correlation with heat sink temperature. This especially good news you're using temperature sensor plastic package, since thermal conduction such device through leads. Locate sensor close possible amplifier's leads. amplifier ground pin, place sensors ground right next that amplifier keep other sensor leads same temperature amplifier's leads. heat sink mounted back side printed circuit board, sensor mounted board, close practical power device(s). This will provide good correlation between measured temperature heat sink temperature.
Temperature Sensor Handbook
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Figure 4.1. TO-220 power amplifier TO-46 sensor mounted heat sink. Excellent results also obtained locating sensor circuit board very close amplifier IC's leads.
Example Personal Computer High-performance microprocessors such Pentium® Power families consume power enough suffer catastrophic damage excessive temperature. enhance system reliability, often desirable monitor processor temperature activate cooling fan, slow down system clock, shut system down completely processor gets hot. with power amplifiers, there several potential mounting sites sensor. such location center hole drilled into microprocessors heat sink, shown location Figure 4.2. heat sink, which clipped processor attached with epoxy, generally sits processor. advantage this location that sensors temperature will within degrees microprocessors case temperature typical assembly. disadvantage that relatively long leads will required return processor's output circuit board. Another disadvantage that heat-sink-to-microprocessor thermal connection degrades (either because epoxy because clip-on heat sink gets "bumped" longer intimate contact with processor), sensor-to-microprocessor connection will probably also disrupted, which means that sensor will lower than normal temperature while processor temperature rising potentially damaging level. Another potential location cavity beneath socketed processor (Figure 4.2, location "b"). advantage this site that, since sensor attached circuit board using conventional surface-mounting techniques, assembly straightforward. Another advantage that sensor isolated from flow will influenced excessively changes ambient temperature, speed, direction cooling flow. Also, heat sink becomes detached from microprocessor, sensor will indicate increase microprocessor temperature. disadvantage that thermal contact between sensor processor good previous example, which result temperature differences between sensor microprocessor case 10°C. This only minor disadvantage, however, this approach most practical many systems. also possible mount sensor circuit board next microprocessors socket (location "c"). This another technique that compatible with large-volume manufacturing, correlation between sensor temperature processor temperature much weaker (the microprocessor case much 20°C warmer than sensor).
Pentium registered trademark Intel Corporation. Power registered trademark Corporation.
Hole drilled heatsink Pentium Similar Processor
Socket
Figure 4.2. Three potential sensor locations high-performance processor monitoring.
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Temperature Sensor Handbook
Finally, some lower-cost systems microprocessor soldered motherboard, with heat sink mounted opposite side motherboard, shown Figure 4.3. these systems, sensor soldered board edge heat sink. Since microprocessor close contact with motherboard, sensors temperature will closer that microprocessor than socketed microprocessor.
Pentium Similar Processor Ground Plane Feedthroughs
Temperature Sensor
Figure 4.3. Sensor mounted near edge soldered processor.
Example Measuring Temperature Because sensors leads often dominant thermal path, board-mounted sensor will usually excellent measuring board temperature. what want measure temperature? board same temperature air, you're luck. board different temperatures, things more complicated. sensor isolated from board using long leads. sensor metal can, clip-on heat sink bring sensors temperature close ambient. sensor plastic package, need mounted small "subboard", which then thermally isolated from main board with long leads. more information finding ideal location temperature sensor, refer article "Get Maximum Accuracy From Temperature Sensors" Jerry Steele (Electronic Design, August 1996). Mapping Temperature Output Voltage Current earliest analog-output temperature sensors developed National generated output signals that were proportional absolute temperature (K). LM135 series nominal output voltage equal 10mV/K, while LM134 series current-output device) produces current proportional absolute temperature. scaling factor determined external resistor. Because Celsius Fahrenheit scales more convenient many applications, three sensors have output voltages proportional those scales. LM35 LM45 produce nominal output voltages equal 10mV/°C, while LM34 produces nominal output equal 10mV/°F. While Celsius Fahrenheit sensors have more convenient temperature-to-voltage mapping than absolute temperature sensors, they somewhat less convenient when need look temperatures below 0°F. measure "negative" temperatures with these devices, need either provide negative power supply Figure 4.4(a), bias sensor above ground look voltage differential between output "ground" pins Figure 4.4(b).
10V) Choose -V-/50µA VOUT 10mV/°C 1.00V 100°C 250mV 25°C VOUT -200mV -20°C 10V)
LM45
LM45
VOUT
VOUT
Figure 4.4. ways measure negative temperatures with single-supply sensors. negative supply voltage available, pulldown resistor allow sensors output below ground. Alternatively, bias "ground" using diode, voltage reference, other voltage source. differential output voltage will negative negative temperatures.
