LM3911 Temperature Controller General Description The LM3911 is a highly accurate temperature measurement and/or control system for use over a b25§ C to a 85§ C temperature range. Fabricated on a single monolithic chip, it includes a temperature sensor, a stable voltage reference and an operational amplifier. The output voltage of the LM3911 is directly proportional to temperature in degrees Kelvin at 10 mV/§ K. Using the internal op amp with external resistors any temperature scale factor is easily obtained. By connecting the op amp as a comparator, the output will switch as the temperature transverses the set-point making the device useful as an on-off temperature controller. An active shunt regulator is connected across the power leads of the LM3911 to provide a stable 6.8V voltage reference for the sensing system. This allows the use of any power supply voltage with suitable external resistors. The input bias current is low and relatively constant with temperature, ensuring high accuracy when high source impedance is used. Further, the output collector can be returned to a voltage higher than 6.8V allowing the LM3911 to drive lamps and relays up to a 35V supply. The LM3911 uses the difference in emitter-base voltage of transistors operating at different current densities as the basic temperature sensitive element. Since this output depends only on transistor matching the same reliability and stability as present op amps can be expected. The LM3911 is available in two package styles, a metal can TO-46 and an 8-lead epoxy mini-DIP. In the epoxy package all electrical connections are made on one side of the device allowing the other 4 leads to be used for attaching the LM3911 to the temperature souce. The LM3911 is rated for operation over a b25§ C to a 85§ C temperature range. Features Y Y Y Y Y Y Y Uncalibrated accuracy g 10§ C Internal op amp with frequency compensation Linear output of 10 mV/§ K (10 mV/§ C) Can be calibrated in degrees Kelvin, Celsius or Fahrenheit Output can drive loads up to 35V Internal stable voltage reference Low cost Block Diagram Typical Applications Proportioning Temperature Controller Ground Referred Centigrade Thermometer Basic Temperature Controller * Output goes negative on temperature increase * Trims out initial zener tolerance. Set output to read C RS e (V a b 6.8V) kX TL/H/5701 – 1 Note 1: C1 determines proportioning frequency f & Note 2: R10 e 1 2R4 C1 lV a l a lVb l b 7V 0.0015A Note 3: Either Vb or V a can be ground. C1995 National Semiconductor Corporation TL/H/5701 RRD-B30M115/Printed in U. S. A. LM3911 Temperature Controller June 1994 Absolute Maximum Ratings Output Short Circuit Duration If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Supply Current (Externally Set) Output Collector Voltage, V a a Feedback Input Voltage Range Indefinite Operating Temperature Range b 25§ C to a 85§ C b 65§ C to a 150§ C Storage Temperature Range Lead Temperature (Soldering, 10 seconds) 260§ C 10 mA 36V 0V to a 7.0V Electrical Characteristics (Note 1) Parameter Conditions Min Typ Max Units Output Voltage TA eb25§ C, (Note 2) 2.36 2.48 2.60 V Output Voltage TA e a 25§ C, (Note 2) 2.88 2.98 3.08 V Output Voltage TA e a 85§ C, (Note 2) 3.46 3.58 3.70 V Linearity DT e 100§ C 0.5 2 % SENSOR Long-Term Stability 0.3 % Repeatability 0.3 % VOLTAGE REFERENCE Reverse Breakdown Voltage 1 mAsIzs5 mA 6.85 7.25 V Reverse Breakdown Voltage Change With Current 1 mAsIzs5 mA 6.55 10 35 mV 20 85 mV Dynamic Impedance Iz e 1 mA 3.0 X RMS Noise Voltage 10 Hzsfs10 kHz 30 mV Long Term Stability TA e a 85§ C 6.0 mV TA e a 25§ C 35 150 45 250 Temperature Stability OP AMP Input Bias Current Input Bias