LM34 Precision Fahrenheit Temperature Sensors General Description The LM34 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Fahrenheit temperature. The LM34 thus has an advantage over linear temperature sensors calibrated in degrees Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Fahrenheit scaling. The LM34 does not require any external calibration or trimming to provide typical accuracies of ± 1⁄2˚F at room temperature and ± 11⁄2˚F over a full −50 to +300˚F temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM34’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies or with plus and minus supplies. As it draws only 75 µA from its supply, it has very low self-heating, less than 0.2˚F in still air. The LM34 is rated to operate over a −50˚ to +300˚F temperature range, while the LM34C is rated for a −40˚ to +230˚F range (0˚F with improved accuracy). The LM34 series is available packaged in hermetic TO-46 transistor packages, while the LM34C, LM34CA and LM34D are also available in the plastic TO-92 transistor package. The LM34D is also available in an 8-lead surface mount small outline package. The LM34 is a complement to the LM35 (Centigrade) temperature sensor. Features n n n n n n n n n n n Calibrated directly in degrees Fahrenheit Linear +10.0 mV/˚F scale factor 1.0˚F accuracy guaranteed (at +77˚F) Rated for full −50˚ to +300˚F range Suitable for remote applications Low cost due to wafer-level trimming Operates from 5 to 30 volts Less than 90 µA current drain Low self-heating, 0.18˚F in still air Nonlinearity only ± 0.5˚F typical Low-impedance output, 0.4Ω for 1 mA load Connection Diagrams TO-46 Metal Can Package (Note 1) TO-92 Plastic Package DS006685-1 SO-8 Small Outline Molded Package DS006685-2 Order Numbers LM34H, LM34AH, LM34CH, LM34CAH or LM34DH See NS Package Number H03H Order Number LM34CZ, LM34CAZ or LM34DZ See NS Package Number Z03A DS006685-20 N.C. = No Connection Top View Order Number LM34DM See NS Package Number M08A Note 1: Case is connected to negative pin (GND). © 2000 National Semiconductor Corporation DS006685 www.national.com LM34 Precision Fahrenheit Temperature Sensors November 2000 LM34 Typical Applications DS006685-3 FIGURE 1. Basic Fahrenheit Temperature Sensor (+5˚ to +300˚F) DS006685-4 FIGURE 2. Full-Range Fahrenheit Temperature Sensor www.national.com 2 TO-46 Package (Soldering, 10 seconds) TO-92 Package (Soldering, 10 seconds) SO Package (Note 13) Vapor Phase (60 seconds) Infrared (15 seconds) Specified Operating Temp. Range (Note 3) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Output Voltage Output Current Storage Temperature, TO-46 Package TO-92 Package SO-8 Package ESD Susceptibility (Note 12) Lead Temp. LM34 Absolute Maximum Ratings (Note 11) +35V to −0.2V +6V to −1.0V 10 mA −76˚F to +356˚F −76˚F to +300˚F −65˚C to +150˚C 800V +300˚C +260˚C 215˚C 220˚C TMIN to TMAX −50˚F to +300˚F −40˚F to +230˚F +32˚F to +212˚F LM34, LM34A LM34C, LM34CA LM34D DC Electrical Characteristics (Notes 2, 7) LM34A Parameter Conditions Typical Nonlinearity (Note 9) TMIN ≤ TA ≤ TMAX ± 0.4 ± 0.6 ± 0.8 ± 0.8 ± 0.35 Sensor Gain TMIN ≤ TA ≤ TMAX +10.0 Accuracy (Note 8) TA = +77˚F TA = 0˚F TA = TMAX TA = TMIN (Average Slope) LM34CA Tested Design Limit Limit (Note 5) (Note 6) ± 1.0 +9.9, ± 2.0 ± 2.0 ± 0.7 Typical ± 0.4 ± 0.6 ± 0.8 ± 0.8 ± 0.30 Tested Design Units Limit Limit (Max) (Note 5) (Note 6) ± 1.0 ± 2.0 +10.0 +10.1 Load Regulation TA = +77˚F (Note 4) TMIN ≤ TA ≤ TMAX ± 0.4 ± 0.5 ± 1.0 ± 0.01 ± 0.02 ± 0.05 90 ˚F ± 2.0 ± 0.4 ± 0.5 ± 1.0 ± 3.0 ± 0.05 ± 0.1 ± 0.01 ± 