Temperature Sensor Handbook
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LM50 LM60 alternative approach. These devices have built-in positive offset voltage that allows them produce output voltages corresponding negative temperatures when operating single positive supply. LM50 10mV/°C scale factor, output voltage 500mV 0°C. device specified temperatures -40°C (100mV). LM60's scale factor 6.25mV/°C, output voltage 424mV 0°C. LM60 also specified temperatures -40°C (174mV). Driving Capacitive Loads (These hints apply analog-output sensors). National's temperature sensor micropower circuits, like most micropower circuits, they generally have limited ability drive heavy capacitive loads. LM34 LM35, example, drive 50pF without special precautions, while LM45 handle 500pF. heavier capacitive loads anticipated, easy isolate decouple load with resistor; Figure 4.5. Note that series resistor will attenuate output signal unless load resistance very high. this problem, improve tolerance capacitive loading without increasing output resistance using series damper from output ground shown Figure 4.5.
HIGH-RESISTANCE LOAD HEAVY CAPACITIVE LOAD (CABLE, ETC.)
LM34, LM35, LM45
HEAVY CAPACITIVE LOAD (CABLE, ETC.)
LM34, LM35, LM45
LOAD
Figure 4.5. Capacitive drive options. LM34, LM35, LM45 drive large external capacitance isolated from load capacitance with resistor (a), compensated with network (b).
LM50 LM60 have internal isolation resistances drive value capacitance with stability problems. Ensure that load impedance sufficiently high avoid attenuation output signal, Noise Filtering linear circuit connected wires hostile environment have performance adversely affected intense electromagnetic sources such relays, radio transmitters, motors with arcing brushes, transients, etc., wiring receiving antenna internal junctions rectifiers. such cases, 0.1µF bypass capacitor from power supply ground will help clean power supply noise. Output filtering added well. Sensors like LM50 LM60 drive filter capacitors directly; 4.7µF output capacitor generally works well. When using sensors that should directly drive large capacitive loads, isolate filter capacitor with resistor shown Figure 4.5(a), damper Figure 4.5(b) provide filtering. Typical damper component values series with 0.2µF 1µF.
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Temperature Sensor Handbook
Application Circuits Personal Computers
Recent generations personal computers dissipate power, which means they tend hot. microprocessor hard disk drive notable spots. Cooling fans help keep heat under control, fails, ventilation paths become blocked dust desk clutter, temperature inside computer's case high enough dramatically reduce life internal components. Notebook computers, which have cooling fans, even more difficult. High-performance personal computers servers monolithic temperature sensors their motherboards monitor system temperatures avert system failure. Typical locations sensors near (sometimes under) microprocessor, inside hard disk drive. notebook computer, when sensor detects excessive temperature, system reduce clock frequency minimize power dissipation. Fast temperature rise inside desktop unit server indicate failure well-designed system notify user that unit needs servicing. temperature continues rise, system shut itself off. Simple Controller circuit Figure senses system temperature turns cooling when sensors temperature exceeds preselected value. LM56 thermostat senses temperature compares sensor output voltage voltages pins, which using three external resistors. 1.25V system voltage reference internal. shown, will will turn when sensors temperature exceeds 50°C. sensors temperature rises above 70°C, will low. This output used slow system clock reduce processor power) drive interrupt that causes microprocessor initiate shutdown procedure. second output isn't needed, replace 9.09k resistor with short, replace 2.67k resistor with 11.8k resistor. will still T=50°C, will remain inactive. Typically, LM56 will located circuit board close possible microprocessor that temperature will near that processor. This circuit designed fan. alternative approach with p-channel MOSFET shown Figure
Figure 5.1. This circuit turns cooling when LM56's temperature exceeds 50°C. OUT2 goes when temperature reaches 70°C. comparator outputs open collector, OUT2 will need pull-up resistor drive logic input.
Temperature Sensor Handbook
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Figure 5.2. This circuit performs same function circuit 5.1, designed cooling fan.
Low/High Controllers circuit Figure again uses LM56, this case always When circuit board's temperature low, runs relatively slow speed. When temperature exceeds 50°C, speed increases maximum value. with circuits Figures 5.2, OUT2 second logic-level output that indicates that LM56's temperature greater than 70°C. Again, this second logic output needed, VREF pins connected together resistors replaced single resistor whose value equal their resistances. Another variation this approach uses MOSFET turn lower temperature threshold, fan's speed control input increase fan's speed when second threshold exceeded.
Figure 5.3. control some fans without adding power device system. This circuit controls fan's speed taking "third lead" when temperature high. This increases fan's speed provide additional cooling.
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Temperature Sensor Handbook
Figure 5.4. combining approaches shown previous circuits, build controller that turns temperature, then increases speed temperature rises above second threshold.