Current 2500 15000 nA nA Voltage Gain RL e 36k, V a a e 36V V/V Output Leakage Current TA e 25§ C (Note 3) 0.2 2 Output Leakage Current (Note 3) 1.0 8 Output Source Current VOUTs3.70 10 mA Output Sink Current 1VsVOUTs36V 2.0 mA mA mA Note 1: These specifications apply for b 25§ C s TA s a 85§ C and 0.9 mA s ISUPPLY s 1.1 mA unless otherwise specified; CL s 50 pF. Note 2: The output voltage applies to the basic thermometer configuration with the output and input terminals shorted and a load resistance of t 1.0 MX. This is the feedback sense voltage and includes errors in both the sensor and op amp. This voltage is specified for the sensor in a rapidly stirred oil bath. The output is referred to V a . Note 3: The output leakage current is specified with t 100 mV overdrive. Since this voltage changes with temperature, the voltage drive for turn-off changes and is defined as VOUT (with output and input shorted) b 100 mV. This specification applies for VOUT e 36V. Application Hints media will conduct the heat from the sensor. Also, there are many small heat sinks designed for transistors which will improve heat transfer to the sensor from the surrounding medium. A small finned clip-on heat sink is quite effective in free-air. It should be mentioned that the LM3911 die is on the base of the package and therefore coupling to the base is preferable. The internal reference regulator provides a temperature stable voltage for offsetting the output or setting a comparison point in temperature controllers. However, since this reference is at the same temperature as the sensor temperature, changes will also cause reference drift. For application where maximum accuracy is needed an external reference should be used. Of course, for fixed temperature controllers the internal reference is adequate. Although the LM3911 is designed to be totally trouble-free, certain precautions should be taken to insure the best possible performance. As with any temperature sensor, internal power dissipation will raise the sensor’s temperature above ambient. Nominal suggested operating current for the shunt regulator is 1.0 mA and causes 7.0 mW of power dissipation. In free, still, air this raises the package temperature by about 1.2§ K. Although the regulator will operate at higher reverse currents and the output will drive loads up to 5.0 mA, these higher currents will raise the sensor temperature to about 19§ K above ambient-degrading accuracy. Therefore, the sensor should be operated at the lowest possible power level. With moving air, liquid or surface temperature sensing, selfheating is not as great a problem since the measured 2 Typical Performance Characteristics Temperature Conversion Op Amp Input Current Power Supply Current TCENTIGRADE e TC TFAHRENHEIT e TF TKELVIN e TK TK e TC a 273.16 5 b 40 TC e (40 a TF) 9 9 b 40 TF e (40 a TC) 5 Output Saturation Voltage Thermal Time Constant in Stirred Oil Bath Thermal Time Constant in Still Air Supply Sensitivity Device Temperature Rise Device Temperature Rise Reference Regulation Turn ‘‘ON’’ Response Amplifier Output Impedance TL/H/5701 – 2 3 Schematic Diagram Typical Applications (Continued) Basic Thermometer for Negative Supply Basic Thermometer for Positive Supply Increasing Output Drive Note: Load current to GND is supplied through RS RS e (Vb b 6.8V) c 103X External Frequency Compensation for Greater Stability when Driving Capacitive Loads RS e (Vb b 6.8V) c 103X Operating With External Zener for Lower Power Dissipation *Depends on Zener current. 