LM45 SOT-23 Precision Centigrade Temperature Sensors General Description The LM45 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM45 does not require any external calibration or trimming to provide accuracies of ± 2˚C at room temperature and ± 3˚C over a full −20 to +100˚C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM45’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with a single power supply, or with plus and minus supplies. As it draws only 120 µA from its supply, it has very low self-heating, less than 0.2˚C in still air. The LM45 is rated to operate over a −20˚ to +100˚C temperature range. Applications n Battery Management n FAX Machines n Printers n n n n n n Portable Medical Instruments HVAC Power Supply Modules Disk Drives Computers Automotive Features n n n n n n n n n n n Calibrated directly in ˚ Celsius (Centigrade) Linear + 10.0 mV/˚C scale factor ± 3˚C accuracy guaranteed Rated for full −20˚ to +100˚C range Suitable for remote applications Low cost due to wafer-level trimming Operates from 4.0V to 10V Less than 120 µA current drain Low self-heating, 0.20˚C in still air Nonlinearity only ± 0.8˚C max over temp Low impedance output, 20Ω for 1 mA load Connection Diagram SOT-23 SOT-23 Order Device Number Marking Supplied As T4B 1000 Units on Tape and Reel LM45BIM3 LM45BIM3X T4B 3000 Units on Tape and Reel LM45CIM3 T4C 1000 Units on Tape and Reel LM45CIM3X T4C 3000 Units on Tape and Reel DS011754-1 Top View See NS Package Number MA03B Typical Applications DS011754-3 FIGURE 1. Basic Centigrade Temperature Sensor (+2.5˚C to +100˚C) DS011754-4 Choose R1 = −VS/50 µA VOUT = (10 mV/˚C x Temp ˚C) VOUT = +1,000 mV at +100˚C = +250 mV at +25˚C = −200 mV at −20˚C FIGURE 2. Full-Range Centigrade Temperature Sensor (−20˚C to +100˚C) © 1999 National Semiconductor Corporation DS011754 www.national.com LM45 SOT-23 Precision Centigrade Temperature Sensors July 1999 Absolute Maximum Ratings (Note 1) Operating Ratings (Note 1) Supply Voltage Output Voltage Specified Temperature Range (Note 4) LM45B, LM45C Operating Temperature Range LM45B, LM45C Supply Voltage Range (+VS) +12V to −0.2V +V S + 0.6V to −1.0V 10 mA −65˚C to +150˚C Output Current Storage Temperature Lead Temperature: SOT Package (Note 2): Vapor Phase (60 seconds) Infrared (15 seconds) ESD Susceptibility (Note 3): Human Body Model Machine Model T MIN to TMAX −20˚C to +100˚C −40˚C to +125˚C +4.0V to +10V 215˚C 220˚C 2000V 250V Electrical Characteristics Unless otherwise noted, these specifications apply for +VS = +5Vdc and ILOAD = +50 µA, in the circuit of Figure 2. These specifications also apply from +2.5˚C to TMAX in the circuit of Figure 1 for +VS = +5Vdc. Boldface limits apply for TA = T TMIN to TMAX ; all other limits TA = TJ = +25˚C, unless otherwise noted. Parameter Conditions LM45B Typical Accuracy (Note 6) T A = +25˚C T A = TMAX T A = TMIN Nonlinearity T MIN≤TA≤TMAX LM45C Limit Typical Limit (Note 5) (Note 5) ± 2.0 ± 3.0 ± 3.0 ± 0.8 ± 3.0 ± 4.0 ± 4.0 ± 0.8 J = Units (Limit) ˚C (max) ˚C (max) ˚C (max) ˚C (max) (Note 7) Sensor Gain T MIN≤TA≤TMAX (Average Slope) Load Regulation (Note 8) 0≤I L≤ +1 mA Line Regulation +4.0V≤+V S≤+10V (Note 8) +9.7 +9.7 mV/˚C (min) +10.3 +10.3 mV/˚C (max) ± 35 ± 35 mV/mA (max) ± 0.80 ± 1.2 ± 0.80 ± 1.2 mV/V (max) µA (max) mV/V (max) Quiescent Current +4.0V≤+V S≤+10V, +25˚C 120 120 (Note 9) +4.0V≤+V S≤+10V 160 160 µA (max) Change of Quiescent 4.0V≤+V S≤10V 2.0 2.0 µA (max) Current (Note 9) Temperature Coefficient +2.0 +2.0 µA/˚C of Quiescent Current Minimum Temperature In circuit of for Rated Accuracy Figure 1, IL = 0 T J = TMAX, for 1000 hours Long Term Stability (Note 10) +2.5 ± 0.12 +2.5 ± 0.12 ˚C (min) ˚C Note 1: 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: 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. Note 3: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin. Note 4: Thermal resistance of the SOT-23 package is 260˚C/W, junction to ambient when attached to a printed circuit board with 2 oz. foil as shown in Figure 3. Note 5: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 6: Accuracy is defined as the error between the output voltage and 10 mv/˚C times the device’s case temperature, at specified conditions of voltage, current, and temperature (expressed in ˚C). Note 7: 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 8: 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 9: Quiescent current is measured using the circuit of Figure 1. Note 10: For best long-term stability, any precision circuit will give best results if the unit is aged at a warm temperature, and/or temperature cycled for at least 