Digital Temperature Monitor Temperature sensors with digital ideally suited motherboard applications. LM75 shown here communicates with host bus, which 2-wire communications protocol. LM75 internal temperature sensor delta-sigma ADC, which continuously converts device's temperature into data. This data read time over interface. addition, host program threshold temperature into LM75 that will cause O.S. produce logic output indicating excessive temperature condition. This output used interrupt processor that take action (such increasing speed, decreasing clock speed, shutting down system) protect system. best results, LM75 should mounted close possible microprocessor, either motherboard next processor, even under processor package. many systems, several LM75s distributed throughout chassis continuously monitor number potential spots. eight LM75s connected same selecting eight different addresses with pins
Temperature Sensor Handbook
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Figure 5.5. Place LM75 near microprocessor monitor microprocessors temperature motherboard application. Temperature data read time over two-wire, compatible serial interface. LM75s share same serial their addresses different values using
Interfacing External Temperature Sensors
LM75-to-PC interface LM75 allows acquire temperature data through parallel printer port with minimal circuitry shown Figure 5.6. LM75 gets power from line parallel printer port. jumpers address pins allow select LM75's address. eight LM75s connected same port selected according chosen address.
1N5712
Inside Personal Computer
addr
LM75
ReadBack Register
addr+1
Figure 5.6. PC-Based Temperature Acquisition Parallel Printer Port.
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Temperature Sensor Handbook
Isolated LM75-to-PC couple LM75 digital output temperature sensor through isolated interface shown Figure 5.7. Electrically isolating sensor allows operation situations exposed high common-mode voltages; could useful breaking ground loops. Note that (clock) line bi-directional. LM75 slave, input only. O.S. optocoupler optional needed only desired monitor O.S. Provide isolated supply voltage, either DC-DC converter battery. LM75 will operate from typically requires 250µA, while require 7-10mA each (the LEDs require about 700µA, only when active), total current drain about 30mA.
Supply Isolated DC-DC Converter
From Host Processor 4.3k
LM75 Desired 4.3k
4.3k
4.3k
Optocouplers (IC1-IC5 HCPL2300 D1-D4 1N5712
4.3k
Figure 5.7. Isolated PC-Based Thermometer.
Low-Power Systems
Low-Voltage, Low-Power Temperature Sensor with "Shutdown" Battery-operated portable equipment such cordless wireless telephones must operate from very supply voltages draw minimal current from supply order maximize battery life. circuit shown Figure LM60 temperature sensor, which been optimized portable applications operating from little 2.7V. battery-powered systems, however, even LM60's 140µA maximum supply current
Temperature Sensor Handbook
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hasten battery discharge device operating full-time. Therefore, LM60 shown here being powered CMOS logic gate, which means that LM60's supply connection serves "shutdown" pin. Because temperature changes slowly, measured quickly, LM60 powered small percentage total operating time, second every minutes, providing "quick" response changes temperature, using only around average current.
SHUTDOWN Logic device output LM60
Figure 5.8. 2.7V Temperature Sensor Operating From Logic Gate.
Battery Management Battery charging circuits range complexity from simple voltage sources with current-limiting resistors sophisticated systems based "smart batteries" that include microcontrollers, temperature sensors, ADCs, non-volatile memory store optimum charging data usage history. charge status battery measured using terminal voltage tracking charge flowing cells. Fast chargers NiCad NiMH batteries often also rely cell temperature help determine when terminate charging. NiCad batteries, charging endothermic process, NiCad battery pack will either remain same temperature cool slightly during charging. When battery becomes overcharged, temperature will begin rise relatively quickly, indicating that charging current should turned (see Figure 5.9a). Charging exothermic process NiMH batteries, temperature increases slowly during entire charge cycle. either kind nickel-based battery, both voltage temperature often monitored avoid damage from overcharging. However, NiMH batteries change cell voltage much slower than NiCd batteries, temperature becomes primary indicator overcharging.
Cell Voltage
Charge (%C)
Cell Temperature (°C)
Charge (%C)
Figure 5.9. Typical NiCd Fast Charging Curves. Note that both cell voltage cell temperature provide indication overcharging.
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Temperature Sensor Handbook
Power" Battery Temperature Monitors Figure 5.10 shows temperature sensor housed battery pack charge control safety enhancement. LM234 produces output current that proportional absolute temperature (1µA/°K). This current converted voltage connecting LM234's output external resistor, which located host system, battery charger, shown here. With resistor, VTEMP 10mV/°K. using external break current path, current drain sensor drops zero when temperature being monitored. Sensor current drain also drops zero when battery unplugged from charger, when plugged into charger that power, thus preventing accidental battery discharge.
100k LM234 1µA/°k 10mV/°k VTemp monitoring control circuitry
Battery Pack
"Intelligent" Charger
Figure 5.10. This battery pack temperature sensor uses power unless (located either charger, shown here, "load system") turned This helps prevent accidental battery discharge.
Figure 5.11 shows another power" battery pack temperature sensor circuit, this using LM235 twoterminal temperature sensor. LM235 behaves like two-terminal shunt voltage reference with 10mV/°K temperature coefficient. resistor positive voltage develops current power LM235. this circuit, LM235 battery pack, external resistor charger. LM235 operates nominal current 1mA, output voltage (2.98V nominal 25°C) drives ADC. resolution depends desired sensitivity temperature changes. With 8-bit shown here, 1LSB corresponds change temperature. temperature range accurate measurements -23°C +125°C. more resolution needed, 10-bit converter will have 1LSB transition every 0.25°C.
