LM50B/LM50C SOT-23 Single-Supply Centigrade Temperature Sensor Y General Description Y The LM50 is a precision integrated-circuit temperature sensor that can sense a b40§ C to a 125§ C temperature range using a single positive supply. The LM50’s output voltage is linearly proportional to Celsius (Centigrade) temperature ( a 10 mV/§ C) and has a DC offset of a 500 mV. The offset allows reading negative temperatures without the need for a negative supply. The ideal output voltage of the LM50 ranges from a 100 mV to a 1.75V for a b40§ C to a 125§ C temperature range. The LM50 does not require any external calibration or trimming to provide accuracies of g 3§ C at room temperature and g 4§ C over the full b40§ C to a 125§ C temperature range. Trimming and calibration of the LM50 at the wafer level assure low cost and high accuracy. The LM50’s linear output, a 500 mV offset, and factory calibration simplify circuitry required in a single supply environment where reading negative temperatures is required. Because the LM50’s quiescent current is less than 130 mA, self-heating is limited to a very low 0.2§ C in still air. Y Y Y Y Y Features Y Y Y Y Y Y Y Y Y Y Applications Y Y Battery Management Automotive FAX Machines Printers Portable Medical Instruments HVAC Power Supply Modules Calibrated directly in § Celsius (Centigrade) Linear a 10.0 mV/§ C scale factor g 2§ C accuracy guaranteed at a 25§ C Specified for full b40§ to a 125§ C range Suitable for remote applications Low cost due to wafer-level trimming Operates from 4.5V to 10V Less than 130 mA current drain Low self-heating, less than 0.2§ C in still air Nonlinearity less than 0.8§ C over temp Computers Disk Drives Connection Diagram SOT-23 Order Number TL/H/12030–1 Top View SOT-23 Device Marking Supplied As LM50BIM3 T5B 250 Units on Tape and Reel LM50CIM3 T5C 250 Units on Tape and Reel LM50BIM3X T5B 3000 Units on Tape and Reel LM50CIM3X T5C 3000 Units on Tape and Reel See NS Package Number M03B (JEDEC Registration TO-236AB) Typical Application TL/H/12030 – 3 FIGURE 1. Full-Range Centigrade Temperature Sensor (b40§ C to a 125§ C) C1996 National Semiconductor Corporation TL/H/12030 RRD-B30M76/Printed in U. S. A. http://www.national.com LM50B/LM50C SOT-23 Single-Supply Centigrade Temperature Sensor June 1996 Absolute Maximum Ratings (Note 1) a 12V to b 0.2V Supply Voltage Output Voltage ( a VS a 0.6V) to b1.0V Output Current 10 mA b 65§ C to a 150§ C Storage Temperature Lead Temperature SOT Package (Note 2): Vapor Phase (60 seconds) 215§ C Infrared (15 seconds) 220§ C TJMAX, Maximum Junction Temperature 150§ C ESD Susceptibility (Note 3): Human Body Model Machine Model 2000V 200V Operating Ratings (Note 1) TMIN to TMAX Specified Temperature Range: LM50C LM50B b 40§ C to a 125§ C b 25§ C to a 100§ C b 40§ C to a 150§ C Operating Temperature Range iJA (Note 4) Supply Voltage Range ( a VS) 450§ C/W a 4.5V to a 10V Electrical Characteristics Unless otherwise noted, these specifications apply for VS e a 5 VDC and ILOAD e a 0.5 mA, in the circuit of Figure 1. Boldface limits apply for the specified TA e TJ e TMIN to TMAX; all other limits TA e TJ e a 25§ C, unless otherwise noted. LM50B Parameter Accuracy (Note 6) Conditions Typical TA e a 25§ C TA e TMAX TA e TMIN Nonlinearity (Note 7) Sensor Gain (Average Slope) Output Resistance 2000 Line Regulation (Note 8) a 4.5V s VS s a 10V Quiescent Current (Note 9) Change of Quiescent Current (Note 8) Limit (Note 5) Typical Limit (Note 5) g 2.0 g 3.0 g 3.0 g 4.0 Units (Limit) § C (max) § C (max) § C (max) a 3.0, b 3.5 g 4.0 g 0.8 g 0.8 § C (max) a 9.7 a 10.3 a 9.7 a 10.3 mV/§ C (min) mV/§ C (max) 4000 X (max) 4000 2000 g 0.8 g 0.8 g 1.2 g 1.2 mV/V (max) mV/V (max) a 4.5V s VS s a 10V 130 180 130 180 mA (max) mA (max) a 4.5V s VS s a 10V 2.0 2.0 mA (max) Temperature Coefficient of Quiescent Current Long Term Stability (Note 10) LM50C TJ e 125§ C, for 1000 hours a 1.0 a 2.0 mA/§ C g 0.08 g 0.08 §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 specified without a heat sink, junction to ambient. 