4 RS e (V a b 6.8V) c 103X Temperature Controller With Hysteresis *Output goes positive on temperature increase ² Set temperature TL/H/5701 – 3 Typical Applications (Continued) Meter Thermometer With Trimmed Output Thermometer With Meter Output (VZ) 0.01DT ** R1* e IM (VZ b 0.01 TO) Select IQ s R2 e 2V R1 0.01 TO b IQR1 IQ VZ b R1 b R2 R3 e IQ #I Qs Vz DT IM TO IQ 2V R1 e e e e e J Shunt regulator voltage (use 6.85) Meter temperature span (§ K) Meter full scale current (A) Meter zero temperature (§ K) Current through R1, R2, R3 at zero meter current (10 mA to 1.0 mA) (A) *Values shown for: *Selected as for meter thermometer except TO should be 5§ K more than desired and IQ e 100 mA TO e 300§ K, DT e 100§ K, IM e 1.0 mA, IQ e 100 mA ² Calibrates TO **The 0.01 in the above and following equations is in units of V/§ K or V/§ C, and is a result of the basic 0.01V/§ K sensitivity of the transducer Ground Referred Thermometer R1 e R2 e (VZ)(10mV)(DT) VO (VZ b 0.01 TO) RL Ground Referred Centigrade Thermometer 0.01 TO b IQ R1 IQ VZ b R1 b R2 R3 e IQ Vz e Shunt regulator voltage DT e Temperature span (§ K) TO e Temperature for zero output (§ K) VO e Full scale output voltage s 10V IQ e Current through R1, R2, R3 at zero output voltage (typically 100 mA to 1.0 mA) *Set zero R2 (X) e #V J # I R1 J # V 0.01 T J # R1 0.01 T (V 0.01 T ) T (V 0.01 T ) R1 R3 Ð ( Z b 0.01 TL Hb H Two Terminal Temperature to Current Transducer* VZ R3(X) t #T TH b1 L IH b IL TH TL e e e e e a Zb Zb L b L H Zb 0.01 TL J b IL ** H J 1 1 e R4 (VZ b 0.01 TL)(R2) TL TH VZ IL IH 0.01 TH % (R2)(0.01 TL) a R1 # VZ b 0.01 TL b IL R2 1 1 a R2 R3 J b – 1 R2 Temperature for IL ( K) Temperature for IH ( K) Zener voltage (V) Low temperature output current (A) High temperature output current (A) *Values shown for IOUT e 1 mA to 10 mA for 10§ F to 100§ F ² Set temperature TL/H/5701 – 4 **The 0.01 in the above and following equations is in units of V/§ K or V/§ C, and is a result of the basic 0.01V/§ K sensitivity of the transducer 5 Typical Applications (Continued) Over Temperature Detectors With Common Output Trip Point e VZ RS e (V R1 R1 a R2 a b 6.8V) 0.001 A a 6.8V R1 a R2 TL/H/5701 – 5 Two-Wire Remote A.C. Electronic Thermostat (Gas or Oil Furnace Control) TL/H/5701 – 8 *Solenoid or 6 b 15W heater ² Pot will provide about a 50§ F to 90§ F setting range. The trim resistor (100k) is selected to bring 70§ F near the middle of the pot rotation. SCR heating, by proper positioning, can preheat the sensor giving control anticipation as is presently used in many home thermostats. Electronic Thermostat SENSITIVE GATE TRIAC IGT e s 5 mA RCA T2300, 40529 OR SIMILAR *Set temperature ² SCR turns on power to fan or cooler when temperature inTL/H/5701 – 9 creases. 6 Typical Applications (Continued) Three-Wire Electronic Thermostat *Divider is set for a nominal 0§ C b 125§ C range. Wire wound resistors will provide maximum temperature stability. **Almost any TRIAC rated 1 to 35 amperes usable with appropriate load. Differential Thermometer Kelvin Thermometer With Ground Referred Output VS a b 6.8V c 103X RS e 2 # R J (T T )** Output can swing 3V at 50 mA VOUT e 0.01 R1 a R2 2b 1 g 1 g with low output impedance **The 0.01 in the above equation is in units of V/§ K or V/§ C, and is a result of the basic 0.01 V/§ K sensitivity of the transducer Connection Diagrams TO-46 Package Dual-In-Line Package TL/H/5701 – 6 Order Number LM3911N See NS Package N08E 7 TL/H/5701 – 7 Order Number LM3911H-46 See NS Package H04A LM3911 Temperature Controller Physical Dimensions inches (millimeters) Molded Dual-In-Line Package (N) Order Number LM3911N NS Package N08E TO-46 Package (H) Order Number LM3911H-46 NS Package H04A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. 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