Temperature Sensor Handbook
-21-
Charging Current Source R4** Good Thermal Coupling 1.1k LM335 9.53k LM4041-1.2 Battery Pack "Intelligent" Charger *Choose 1.35mA nominal current; text **See Text Choose near 4.5V LM4041-2.5 VREF+ R5** ADC10732 microcontroller
Figure 5.11. Voltage-Output Battery Pack Temperature Sensor
Audio
Audio Power Amplifier Heat Sink Temperature Detector Controller Figure 5.12 shows overtemperature detector power devices. this example, audio power amplifier bolted heat sink LM35 Celsius temperature sensor either glued heat sink near power amplifier, mounted printed circuit board opposite side from heat sink heat sink mounted flat against side printed circuit board. comparators output goes heat sink temperature rises above threshold voltage reference. This fault detection output from comparator used turn cooling fan. provide hysteresis prevent from rapidly cycling off. circuit shown designed turn when heat sink temperature exceeds about 80°C, turn when heat sink temperature falls below about 60°C. similar circuit shown Figure 5.13. this circuit, sensor, voltage reference, comparator replaced LM56. turns about 80°C, LM56's built-in hysteresis causes turn again when sensors temperature drops below about 75°C.
+12V Thermally LM3886 Connected +28V -28V 3.3µF film 10µF Audio 560k LM4041-1.2 LM35 NDS9410 LMC7211
Figure 5.12. this typical monolithic temperature sensor application, sensor leads attached audio power amplifier IC2's heat sink. When heat sinks temperature rises above 60°C threshold temperature, comparator IC3's output goes high, turning cooling fan.
-22-
Temperature Sensor Handbook
100k Thermally Connected +28V LM3886 -28V 3.3µF film 10µF 9.76K Audio
LM56
VREF
NDS356P
1.250V Reference
MC05J3 COMAIRROTRON FBK04F05L Panasonic
Temperature VTEMP Sensor
Figure 5.13. This circuit's function similar that circuit above, except that sensor, comparator, voltage reference integrated within LM56. this circuit, turns 80°C 75°C.
Other Applications
Two-Wire Temperature Sensor When sensing temperature remote location, desirable minimize number wires between sensor main circuit board. three-terminal sensor needs three wires power, ground, output signal; going wires means that power signal must coexist same wires. twoterminal sensor like LM334 LM335, these devices produce output signal that proportional absolute temperature, which inconvenient. need output signal proportional degrees must have more than wires, circuit Figure 5.14 good solution. sensors output voltage power transmitted signal. power source sensor sine-wave oscillator coupled two-wire line through blocking capacitor LM45 sensor, comprise half-wave voltage-doubler rectifier that provides power sensor. isolates sensors output from load capacitance, couples output signal line. protect sensors output from two-wire line. output line, form low-pass filter remove from output signal. prevents current from flowing which would attenuate temperature signal. output should drive high-impedance load (preferably 100k greater).
Temperature Sensor Handbook
-23-
6.8k 200pF
6.8k 200pF
6.8k 200pF
LM6218 1N914
0.01µF
0.01µF 100mH Two-wire line Output 0.1µF
0.1µF
100mH
LM45
0.1µF
Figure 5.14. This two-wire remote temperature sensor transmits output sensor without reducing accuracy.
4-to-20mA Current Transmitter (0°C 100°C) This circuit uses LM45 LM35 temperature sensor develop 4-to-20mA current. temperature sensors output drive augmented drive 62.5 load; this provides 160µA/°C transfer function slope required develop 4-to-20mA output current 100°C temperature range. LM317 voltage regulator load resistors draw about 2.8mA from supply. remaining 1.2mA obtained adjusting potentiometer develop offset voltage temperature sensors ground pin.
+10V 4.7k 2N2907 OFFSET ADJUST
LM45
LM317
62.5 0.5%
Figure 5.15. 4-20mA Current Transmitter Temperature Sensor
-24-
Temperature Sensor Handbook
Multi-Channel Temperature-to-Digital Converter This circuit implements low-cost system measuring temperature several points within system converting temperature readings digital form. With components shown here, LM45 temperature sensors drive separate inputs ADC08019 8-bit, 19-channel with serial (microwire, SPI) data interface. tiny SOT-23 sensor packages allow designer place sensors virtually location within system. 1.28V reference voltage chosen provide conversion scale 1LSB=5mV=0.5°C, with full-scale equal 128°C. network sensors' outputs provide protection against oscillation capacitive loads cables) encountered, also help filter output noise. reference voltage manually adjusted 1.28V with potentiometer, potentiometer replaced with fixed resistor. values will used, 3.3k resistor will work. better accuracy, resistors; then replaced 3.24k resistor.
3.9K 100K SCLK
LM45
LM4041-ADJ
ADC0819
CH10 CH11 CH12 CH13 CH14 CH15 CH16 CH17 CH18
Figure 5.16. 19-Channel Temperature-to-Digital Converter. Only LM45 temperature sensor shown. LM45 connected each ADC0819's inputs.
