LM45B/LM45C SOT-23 Precision Centigrade Temperature Sensors Y General Description Y 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 g 2§ C at room temperature and g 3§ C over a full b 20 to a 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 mA 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 b20§ to a 100§ C temperature range. Y Y Y Y Features Y Y Y Y Y Y Y Applications Y Y Y Y Y Battery Management FAX Machines Printers Portable Medical Instruments HVAC Power Supply Modules Disk Drives Computers Automotive Y Y Calibrated directly in § Celsius (Centigrade) Linear a 10.0 mV/§ C scale factor g 3§ C accuracy guaranteed Rated for full b20§ to a 100§ C range Suitable for remote applications Low cost due to wafer-level trimming Operates from 4.0V to 10V Less than 120 mA current drain Low self-heating, 0.20§ C in still air Nonlinearity only g 0.8§ C max over temp Low impedance output, 20X for 1 mA load Connection Diagram SOT-23 SOT-23 Device Marking Supplied As LM45BIM3 T4B 250 Units on Tape and Reel LM45BIM3X T4B 3000 Units on Tape and Reel LM45CIM3 T4C 250 Units on Tape and Reel LM45CIM3X T4C 3000 Units on Tape and Reel Order Number TL/H/11754 – 1 Top View See NS Package Number M03B (JEDEC Registration TO-236AB) Typical Applications TL/H/11754 – 3 FIGURE 1. Basic Centigrade Temperature Sensor ( a 2.5§ C to a 100§ C) Choose R1 e b VS/50 mA TL/H/11754 – 4 VOUT e (10 mV/§ C c Temp § C) VOUT e a 1,000 mV at a 100§ C e a 250 mV at a 25§ C e b 200 mV at b 20§ C FIGURE 2. Full-Range Centigrade Temperature Sensor (b20§ C to a 100§ C) C1995 National Semiconductor Corporation TL/H/11754 RRD-B30M75/Printed in U. S. A. LM45B/LM45C SOT-23 Precision Centigrade Temperature Sensors May 1995 Absolute Maximum Ratings (Note 1) Supply Voltage Output Voltage Output Current Storage Temperature Lead Temperature SOT Package (Note 2): Vapor Phase (60 seconds) Infrared (15 seconds) a 12V to b 0.2V a VS a 0.6V to b 1.0V ESD Susceptibility (Note 3): Human Body Model Machine Model 10 mA b 65§ C to a 150§ C 2000V TBD Operating Ratings (Note 1) Specified Temperature Range (Note 4) LM45B, LM45C Operating Temperature Range LM45B, LM45C 215§ C 220§ C TMIN to TMAX b 20§ C to a 100§ C b 40§ C to a 125§ C Supply Voltage Range ( a VS) a 4.0V to a 10V Electrical Characteristics Unless otherwise noted, these specifications apply for a VS e a 5Vdc and ILOAD e a 50 mA, in the circuit of Figure 2 . These specifications also apply from a 2.5§ C to TMAX in the circuit of Figure 1 for a VS e a 5Vdc. Boldface limits apply for TA e TJ e TMIN to TMAX; all other limits TA e TJ e a 25§ C, unless otherwise noted. LM45B Parameter Conditions Typical LM45C Limit (Note 5) Typical Limit (Note 5) Units (Limit) Accuracy (Note 6) TA e a 25§ C TA e TMAX TA e TMIN g 2.0 g 3.0 g 3.0 g 3.0 g 4.0 g 4.0 § C (max) § C (max) § C (max) Nonlinearity (Note 7) TMINsTAsTMAX g 0.8 g 0.8 § C (max) Sensor Gain (Average Slope) TMINsTAsTMAX a 9.7 a 10.3 a 9.7 a 10.3 mV/§ C (min) mV/§ C (max) Load Regulation (Note 8) 0sILs a 1 mA g 35 g 35 mV/mA (max) Line Regulation (Note 8) a 4.0V s a VS s a 10V g 0.80 g 1.2 g 0.80 g 1.2 mV/V (max) mV/V (max) Quiescent Current (Note 9) a 4.0V s a VS s a 10V, a 25§ C a 4.0V s a VS s a 10V 120 160 120 160 mA (max) mA (max) Change of Quiescent Current (Note 8) 4.0Vs a VSs10V 2.0 2.0 mA (max) Temperature Coefficient of Quiescent Current a 2.0 Minimum Temperature for Rated Accuracy In circuit of Figure 1 , IL e 0 Long Term Stability (Note 10) TJ e TMAX, for 1000 hours a 2.0 a 2.5 g 0.12 mA/§ C a 2.5 g 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 kX 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. 