LM135/LM235/LM335, LM135A/LM235A/LM335A Precision Temperature Sensors General Description The LM135 series are precision, easily-calibrated, integrated circuit temperature sensors. Operating as a 2-terminal zener, the LM135 has a breakdown voltage directly proportional to absolute temperature at +10 mV/°K. With less than 1Ω dynamic impedance the device operates over a current range of 400 μA to 5 mA with virtually no change in performance. When calibrated at 25°C the LM135 has typically less than 1° C error over a 100°C temperature range. Unlike other sensors the LM135 has a linear output. Applications for the LM135 include almost any type of temperature sensing over a −55°C to 150°C temperature range. The low impedance and linear output make interfacing to readout or control circuitry especially easy. The LM135 operates over a −55°C to 150°C temperature range while the LM235 operates over a −40°C to 125°C tem- perature range. The LM335 operates from −40°C to 100°C. The LM135/LM235/LM335 are available packaged in hermetic TO-46 transistor packages while the LM335 is also available in plastic TO-92 packages. Features ■ ■ ■ ■ ■ ■ ■ ■ Directly calibrated in °Kelvin 1°C initial accuracy available Operates from 400 μA to 5 mA Less than 1Ω dynamic impedance Easily calibrated Wide operating temperature range 200°C overrange Low cost Schematic Diagram 569801 © 2008 National Semiconductor Corporation 5698 www.national.com LM135/LM235/LM335, LM135A/LM235A/LM335A Precision Temperature Sensors December 17, 2008 LM135/LM235/LM335, LM135A/LM235A/LM335A Specified Operating Temp. Range Continuous Absolute Maximum Ratings (Note 4) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Reverse Current Forward Current Storage Temperature 8-Pin SOIC Package TO-92 Package TO-46 Package LM135, LM135A −55°C to 150°C LM235, LM235A −40°C to 125°C LM335, LM335A −40°C to 100°C Lead Temp. (Soldering, 10 seconds) 8-Pin SOIC Package: Vapor Phase (60 seconds): Infrared (15 seconds): TO-92 Package: TO-46 Package: 15 mA 10 mA −65°C to 150°C −60°C to 150°C −60°C to 180°C Temperature Accuracy Intermittent (Note 2) 150°C to 200°C 125°C to 150°C 100°C to 125°C 300°C 215°C 220°C 260°C 300°C (Note 1) LM135/LM235, LM135A/LM235A Parameter LM135A/LM235A Conditions LM135/LM235 Units Min Typ Max Min Typ Max 2.97 2.98 2.99 2.95 2.98 3.01 V TC = 25°C, IR = 1 mA 0.5 1 1 3 °C Uncalibrated Temperature Error TMIN ≤ TC ≤ TMAX, IR = 1 mA 1.3 2.7 2 5 °C Temperature Error with 25°C TMIN ≤ TC ≤ TMAX, IR = 1 mA 0.3 1 0.5 1.5 °C Operating Output Voltage TC = 25°C, IR = 1 mA Uncalibrated Temperature Error Calibration Calibrated Error at Extended TC = TMAX (Intermittent) 2 2 °C Temperatures Non-Linearity IR = 1 mA Temperature Accuracy 0.3 0.5 0.3 1 °C (Note 1) LM335, LM335A Parameter LM335A Conditions LM335 Units Min Typ Max Min Typ Max 2.95 2.98 3.01 2.92 2.98 3.04 V Operating Output Voltage TC = 25°C, IR = 1 mA Uncalibrated Temperature Error TC = 25°C, IR = 1 mA 1 3 2 6 °C Uncalibrated Temperature Error TMIN ≤ TC ≤ TMAX, IR = 1 mA 2 5 4 9 °C Temperature Error with 25°C TMIN ≤ TC ≤ TMAX, IR = 1 mA 0.5 1 1 2 °C Calibration Calibrated Error at Extended TC = TMAX (Intermittent) 2 2 °C Temperatures Non-Linearity IR = 1 mA Electrical Characteristics Parameter 0.3 1.5 0.3 1.5 °C (Note 1) LM135/LM235 LM135A/LM235A Conditions Min Operating Output Voltage 400 μA ≤ IR ≤ 5 mA Change with Current At Constant Temperature Dynamic Impedance IR = 1 mA Output Voltage Temperature Coefficient Typ Max 2.5 10 LM335 LM335A Min Units Typ Max 3 14 mV 0.5 0.6 Ω +10 +10 mV/°C Time Constant Still Air 100 ft/Min Air Stirred Oil 80 10 1 80 10 1 sec sec sec Time Stability TC = 125°C 0.2 0.2 °C/khr www.national.com 2 Note 2: Continuous operation at these temperatures for 10,000 hours for H package and 5,000 hours for Z package may decrease life expectancy of the device. 