Oven Temperature Controllers circuit Figure 5.17 operates single supply controls temperature oven. shown, circuit keeps oven temperature 75°C, which ideal most types quartz crystals. inverting input amplifier (1/2 LM392 amplifier/comparator dual) comes from LM335 temperature sensor, which should good thermal contact with heater, non-inverting input
Temperature Sensor Handbook
-25-
output voltage divider from LM4040-4.1 voltage reference. With divider components shown, non-inverting input 3.48V, which equal LM335's output 75°C. amplifier gain difference between measured temperature set-point. output modulates duty cycle oscillator built around comparator When oven cold, output high, which charges capacitor forces C1's output low. This turns delivers full power heater. oven temperature approaches set-point, A1's output goes lower, adjusts oscillators duty cycle servo oven temperature near set-point.
1.5k LM335 LM4040 -4.1 100k 0.001 6.8k 100k HEATER 2N5023 100k 4.7µF SOLID TANTALUM
2.7k
100k
100k
THERMAL FEEDBACK LM392 amplifier-comparator
Figure 5.17. Oven Controller
Isolated Temperature-to-Frequency Converter simple transmit analog information across isolation barrier first convert analog signal into frequency. frequency then easily counted other side isolation barrier microcontroller. Figure 5.18 shows simple implementing this. LM45's analog output, which proportional temperature, drives input LM131 configured converter. Over temperature range 2.5°C 100°C, LM45 produces output voltages from 25mV which causes LM131 develop output frequencies from 25Hz 1kHz.
5.8k 100k 0.01µF 100k
Full Scale Adjust
4N28 fOUT
LM45
LM131
0.01µF Tempco
Figure 5.18. Isolated Temperature-to-Frequency Converter
-26-
Temperature Sensor Handbook
Datasheets
Access National Semiconductor's temperature sensor datasheets/pricing/demo board kits/free samples internet!
call your local Distributor/Sales Office/Customer Response Center.
-28-
Temperature Sensor Handbook
LM34 LM34A LM34C LM34CA LM34D Precision Fahrenheit Temperature Sensors
December 1994
LM34 LM34A LM34C LM34CA LM34D Precision Fahrenheit Temperature Sensors
General Description
LM34 series precision integrated-circuit temperature sensors whose output voltage linearly proportional Fahrenheit temperature LM34 thus advantage over linear temperature sensors calibrated degrees Kelvin user required subtract large constant voltage from output obtain convenient Fahrenheit scaling LM34 does require external calibration trimming provide typical accuracies room temperature over full temperature range cost assured trimming calibration wafer level LM34's output impedance linear output precise inherent calibration make interfacing readout control circuitry especially easy used with single power supplies with plus minus supplies draws only from supply very self-heating less than still LM34 rated operate over temperature range while LM34C rated range with improved accuracy) LM34 series available packaged hermetic TO-46 transistor packages while LM34C LM34CA LM34D also available plastic TO-92 transistor package LM34D also available 8-lead surface mount small outline package LM34 complement LM35 (Centigrade) temperature sensor
Features
Calibrated directly degrees Fahrenheit Linear scale factor accuracy guaranteed Rated full range Suitable remote applications cost wafer-level trimming Operates from volts Less than current drain self-heating still Nonlinearity only typical Low-impedance output load
Connection Diagrams
TO-46 Metal Package TO-92 Plastic Package SO-8 Small Outline Molded Package
6685-1
6685
Case connected negative (GND)
Order Numbers LM34H LM34AH LM34CH LM34CAH LM34DH Package Number H03H
Order Number LM34CZ LM34CAZ LM34DZ Package Number Z03A
6685
View
Connection
Order Number LM34DM Package Number M08A
Typical Applications
6685
FIGURE Basic Fahrenheit Temperature Sensor
6685
TRI-STATE registered trademark National Semiconductor Corporation C1995 National Semiconductor Corporation 6685
FIGURE Full-Range Fahrenheit Temperature Sensor
RRD-B30M75 Printed
Temperature Sensor Handbook
-29-
LM35/LM35A/LM35C/LM35CA/LM35D Precision Centigrade Temperature Sensors
September 1997
LM35/LM35A/LM35C/LM35CA/LM35D Precision Centigrade Temperature Sensors
General Description
LM35 series precision integrated-circuit temperature sensors, whose output voltage linearly proportional Celsius (Centigrade) temperature. LM35 thus advantage over linear temperature sensors calibrated Kelvin, user required subtract large constant voltage from output obtain convenient Centigrade scaling. LM35 does require external calibration trimming provide typical accuracies 1/4°C room temperature 3/4°C over full +150°C temperature range. cost assured trimming calibration wafer level. LM35's output impedance, linear output, precise inherent calibration make interfacing readout control circuitry especially easy. used with single power supplies, with plus minus supplies. draws only from supply, very self-heating, less than 0.1°C still air. LM35 rated operate over -55° +150°C temperature range, while LM35C rated -40° +110°C range (-10° with improved accuracy). LM35 series available packaged hermetic TO-46 transistor packages, while LM35C, LM35CA, LM35D also available plastic TO-92 transistor package. LM35D also available 8-lead surface mount small outline package plastic TO-220 package.