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 Time Constant Thermal Response in Still Air with Heat Sink (Figure 3 ) Thermal Response in Stirred Oil Bath with Heat Sink Start-Up Voltage vs Temperature Quiescent Current vs Temperature (In Circuit of Figure 1 ) Quiescent Current vs Temperature (In Circuit of Figure 2 ) Accuracy vs Temperature (Guaranteed) Noise Voltage Supply Voltage vs Supply Current Start-Up Response TL/H/11754 – 23 TL/H/11754 – 5 3 FIGURE 3. Printed Circuit Board Used for Heat Sink to Generate All Curves. (/2× Square Printed Circuit Board with 2 oz. Foil or Similar Applications 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 as Humiseal and epoxy paints or dips are often used to insure that moisture cannot corrode the LM45 or its connections. 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 Temperature Rise of LM45 Due to Self-Heating (Thermal Resistance) SOT-23** SOT-23 no heat sink small heat fin* Still air 450§ C/W 260§ C/W Moving air 180§ C/W * Heat sink used is (/2× square printed circuit board with 2 oz. foil with part attached as shown in Figure 3 . ** Part soldered to 30 gauge wire. 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 75X in series with 0.2 or 1 mF from output to ground, as shown in Figure 5 , are often useful. TL/H/11754 – 9 FIGURE 5. LM45 with R-C Damper TL/H/11754 – 12 FIGURE 6. Temperature Sensor, Single Supply, b20§ C to a 100§ C TL/H/11754–8 FIGURE 4. LM45 with Decoupling from Capacitive Load 4 Typical Applications (Continued) TL/H/11754 – 14 FIGURE 7. 4-to-20 mA Current Source (0§ C to a 100§ C) TL/H/11754 – 15 FIGURE 8. Fahrenheit Thermometer TL/H/11754 – 16 FIGURE 9. Centigrade Thermometer (Analog Meter) TL/H/11754 – 17 FIGURE 10. Expanded Scale Thermometer (50§ to 80§ Fahrenheit, for Example Shown) TL/H/11754 – 18 FIGURE 11. Temperature To Digital Converter (Serial Output) ( a 128§ C Full Scale) 5 Typical Applications (Continued) TL/H/11754 – 19 FIGURE 12. Temperature To Digital Converter (Parallel TRI-STATEÉ Outputs for Standard Data Bus to mP Interface) (128§ C Full Scale) TL/H/11754 – 20 * e 1% or 2% film resistor -Trim RB for VB e 3.075V -Trim RC for VC e 1.955V -Trim RA for VA e 0.075V a 100mV/§ C c Tambient -Example, VA e 2.275V at 22§ C FIGURE 13. Bar-Graph Temperature Display (Dot Mode) 6 Typical Applications (Continued) TL/H/11754 – 21 FIGURE 14. LM45 With Voltage-To-Frequency Converter And Isolated Output (2.5§ C to a 100§ C; 25 Hz to 1000 Hz) Block Diagram TL/H/11754 – 22 7 LM45B/LM45C SOT-23 Precision Centigrade Temperature Sensors Physical Dimensions inches (millimeters) SOT-23 Molded Small Outline Transistor Package (M3) Order Number LM45BIM3, LM45BIM3X, LM45CIM3 or LM45CIM3X NS Package Number M03B (JEDEC Registration TO-236AB) 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. 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 2900 Semiconductor Drive P.O. Box 58090 Santa Clara, CA 95052-8090 Tel: 1(800) 272-9959 TWX: (910) 339-9240 National Semiconductor GmbH Livry-Gargan-Str. 10 D-82256 F4urstenfeldbruck Germany Tel: (81-41) 35-0 Telex: 527649 Fax: (81-41) 35-1 National Semiconductor Japan Ltd. Sumitomo Chemical Engineering Center Bldg. 7F 1-7-1, Nakase, Mihama-Ku Chiba-City, Ciba Prefecture 261 Tel: (043) 299-2300 Fax: (043) 299-2500 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 Hong Kong Ltd. 13th Floor, Straight Block, Ocean Centre, 5 Canton Rd. Tsimshatsui, Kowloon Hong Kong Tel: (852) 2737-1600 Fax: (852) 2736-9960 National Semiconductores Do Brazil Ltda. Rue Deputado Lacorda Franco 120-3A Sao Paulo-SP Brazil 05418-000 Tel: (55-11) 212-5066 Telex: 391-1131931 NSBR BR Fax: (55-11) 212-1181 National Semiconductor (Australia) Pty, Ltd. Building 16 Business Park Drive Monash Business Park Nottinghill, Melbourne Victoria 3168 Australia Tel: (3) 558-9999 Fax: (3) 558-9998 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.