46 hours before long-term life test begins. This is especially true when a small (Surface-Mount) part is wave-soldered; allow time for stress relaxation to occur. www.national.com 2 Typical Performance Characteristics To generate these curves the LM45 was mounted to a printed circuit board as shown in Figure 3. Thermal Resistance Junction to Air Thermal Response in Still Air with Heat Sink (Figure 3) Thermal Time Constant DS011754-24 Thermal Response in Stirred Oil Bath with Heat Sink DS011754-25 DS011754-26 Quiescent Current vs Temperature (In Circuit of Figure 1) Start-Up Voltage vs Temperature DS011754-27 DS011754-28 Quiescent Current vs Temperature (In Circuit of Figure 2) Accuracy vs Temperature (Guaranteed) DS011754-30 DS011754-29 Noise Voltage DS011754-31 DS011754-32 3 www.national.com Typical Performance Characteristics To generate these curves the LM45 was mounted to a printed circuit board as shown in Figure 3. (Continued) Supply Voltage vs Supply Current Start-Up Response DS011754-34 DS011754-33 DS011754-23 FIGURE 3. Printed Circuit Board Used for Heat Sink to Generate All Curves. 1⁄2" Square Printed Circuit Board with 2 oz. Foil or Similar as Humiseal and epoxy paints or dips are often used to insure that moisture cannot corrode the LM45 or its connections. Temperature Rise of LM45 Due to Self-Heating (Thermal Resistance) Applications The LM45 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 0.2˚C 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 LM45 die would be at an intermediate temperature between the surface temperature and the air temperature. To ensure good thermal conductivity the backside of the LM45 die is directly attached to the GND pin. The lands and traces to the LM45 will, of course, be part of the printed circuit board, which is the object whose temperature is being measured. These printed circuit board lands and traces will not cause the LM45s temperature to deviate from the desired temperature. Alternatively, the LM45 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 LM45 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 www.national.com SOT-23 SOT-23 no heat sink* small heat fin** Still air Moving air 450˚C/W 260˚C/W 180˚C/W * Part soldered to 30 gauge wire. ** Heat sink used is 1⁄2” square printed circuit board with 2 oz. foil with part at- tached as shown in Figure 3. 4 Typical Applications CAPACITIVE LOADS Like most micropower circuits, the LM45 has a limited ability to drive heavy capacitive loads. The LM45 by itself is able to drive 500 pF without special precautions. If heavier loads are anticipated, it is easy to isolate or decouple the load with a resistor; see Figure 4. Or you can improve the tolerance of capacitance with a series R-C damper from output to ground; see Figure 5. Any linear circuit connected to wires in a hostile environment can have its performance affected adversely by intense electromagnetic sources such as relays, radio transmitters, motors with arcing brushes, SCR 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, as shown in Figure 5, are often useful. DS011754-14 FIGURE 7. 4-to-20 mA Current Source (0˚C to +100˚C) DS011754-8 FIGURE 4. LM45 with Decoupling from Capacitive Load DS011754-9 FIGURE 5. LM45 with R-C Damper DS011754-15 FIGURE 8. Fahrenheit Thermometer DS011754-12 FIGURE 6. Temperature Sensor, Single Supply, −20˚C to +100˚C DS011754-16 FIGURE 9. Centigrade Thermometer (Analog Meter) 5 www.national.com Typical Applications (Continued) DS011754-17 FIGURE 10. Expanded Scale Thermometer (50˚ to 80˚ Fahrenheit, for Example Shown) DS011754-18 FIGURE 11. Temperature To Digital Converter (Serial Output) (+128˚C Full Scale) DS011754-19 FIGURE 12. Temperature To Digital Converter (Parallel TRI-STATE ® Outputs for Standard Data Bus to µP Interface) (128˚C Full Scale) www.national.com 6 Typical Applications (Continued) DS011754-20 * = 1% or 2% film resistor -Trim RB for VB = 3.075V -Trim RC for VC = 1.955V -Trim RA for VA = 0.075V + 100mV/˚C x Tambient -Example, VA = 2.275V at 22˚C FIGURE 13. Bar-Graph Temperature Display (Dot Mode) DS011754-21 FIGURE 14. LM45 With Voltage-To-Frequency Converter And Isolated Output (2.5˚C to +100˚C; 25 Hz to 1000 Hz) 7 www.national.com Block Diagram DS011754-22 www.national.com 8 LM45 SOT-23 Precision Centigrade Temperature Sensors Physical Dimensions inches (millimeters) unless otherwise noted SOT-23 Molded Small Outline Transistor Package (M3) Order Number LM45BIM3, LM45BIM3X, LM45CIM3 or LM45CIM3X NS Package Number MA03B 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. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.