Features
Calibrated directly Celsius (Centigrade) Linear 10.0 mV/°C scale factor 0.5°C accuracy guaranteeable +25°C) Rated full -55° +150°C range Suitable remote applications cost wafer-level trimming Operates from volts Less than current drain self-heating, 0.08°C still Nonlinearity only 1/4°C typical impedance output, load
Typical Applications
DS005516-4 DS005516-3
FIGURE Basic Centirade Temperature Sensor (+2°C +150°C)
Choose -VS/50 +1,500 +150°C +250 +25°C -550 -55°C
FIGURE Full-Range Centigrade Temperature Sensor
TRI-STATE registered trademark National Semiconductor Corporation.
1997 National Semiconductor Corporation
DS005516
www.national.com
-30-
Temperature Sensor Handbook
LM45B LM45C SOT-23 Precision Centigrade Temperature Sensors
1995
LM45B LM45C SOT-23 Precision Centigrade Temperature Sensors
General Description
LM45 series precision integrated-circuit temperature sensors whose output voltage linearly proportional Celsius (Centigrade) temperature LM45 does require external calibration trimming provide accuracies room temperature over full temperature range cost assured trimming calibration wafer level LM45's output impedance linear output precise inherent calibration make interfacing readout control circuitry especially easy used with single power supply with plus minus supplies draws only from supply very self-heating less than still LM45 rated operate over temperature range
Portable Medical Instruments HVAC Power Supply Modules Disk Drives Computers Automotive
Features
Applications
Battery Management Machines Printers
Calibrated directly Celsius (Centigrade) Linear scale factor accuracy guaranteed Rated full range Suitable remote applications cost wafer-level trimming Operates from Less than current drain self-heating still Nonlinearity only over temp impedance output load
Connection Diagram
SOT-23 Order Number LM45BIM3 LM45BIM3X
11754
SOT-23 Device Marking
Supplied Units Tape Reel 3000 Units Tape Reel Units Tape Reel 3000 Units Tape Reel
View Package Number M03B (JEDEC Registration TO-236AB)
LM45CIM3 LM45CIM3X
Typical Applications
11754
FIGURE Basic Centigrade Temperature Sensor
Choose VOUT Temp VOUT
11754
FIGURE Full-Range Centigrade Temperature Sensor (b20
C1995 National Semiconductor Corporation
11754
RRD-B30M75 Printed
Temperature Sensor Handbook
-31-
LM50B LM50C SOT-23 Single-Supply Centigrade Temperature Sensor
June 1996
LM50B LM50C SOT-23 Single-Supply Centigrade Temperature Sensor
General Description
LM50 precision integrated-circuit temperature sensor that sense temperature range using single positive supply LM50's output voltage linearly proportional Celsius (Centigrade) temperature offset offset allows reading negative temperatures without need negative supply ideal output voltage LM50 ranges from temperature range LM50 does require external calibration trimming provide accuracies room temperature over full temperature range Trimming calibration LM50 wafer level assure cost high accuracy LM50's linear output offset factory calibration simplify circuitry required single supply environment where reading negative temperatures required Because LM50's quiescent current less than self-heating limited very still
Battery Management Automotive Machines Printers Portable Medical Instruments HVAC Power Supply Modules
Features
Applications
Calibrated directly Celsius (Centigrade) Linear scale factor accuracy guaranteed Specified full range Suitable remote applications cost wafer-level trimming Operates from Less than current drain self-heating less than still Nonlinearity less than over temp
Computers Disk Drives
Connection Diagram
SOT-23 Order Number LM50BIM3 LM50CIM3 LM50BIM3X
12030-1
SOT-23 Device Marking
Supplied Units Tape Reel Units Tape Reel 3000 Units Tape Reel 3000 Units Tape Reel
View Package Number M03B (JEDEC Registration TO-236AB)
LM50CIM3X
Typical Application
12030
FIGURE Full-Range Centigrade Temperature Sensor (b40
C1996 National Semiconductor Corporation
12030
RRD-B30M76 Printed
http
national
-32-
Temperature Sensor Handbook
LM56 Dual Output Power Thermostat
September 1996
LM56 Dual Output Power Thermostat
General Description
LM56 precision power thermostat. stable temperature trip points (VT1 VT2) generated dividing down LM56 1.250V bandgap voltage reference using external resistors. LM56 digital outputs. OUT1 goes when temperature exceeds goes HIGH when temperature goes below (T1-THYST). Similarly, OUT2 goes when temperature exceeds goes HIGH when temperature goes below (T2-THYST). THYST internally typical hysteresis. LM56 available 8-lead Mini-SO8 surface mount package 8-lead small outline package. Internal temperature sensor internal comparators with hysteresis Internal voltage reference Currently available 8-pin plastic package Future availability 8-pin Mini-SO8 package