0.02 75 90 ˚F ˚F ± 3.0 ± 0.6 ˚F +9.9, mV/˚F, min +10.1 mV/˚F, max ˚F mV/mA ± 3.0 mV/mA 0 ≤ IL ≤ 1 mA Line Regulation TA = +77˚F (Note 4) 5V ≤ VS ≤ 30V Quiescent Current VS = +5V, +77˚F 75 (Note 10) VS = +5V 131 VS = +30V, +77˚F 76 VS = +30V 132 Change of Quiescent 4V ≤ VS ≤ 30V, +77˚F +0.5 Current (Note 4) 5V ≤ VS ≤ 30V Temperature Coefficient 160 116 163 117 92 76 2.0 0.5 mV/V ± 0.1 mV/V 139 µA 142 µA µA 92 µA 2.0 µA +1.0 3.0 1.0 3.0 µA +0.30 +0.5 +0.30 +0.5 µA/˚F +3.0 +5.0 +3.0 +5.0 ˚F of Quiescent Current Minimum Temperature In circuit of Figure 1, for Rated Accuracy IL = 0 Long-Term Stability Tj = TMAX for 1000 hours ± 0.16 ± 0.16 ˚F Note 2: Unless otherwise noted, these specifications apply: −50˚F ≤ Tj ≤ + 300˚F for the LM34 and LM34A; −40˚F ≤ Tj ≤ +230˚F for the LM34C and LM34CA; and +32˚F ≤ Tj ≤ + 212˚F for the LM34D. VS = +5 Vdc and ILOAD = 50 µA in the circuit of Figure 2; +6 Vdc for LM34 and LM34A for 230˚F ≤ Tj ≤ 300˚F. These specifications also apply from +5˚F to TMAX in the circuit of Figure 1. Note 3: Thermal resistance of the TO-46 package is 720˚F/W junction to ambient and 43˚F/W junction to case. Thermal resistance of the TO-92 package is 324˚F/W junction to ambient. Thermal resistance of the small outline molded package is 400˚F/W junction to ambient. For additional thermal resistance information see table in the Typical Applications section. Note 4: Regulation is measured at constant junction temperature using pulse testing with a low duty cycle. Changes in output due to heating effects can be computed by multiplying the internal dissipation by the thermal resistance. Note 5: Tested limits are guaranteed and 100% tested in production. Note 6: Design limits are guaranteed (but not 100% production tested) over the indicated temperature and supply voltage ranges. These limits are not used to calculate outgoing quality levels. Note 7: Specification in BOLDFACE TYPE apply over the full rated temperature range. 3 www.national.com LM34 DC Electrical Characteristics (Notes 2, 7) (Continued) Note 8: Accuracy is defined as the error between the output voltage and 10 mV/˚F times the device’s case temperature at specified conditions of voltage, current, and temperature (expressed in ˚F). Note 9: Nonlinearity is defined as the deviation of the output-voltage-versus-temperature curve from the best-fit straight line over the device’s rated temperature range. Note 10: Quiescent current is defined in the circuit of Figure 1. Note 11: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions (Note 2). Note 12: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Note 13: See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in a current National Semiconductor Linear Data Book for other methods of soldering surface mount devices. DC Electrical Characteristics (Notes 2, 7) LM34 Parameter Conditions Tested Typical Accuracy, LM34, LM34C (Note 8) TA = +77˚F TA = 0˚F TA = TMAX TA = TMIN Accuracy, LM34D (Note 8) ± 0.8 ± 1.0 ± 1.6 ± 1.6 LM34C, LM34D Design Limit Limit (Note 5) (Note 6) ± 2.0 ± 3.0 ± 3.0 TA = +77˚F TA = TMAX TA = TMIN Nonlinearity (Note 9) TMIN ≤ TA ≤ TMAX ± 0.6 Sensor Gain TMIN ≤ TA ≤ TMAX +10.0 (Average Slope) ± 1.0 +9.8, Tested Typical ± 0.8 ± 1.0 ± 1.6 ± 1.6 ± 1.2 ± 1.8 ± 1.8 ± 0.4 Design Units Limit Limit (Max) (Note 5) (Note 6) ± 2.0 ± 3.0 +10.0 TA = +77˚F (Note 4) TMIN ≤ TA ≤ +150˚F Line Regulation TA = +77˚F (Note 4) 5V ≤ VS ≤ 30V ± 0.4 ± 0.5 ± 2.5 ± 0.01 ± 0.02 ± 0.1 100 ± 0.4 ± 0.5 ± 2.5 ± 6.0 ± 0.01 ± 0.02 ± 0.1 ± 0.2 75 100 176 116 ˚F ˚F ˚F ˚F ± 4.0 ± 4.0 ± 1.0 +10.2 Load