LM45CIM3

LM45 SOT-23 Precision Centigrade Temperature Sensors August 2005 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 n n n n n n n n Battery Management FAX Machines Printers 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 01175401 Top View See NS Package Number mf03a Order Number LM45BIM3 LM45BIM3X LM45CIM3 LM45CIM3X Device Top Mark T4B T4B T4C T4C Supplied As 1000 Units on Tape and Reel 3000 Units on Tape and Reel 1000 Units on Tape and Reel 3000 Units on Tape and Reel © 2005 National Semiconductor Corporation DS011754 www.national.com LM45 Typical Applications 01175403 FIGURE 1. Basic Centigrade Temperature Sensor (+2.5˚C to +100˚C) 01175404 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) www.national.com 2 LM45 Absolute Maximum Ratings (Note 1) Supply Voltage Output Voltage Output Current Storage Temperature ESD Susceptibility (Note 3): Human Body Model Machine Model +12V to −0.2V +V S Operating Ratings (Note 1) Specified Temperature Range (Note 4) LM45B, LM45C Operating Temperature Range LM45B, LM45C Supply Voltage Range (+VS) −40˚C to +125˚C +4.0V to +10V T MIN + 0.6V to −1.0V 10 mA to TMAX −20˚C to +100˚C −65˚C to +150˚C 2000V 250V Soldering process must comply with National Semiconductor’s Reflow Temperature Profile specifications. Refer to www.national.com/packaging. (Note 2) 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 J = TMIN to TMAX ; all other limits TA = TJ = +25˚C, unless otherwise noted. Parameter Conditions LM45B Typical Accuracy (Note 6) Nonlinearity (Note 7) Sensor Gain (Average Slope) Load Regulation (Note 8) Line Regulation (Note 8) Quiescent Current (Note 9) Change of Quiescent Current (Note 9) Temperature Coefficient of Quiescent Current Minimum Temperature for Rated Accuracy Long Term Stability (Note 10) In circuit of Figure 1, IL=0 T J=TMAX, for 1000 hours +2.5 +2.5 ˚C (min) ˚C +2.0 +2.0 µA/˚C +4.0V≤+V S≤+10V, +25˚C +4.0V≤+V S≤+10V 4.0V≤+V S≤10V 0≤I L≤ +1 mA +4.0V≤+V S≤+10V T MIN≤TA≤TMAX +9.7 +10.3 +9.7 +10.3 mV/˚C (min) mV/˚C (max) mV/mA (max) mV/V (max) mV/V (max) µA (max) µA (max) µA (max) T A=+25˚C T A=TMAX T A=TMIN T MIN≤TA≤TMAX Limit (Note 5) LM45C Typical Limit (Note 5) Units (Limit) ˚C (max) ˚C (max) ˚C (max) ˚C (max) ± 2.0 ± 3.0 ± 3.0 ± 0.8 ± 3.0 ± 4.0 ± 4.0 ± 0.8 ± 35 ± 0.80 ± 1.2 120 160 2.0 ± 35 ± 0.80 ± 1.2 120 160 2.0 ± 0.12 ± 0.12 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: Reflow temperature profiles are different for lead-free and non-lead-free packages. 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. 3 www.national.com LM45 Typical Performance Characteristics circuit board as shown in Figure 3. Thermal Resistance Junction to Air To generate these curves the LM45 was mounted to a printed Thermal Time Constant 01175424 01175425 Thermal Response in Still Air with Heat Sink (Figure 3) Thermal Response in Stirred Oil Bath with Heat Sink 01175426 01175427 Start-Up Voltage vs Temperature Quiescent Current vs Temperature (In Circuit of Figure 1) 01175428 01175429 www.national.com 4 LM45 Typical Performance Characteristics To generate these curves the LM45 was mounted to a printed circuit board as shown in Figure 3. (Continued) Quiescent Current vs Temperature (In Circuit of Figure 2) Accuracy vs Temperature (Guaranteed) 01175430 01175431 Noise Voltage Supply Voltage vs Supply Current 01175432 01175433 Start-Up Response 01175434 5 www.national.com LM45 Printed Circuit Board 01175423 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 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 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) SOT-23 no heat sink* Still air Moving air 450˚C/W SOT-23 small heat fin** 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 attached as shown in Figure 3. www.national.com 6 LM45 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. 01175414 FIGURE 7. 4-to-20 mA Current Source (0˚C to +100˚C) 01175408 FIGURE 4. LM45 with Decoupling from Capacitive Load 01175409 01175415 FIGURE 5. LM45 with R-C Damper FIGURE 8. Fahrenheit Thermometer 01175416 01175412 FIGURE 9. Centigrade Thermometer (Analog Meter) FIGURE 6. Temperature Sensor, Single Supply, −20˚C to +100˚C 7 www.national.com LM45 Typical Applications (Continued) 01175417 FIGURE 10. Expanded Scale Thermometer (50˚ to 80˚ Fahrenheit, for Example Shown) 01175418 FIGURE 11. Temperature To Digital Converter (Serial Output) (+128˚C Full Scale) 01175419 FIGURE 12. Temperature To Digital Converter (Parallel TRI-STATE ® Outputs for Standard Data Bus to µP Interface) (128˚C Full Scale) www.national.com 8 LM45 Typical Applications (Continued) 01175420 * =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) 01175421 FIGURE 14. LM45 With Voltage-To-Frequency Converter And Isolated Output (2.5˚C to +100˚C; 25 Hz to 1000 Hz) 9 www.national.com LM45 Block Diagram 01175422 www.national.com 10 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 mf03a 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. For the most current product information visit us at www.national.com. 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. BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. Leadfree products are RoHS compliant. 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