8-Pin SOIC TO-92 θJA (Junction to Ambient) Thermal Resistance 165°C/W 202°C/W 400°C/W TO-46 θJC (Junction to Case) N/A 170°C/W N/A Note 4: Refer to RETS135H for military specifications. Connection Diagrams 8-Pin SOIC Surface Mount Package TO-92 Plastic Package TO-46 Metal Can Package* 569808 Bottom View 569825 569826 *Case is connected to negative pin Top View Bottom View Ordering Information Package Part Number LM335AM 8-Pin SOIC LM335AMX LM335M LM335MX TO-92 TO-46 Package Marking Transport Media NSC Drawing 95 Units/Rail LM335AM 2.5k Units Tape and Reel 95 Units/Rail LM335M M08A 2.5k Units Tape and Reel LM335AZ LM335AZ 1800 Bag LM335Z LM335Z 1800 Bag LM135AH LM135AH 1000 Bag LM135H LM135H 1000 Bag LM235AH LM235AH 1000 Bag LM235H LM235H 1000 Bag LM335AH LM335AH 1000 Bag LM335H LM335H 1000 Bag 3 Z03Z H03H www.national.com LM135/LM235/LM335, LM135A/LM235A/LM335A Note 1: Accuracy measurements are made in a well-stirred oil bath. For other conditions, self heating must be considered. LM135/LM235/LM335, LM135A/LM235A/LM335A Typical Performance Characteristics Reverse Voltage Change Calibrated Error 569827 569828 Reverse Characteristics Response Time 569829 569830 Dynamic Impedance Noise Voltage 569831 www.national.com 569832 4 Thermal Time Constant 569834 569833 Thermal Response in Still Air Thermal Response in Stirred Oil Bath 569836 569835 Forward Characteristics 569837 5 www.national.com LM135/LM235/LM335, LM135A/LM235A/LM335A Thermal Resistance Junction to Air LM135/LM235/LM335, LM135A/LM235A/LM335A Calibrated Sensor Application Information CALIBRATING THE LM135 Included on the LM135 chip is an easy method of calibrating the device for higher accuracies. A pot connected across the LM135 with the arm tied to the adjustment terminal allows a 1-point calibration of the sensor that corrects for inaccuracy over the full temperature range. This single point calibration works because the output of the LM135 is proportional to absolute temperature with the extrapolated output of sensor going to 0V output at 0°K (−273.15°C). Errors in output voltage versus temperature are only slope (or scale factor) errors so a slope calibration at one temperature corrects at all temperatures. The output of the device (calibrated or uncalibrated) can be expressed as: 569809 *Calibrate for 2.982V at 25°C Wide Operating Supply where T is the unknown temperature and To is a reference temperature, both expressed in degrees Kelvin. By calibrating the output to read correctly at one temperature the output at all temperatures is correct. Nominally the output is calibrated at 10 mV/°K. To insure good sensing accuracy several precautions must be taken. Like any temperature sensing device, self heating can reduce accuracy. The LM135 should be operated at the lowest current suitable for the application. Sufficient current, of course, must be available to drive both the sensor and the calibration pot at the maximum operating temperature as well as any external loads. If the sensor is used in an ambient where the thermal resistance is constant, self heating errors can be calibrated out. This is possible if the device is run with a temperature stable current. Heating will then be proportional to zener voltage and therefore temperature. This makes the self heating error proportional to absolute temperature the same as scale factor errors. Minimum Temperature Sensing WATERPROOFING SENSORS Meltable inner core heat shrinkable tubing such as manufactured by Raychem can be used to make low-cost waterproof sensors. The LM335 is inserted into the tubing about ½″ from the end and the tubing heated above the melting point of the core. The unfilled ½″ end melts and provides a seal over the device. Average Temperature Sensing 569810 569804 Typical Applications Basic Temperature Sensor 569818 569802 www.national.com 6 AWG 14 16 18 20 22 24 IR = 1 mA IR = 0.5 mA* FEET 4000 2500 1600 1000 FEET 8000 5000 3200 2000 1250 625 400 LM135/LM235/LM335, LM135A/LM235A/LM335A Remote Temperature Sensing 800 *For IR = 0.5 mA, the trim pot must be deleted. 