Regulation ˚F ± 3.0 ± 3.0 ± 4.0 ˚F ˚F ˚F +9.8, mV/˚F, min +10.2 mV/˚F, max mV/mA ± 6.0 mV/mA ± 0.2 mV/V 154 µA 0 ≤ IL ≤ 1 mA Quiescent Current VS = +5V, +77˚F 75 (Note 10) VS = +5V 131 VS = +30V, +77˚F 76 103 76 VS = +30V 132 Change of Quiescent 4V ≤ VS ≤ 30V, +77˚F +0.5 Current (Note 4) 5V ≤ VS ≤ 30V +1.0 5.0 +0.30 +3.0 Temperature Coefficient 181 mV/V µA 103 159 µA 1.0 5.0 µA +0.7 +0.30 +0.7 µA/˚F +5.0 +3.0 +5.0 ˚F 3.0 117 µA 0.5 3.0 µA of Quiescent Current Minimum Temperature In circuit of Figure 1, for Rated Accuracy IL = 0 Long-Term Stability Tj = TMAX for 1000 hours www.national.com ± 0.16 ± 0.16 4 ˚F LM34 Typical Performance Characteristics Thermal Resistance Junction to Air Thermal Response in Still Air Thermal Time Constant DS006685-23 DS006685-22 Thermal Response in Stirred Oil Bath DS006685-24 Minimum Supply Voltage vs. Temperature DS006685-25 Quiescent Current vs. Temperature (In Circuit of Figure 1) DS006685-26 DS006685-27 Quiescent Current vs. Temperature (In Circuit of Figure 2; −VS = −5V, R1 = 100k) Accuracy vs. Temperature (Guaranteed) Accuracy vs. Temperature (Guaranteed) DS006685-29 DS006685-28 5 DS006685-30 www.national.com LM34 Typical Performance Characteristics (Continued) Noise Voltage Start-Up Response DS006685-31 DS006685-32 These devices are sometimes soldered to a small, light-weight heat fin to decrease the thermal time constant and speed up the response in slowly-moving air. On the other hand, a small thermal mass may be added to the sensor to give the steadiest reading despite small deviations in the air temperature. Typical Applications The LM34 can be applied easily in the same way as other integrated-circuit temperature sensors. It can be glued or cemented to a surface and its temperature will be within about 0.02˚F of the surface temperature. This presumes that the ambient air temperature is almost the same as the surface temperature; if the air temperature were much higher or lower than the surface temperature, the actual temperature of the LM34 die would be at an intermediate temperature between the surface temperature and the air temperature. This is expecially true for the TO-92 plastic package, where the copper leads are the principal thermal path to carry heat into the device, so its temperature might be closer to the air temperature than to the surface temperature. To minimize this problem, be sure that the wiring to the LM34, as it leaves the device, is held at the same temperature as the surface of interest. The easiest way to do this is to cover up these wires with a bead of epoxy which will insure that the leads and wires are all at the same temperature as the surface, and that the LM34 die’s temperature will not be affected by the air temperature. The TO-46 metal package can also be soldered to a metal surface or pipe without damage. Of course in that case, the V− terminal of the circuit will be grounded to that metal. Alternatively, the LM34 can be mounted inside a sealed-end metal tube, and can then be dipped into a bath or screwed into a threaded hole in a tank. As with any IC, the LM34 and accompanying wiring and circuits must be kept insulated and dry, to avoid leakage and corrosion. This is especially true if the circuit may operate at cold temperatures where condensation can occur. Printed-circuit coatings and varnishes such as Humiseal and epoxy paints or dips are often used to insure that moisture cannot corrode the LM34 or its connections. Capacitive Loads Like most micropower circuits, the LM34 has a limited ability to drive heavy capacitive