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 10mv/§ 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 defined in 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. The majority of the drift will occur in the first 1000 hours at elevated temperatures. The drift after 1000 hours will not continue at the first 1000 hour rate. http://www.national.com 2 Typical Performance Characteristics To generate these curves the LM50 was mounted to a printed circuit board as shown in Figure 2 . Thermal Resistance Junction to Air Thermal Time Constant Thermal Response in Still Air with Heat Sink (Figure 2 ) Thermal Response in Stirred Oil Bath with Heat Sink Start-Up Voltage vs Temperature Thermal Response in Still Air without a Heat Sink Quiescent Current vs Temperature (Figure 1) Accuracy vs Temperature Noise Voltage Supply Voltage vs Supply Current Start-Up Response TL/H/12030 – 19 TL/H/12030 – 18 3 FIGURE 2. Printed Circuit Board Used for Heat Sink to Generate All Curves. (/2× Square Printed Circuit Board with 2 oz. Foil or Similar http://www.national.com 1.0 Mounting 2.0 Capacitive Loads The LM50 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 LM50 die would be at an intermediate temperature between the surface temperature and the air temperature. To ensure good thermal conductivity the backside of the LM50 die is directly attached to the GND pin. The lands and traces to the LM50 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 LM50s temperature to deviate from the desired temperature. Alternatively, the LM50 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 LM50 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 ensure that moisture cannot corrode the LM50 or its connections. TL/H/12030 – 7 FIGURE 3. LM50 No Decoupling Required for Capacitive Load TL/H/12030 – 8 FIGURE 4. LM50C with Filter for Noisy Environment The LM50 handles capacitive loading very well. Without any special precautions, the LM50 can drive any capacitive load. The LM50 has a nominal 2 kX output impedance (as can be seen in the block diagram). The temperature coefficient of the output resistors is around 1300 ppm/§ C. Taking into account this temperature coefficient and the initial tolerance of the resistors the output impedance of the LM50 will not exceed 4 kX. In an extremely noisy environment it may be necessary to add some filtering to minimize noise pickup. It is recommended that 0.1 mF be added from VIN to GND to bypass the power supply voltage, as shown in Figure 4 . In a noisy environment it may be necessary to add a capacitor from the output to ground. A 1 mF output capacitor with the 4 kX output impedance will form a 40 Hz lowpass filter. Since the thermal time constant of the LM50 is much slower than the 25 ms time constant formed by the RC, the overall response time of the LM50 will not be significantly affected. For much larger capacitors this additional time lag will increase the overall response time of the LM50. Temperature Rise of LM50 Due to Self-Heating (Thermal Resistance, iJA) 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 2 . ** Part soldered to 30 gauge wire. TL/H/12030 – 17 *R2 & 2k with a typical 1300 ppm/§ C drift. FIGURE 5. Block Diagram http://www.national.com 4 3.0 Typical Applications TL/H/12030 – 11 FIGURE 6. Centigrade Thermostat/Fan Controller TL/H/12030 – 13 FIGURE 7. Temperature To Digital Converter (Serial Output) ( a 125§ C Full Scale) TL/H/12030 – 14 FIGURE 8. Temperature To Digital Converter (Parallel TRI-STATEÉ Outputs for Standard Data Bus to mP Interface) (125§ C Full Scale) 5 http://www.national.com 3.0 Typical Applications (Continued) TL/H/12030 – 16 FIGURE 9. LM50 With Voltage-To-Frequency Converter And Isolated Output (b40§ C to a 125§ C; 100 Hz to 1750 Hz) 4.0 Recommended Solder Pads for SOT-23 Package SOT-23 TL/H/12030 – 20 http://www.national.com 6 7 http://www.national.com LM50B/LM50C SOT-23 Single-Supply Centigrade Temperature Sensor Physical Dimensions inches (millimeters) unless otherwise noted SOT-23 Molded Small Outline Transistor Package (M3) Order Number LM50BIM3, or LM50CIM3 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 1111 West Bardin Road Arlington, TX 76017 Tel: 1(800) 272-9959 Fax: 1(800) 737-7018 http://www.national.com 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 Europe Fax: a49 (0) 180-530 85 86 Email: europe.support @ nsc.com Deutsch Tel: a49 (0) 180-530 85 85 English Tel: a49 (0) 180-532 78 32 Fran3ais Tel: a49 (0) 180-532 93 58 Italiano Tel: a49 (0) 180-534 16 80 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 Semiconductor Japan Ltd. Tel: 81-043-299-2308 Fax: 81-043-299-2408 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.