Specifications
Power Supply Voltage Power Supply Current VREF Hysteresis Temperature Internal Temperature Sensor Output Voltage (+6.20 mV/°C +395 Temperature Trip Point Accuracy: LM56BIM +25°C +25°C +85°C -40°C +125°C LM56CIM 2.7V-10V (max) 1.250V (max)
Applications
Microprocessor Thermal Management Appliances Portable Battery Powered 3.0V Systems Control Industrial Process Control HVAC Systems Remote Temperature Sensing Electronic System Protection
(max) (max) (max)
(max) (max) (max)
Features
Digital outputs support logic levels
Simplified Block Diagram Connection Diagram
DS012893-2
DS012893-1
Order Number Package Number Transport Media
LM56BIM LM56BIMX M08A SOP-8 Units Rail M08A SOP-8 2500 Units Tape Reel
LM56CIM LM56CIMX M08A SOP-8 Units Rail M08A SOP-8 2500 Units Tape Reel
LM56BIMM MUA08A MSOP-8 Units Rail
LM56BIMMX MUA08A MSOP-8 3500 Units Tape Reel
LM56CIMM MUA08A MSOP-8 Units Rail
LM56CIMMX MUA08A MSOP-8 3500 Units Tape Reel
1997 National Semiconductor Corporation
DS012893
www.national.com
Temperature Sensor Handbook
-33-
LM60B LM60C SOT-23 Temperature Sensor
April 1996
LM60B LM60C SOT-23 Temperature Sensor
General Description
LM60 precision integrated-circuit temperature sensor that sense temperature range while operating from single supply LM60's output voltage linearly proportional Celsius (Centigrade) temperature offset offset allows reading negative temperatures without need negative supply nominal output voltage LM60 ranges from 1205 temperature range LM60 calibrated provide accuracies room temperature over full temperature range LM60's linear output offset factory calibration simplify external circuitry required single supply environment where reading negative temperatures required Because LM60's quiescent current less than self-heating limited very still Shutdown capability LM60 intrinsic because inherent power consumption allows powered directly from output many logic gates
Power Supply Modules Battery Management Machines Printers HVAC Disk Drives Appliances
Features
Calibrated linear scale factor Rated full range Suitable remote applications
Specifications
Applications
(max) Accuracy (max) Accuracy (max) Accuracy Temperature Slope Power Supply Voltage Range Current Drain (max) (max) Nonlinearity Output Impedance 800X (max)
Cellular Phones Computers
Connection Diagram
SOT-23
Typical Application
12681
View Package Number MA03B Order Information SOT-23 Device Marking
12681
Temperature Typical
1205 1049
Order Number LM60BIM3 LM60BIM3X LM60CIM3 LM60CIM3X
Supplied Units Tape Reel 3000 Units Tape Reel Units Tape Reel 3000 Units Tape Reel
FIGURE Full-Range Centigrade Temperature Sensor (b40 Operating from Single Li-Ion Battery Cell
C1996 National Semiconductor Corporation
12681
RRD-B30M56 Printed
-34-
Temperature Sensor Handbook
LM75 Digital Temperature Sensor Thermal Watchdog with Two-Wire Interface
October 1997 April 1997
LM75 Digital Temperature Sensor Thermal Watchdog with Two-Wire Interface
General Description
LM75 temperature sensor, Delta-Sigma analog-to-digital converter, digital over-temperature detector with interface. host query LM75 time read temperature. open-drain Overtemperature Shutdown (O.S.) output becomes active when temperature exceeds programmable limit. This operate either "Comparator" "Interrupt"mode. host program both temperature alarm threshold (TOS) temperature which alarm condition goes away (THYST). addition, host read back contents LM75's THYST registers. Three pins (A0, available address selection. sensor powers Comparator mode with default thresholds 80°C 75°C THYST. LM75's 3.0V 5.5V supply voltage range, supply current interface make ideal wide range applications. These include thermal management protection applications personal computers, electronic test equipment, office electronics. Separate open-drain output operates interrupt comparator/thermostat output Register readback capability Power defaults permit stand-alone operation thermostat Shutdown mode minimize power consumption LM75s connected single
Specifications
Supply Voltage Supply Current operating shutdown Temperature Accuracy -25°C 100°C -55°C 125°C 3.0V 5.5V (typ) (max) (typ)
2°C(max) 3°C(max)
Applications
System Thermal Management Personal Computers Office Electronics Electronic Test Equipment
Features
SOP-8 Mini SOP-8 (MSOP) packages save space interface
Simplified Block Diagram
DS012658-1
registered trademark Philips Corporation.