569819 Wire length for 1°C error due to wire drop Isolated Temperature Sensor 569820 Simple Temperature Controller 569805 7 www.national.com LM135/LM235/LM335, LM135A/LM235A/LM335A Simple Temperature Control 569821 Ground Referred Fahrenheit Thermometer 569822 *Adjust R2 for 2.554V across LM336. Adjust R1 for correct output. Centigrade Thermometer 569823 *Adjust for 2.7315V at output of LM308 www.national.com 8 LM135/LM235/LM335, LM135A/LM235A/LM335A Fahrenheit Thermometer 569824 *To calibrate adjust R2 for 2.554V across LM336. Adjust R1 for correct output. THERMOCOUPLE COLD JUNCTION COMPENSATION Compensation for Grounded Thermocouple 569806 *Select R3 for proper thermocouple type THERMOCOUPLE J R3 (±1%) SEEBECK COEFFICIENT 377Ω 52.3 μV/°C T 308Ω 42.8 μV/°C K 293Ω 40.8 μV/°C S 45.8Ω 6.4 μV/°C Adjustments: Compensates for both sensor and resistor tolerances 1. Short LM329B 2. Adjust R1 for Seebeck Coefficient times ambient temperature (in degrees K) across R3. 3. Short LM335 and adjust R2 for voltage across R3 corresponding to thermocouple type. J 14.32 mV K 11.17 mV T 11.79 mV S 1.768 mV 9 www.national.com LM135/LM235/LM335, LM135A/LM235A/LM335A Single Power Supply Cold Junction Compensation 569811 *Select R3 and R4 for thermocouple type THERMOCOUPLE J R3 R4 SEEBECK COEFFICIENT 1.05K 385Ω 52.3 μV/°C T 856Ω 315Ω 42.8 μV/°C K 816Ω 300Ω 40.8 μV/°C S 128Ω 46.3Ω 6.4 μV/°C Adjustments: 1. Adjust R1 for the voltage across R3 equal to the Seebeck Coefficient times ambient temperature in degrees Kelvin. 2. Adjust R2 for voltage across R4 corresponding to thermocouple. J 14.32 mV T 11.79 mV K 11.17 mV S 1.768 mV www.national.com 10 LM135/LM235/LM335, LM135A/LM235A/LM335A Centigrade Calibrated Thermocouple Thermometer 569812 Terminate thermocouple reference junction in close proximity to LM335. Adjustments: 1. Apply signal in place of thermocouple and adjust R3 for a gain of 245.7. 2. Short non-inverting input of LM308A and output of LM329B to ground. 3. Adjust R1 so that VOUT = 2.982V @ 25°C. 4. Remove short across LM329B and adjust R2 so that VOUT = 246 mV @ 25°C. 5. Remove short across thermocouple. Fast Charger for Nickel-Cadmium Batteries 569813 †Adjust D1 to 50 mV greater VZ than D2. Charge terminates on 5°C temperature rise. Couple D2 to battery. Differential Temperature Sensor 569807 11 www.national.com LM135/LM235/LM335, LM135A/LM235A/LM335A Differential Temperature Sensor 569814 Variable Offset Thermometer‡ 569815 †Adjust for zero with sensor at 0°C and 10T pot set at 0°C *Adjust for zero output with 10T pot set at 100°C and sensor at 100°C ‡Output reads difference between temperature and dial setting of 10T pot www.national.com 12 LM135/LM235/LM335, LM135A/LM235A/LM335A Ground Referred Centigrade Thermometer 569816 Air Flow Detector* 569817 *Self heating is used to detect air flow Calibrated Temperature Error: The error between operating output voltage and case temperature at 10 mV/°K over a temperature range at a specified operating current with the 25°C error adjusted to zero. DEFINITION OF TERMS Operating Output Voltage: The voltage appearing across the positive and negative terminals of the device at specified conditions of operating temperature and current. Uncalibrated Temperature Error: The error between the operating output voltage at 10 mV/°K and case temperature at specified conditions of current and case temperature. 13 www.national.com LM135/LM235/LM335, LM135A/LM235A/LM335A Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin SOIC NS Package Number M08A TO-92 NS Package Z03A www.national.com 14 LM135/LM235/LM335, LM135A/LM235A/LM335A TO-46 NS Package Number H03H 15 www.national.com LM135/LM235/LM335, LM135A/LM235A/LM335A Precision Temperature Sensors Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage Reference www.national.com/vref Design Made Easy www.national.com/easy PowerWise® Solutions www.national.com/powerwise Solutions www.national.com/solutions Serial Digital Interface (SDI) www.national.com/sdi Mil/Aero www.national.com/milaero Temperature Sensors www.national.com/tempsensors Solar Magic® www.national.com/solarmagic Wireless (PLL/VCO) www.national.com/wireless Analog University® www.national.com/AU THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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