loads. The LM34 by itself is able to drive 50 pF without special precautions. If heavier loads are anticipated, it is easy to isolate or decouple the load with a resistor; see Figure 3. Or you can improve the tolerance of capacitance with a series R-C damper from output to ground; see Figure 4. When the LM34 is applied with a 499Ω load resistor (as shown), it is relatively immune to wiring capacitance because the capacitance forms a bypass from ground to input, not on the output. However, as with any linear circuit connected to wires in a hostile environment, its performance can be affected adversely by intense electromagnetic sources such as relays, radio transmitters, motors with arcing brushes, SCR’s transients, etc., as its wiring can act as a receiving antenna and its internal junctions can act as rectifiers. For best results in such cases, a bypass capacitor from VIN to ground and a series R-C damper such as 75Ω in series with 0.2 or 1 µF from output to ground are often useful. These are shown in the following circuits. DS006685-6 www.national.com 6 LM34 Typical Applications DS006685-7 FIGURE 3. LM34 with Decoupling from Capacitive Load DS006685-8 FIGURE 4. LM34 with R-C Damper Temperature Rise of LM34 Due to Self-Heating (Thermal Resistance) Conditions TO-46, TO-46, TO-92, TO-92, SO-8 SO-8 No Heat Sink Small Heat Fin (Note 14) No Heat Sink Small Heat Fin (Note 15) No Heat Sink Small Heat Fin (Note 15) Still air 720˚F/W 180˚F/W 324˚F/W 252˚F/W 400˚F/W 200˚F/W Moving air 180˚F/W 72˚F/W 162˚F/W 126˚F/W 190˚F/W 160˚F/W Still oil 180˚F/W 72˚F/W 162˚F/W 126˚F/W Stirred oil 90˚F/W 54˚F/W 81˚F/W 72˚F/W (Clamped to metal, (43˚F/W) (95˚F/W) infinite heat sink) Note 14: Wakefield type 201 or 1" disc of 0.020" sheet brass, soldered to case, or similar. Note 15: TO-92 and SO-8 packages glued and leads soldered to 1" square of 1/16" printed circuit board with 2 oz copper foil, or similar. Two-Wire Remote Temperature Sensor (Grounded Sensor) Two-Wire Remote Temperature Sensor (Output Referred to Ground) DS006685-9 DS006685-10 VOUT = 10mV/˚F (TA+3˚F) FROM +3˚F TO + 100˚F 7 www.national.com LM34 Typical Applications (Continued) 4-to-20 mA Current Source (0 to +100˚F) Fahrenheit Thermometer (Analog Meter) DS006685-12 DS006685-11 Expanded Scale Thermometer (50˚ to 80˚ Fahrenheit, for Example Shown) Temperature-to-Digital Converter (Serial Output, +128˚F Full Scale) DS006685-14 DS006685-13 LM34 with Voltage-to-Frequency Converter and Isolated Output (3˚F to + 300˚F; 30 Hz to 3000 Hz) DS006685-15 www.national.com 8 LM34 Typical Applications (Continued) Bar-Graph Temperature Display (Dot Mode) DS006685-16 * = 1% or 2% film resistor — Trim RB for VB = 3.525V — Trim RC for VC = 2.725V — Trim RA for VA = 0.085V + 40 mV/˚F x TAMBIENT — Example, VA = 3.285V at 80˚F Temperature-to-Digital Converter (Parallel TRI-STATE ® Outputs for Standard Data Bus to µP Interface, 128 ˚F Full Scale) DS006685-17 9 www.national.com LM34 Typical Applications (Continued) Temperature Controller DS006685-18 Block Diagram DS006685-19 www.national.com 10 LM34 Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM34H, LM34AH, LM34CH, LM34CAH or LM34DH NS Package H03H Order Number LM34DM NS Package Number M08A 11 www.national.com LM34 Precision Fahrenheit Temperature Sensors Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Order Number LM34CZ, LM34CAZ or LM34DZ NS Package Z03A 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 AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. 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