1997 National Semiconductor Corporation
DS012658
www.national.com
TemperatureSensorHandbook
-35-
General Description
LM77 digital temperature sensor thermal window comparator with Serial interface. window-comparator architecture LM77 eases design temperature control systems conforming ACPI (Advanced Configuration Power Interface) specification personal computers. open-drain Interrupt (Int) output becomes active whenever temperature goes outside programmable window, while separate Overtemperature Shutdown (O.S.) output becomes active when temperature exceeds programmable overtemperature limit. These outputs operate either comparator event mode. host program both upper lower limits window well overtemperature shutdown limit. Programmable hysterisis well fault queue available minimize false tripping. pins (A0, available address selection. sensor powers with default thresholds THYST, 10°C TLOW, 64°C THIGH, 80°C TOS. LM77's 2.7V 5.5V supply voltage range, Serial interface, 9-bit sign output, full-scale range over 150°C make ideal wide range applications. These include thermal management protection applications personal computers, electronic test equipment, office electronics, automotive, HVAC applications.
Advance Information
9/29/97
LM77 9-Bit +Sign Digital Temperature Sensor Thermal Window Comparator with Two-Wire Interface
Features
Window comparison simplifies design ACPI compliant temperature monitoring control. Serial interface Separate open-drain outputs Interrupt Overtemperature Shutdown Shutdown mode minimize power consumption. LM77's connected single bus. 9-bit sign output; full-scale range over
Specifications
2.7V 5.5V (typ) (max) shutdown (typ) sTemperature Accuracy -25°C 100°C ±2°C(max) -55° 125° ±3°C(max) Supply Voltage Supply Current operating
Applications
System Thermal Management Personal Computers Office Electronics Electronic Test Equipment Automotive HVAC
Simplified Block Diagram
2.7V 5.5V 8-Bit Sign Temperature-to-Digital Converter O.S. HIGH
TLOW
HIGH Serial Interface Storage Registers
registered trademark Philips Corporation
-36-
TemperatureSensorHandbook
LM134 LM234 LM334 3-Terminal Adjustable Current Sources
March 1995
LM134 LM234 LM334 3-Terminal Adjustable Current Sources
General Description
LM134 LM234 LM334 3-terminal adjustable current sources featuring range operating current excellent current regulation wide dynamic voltage range Current established with external resistor other parts required Initial current accuracy LM134 LM234 LM334 true floating current sources with separate power supply connections addition reverse applied voltages will draw only dozen microamperes current allowing devices both rectifier current source applications sense voltage used establish operating current LM134 directly proportional absolute temperature simplest external resistor connection then generates current with temperature dependence Zero drift operation obtained adding extra resistor diode Applications current sources include bias networks surge protection power reference ramp generation driver temperature sensing LM134-3 LM234-3 LM134-6 LM234-6 specified true temperature sensors with guaranteed initial accuracy respectively These devices ideal remote sense applications because series resistance long wire runs does affect accuracy addition only wires required LM134 guaranteed over temperature range LM234 from LM334 from These devices available TO-46 hermetic TO-92 SO-8 plastic packages
Features
Operates from current regulation Programmable from True 2-terminal operation Available fully specified temperature sensor initial accuracy
Connection Diagrams
SO-8 Surface Mount Package SO-8 Alternative Pinout Surface Mount Package TO-46 Metal Package TO-92 Plastic Package
5697 5697
Bottom View Order Number LM334Z LM234Z-3 LM234Z-6 Package Number Z03A
Bottom View
5697 5697-24
Order Number LM334M Package Number M08A
Order Number LM334SM Package Number M08A
electrically connected case
Typical Application
Basic 2-Terminal Current Source
Order Number LM134H LM134H-3 LM134H-6 LM234H LM334H Package Number H03H
5697
C1995 National Semiconductor Corporation
5697
RRD-B30M75 Printed
Temperature Sensor Handbook
-39-
LM135 LM235 LM335 LM135A LM235A LM335A Precision Temperature Sensors
February 1995
LM135 LM235 LM335 LM135A LM235A LM335A Precision Temperature Sensors
General Description
LM135 series precision easily-calibrated integrated circuit temperature sensors Operating 2-terminal zener LM135 breakdown voltage directly proportional absolute temperature With less than dynamic impedance device operates over current range with virtually change performance When calibrated LM135 typically less than error over temperature range Unlike other sensors LM135 linear output Applications LM135 include almost type temperature sensing over temperature range impedance linear output make interfacing readout control circuitry especially easy LM135 operates over temperature range while LM235 operates over temperature range LM335 operates from LM135 LM235 LM335 available packaged hermetic TO-46 transistor packages while LM335 also available plastic TO-92 packages
Features
Directly calibrated Kelvin initial accuracy available Operates from Less than dynamic impedance Easily calibrated Wide operating temperature range overrange cost
Schematic Diagram
5698
Connection Diagrams
TO-92 Plastic Package SO-8 Surface Mount Package TO-46 Metal Package
5698-8
Bottom View Order Number LM335Z LM335AZ Package Number Z03A
5698
5698
Order Number LM335M LM335AM Package Number M08A
Bottom View
Case connected negative
Order Number LM135H LM135H-MIL LM235H LM335H LM135AH LM235AH LM335AH Package Number H03H
RRD-B30M115 Printed
C1995 National Semiconductor Corporation
5698
-40-
Temperature Sensor Handbook

andbook Sensor emperatu ductor's Semicon Introduction this H

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