SM73710 SM73710 2.7V, SOT-23 Temperature Sensor Literature Number: SNOSBA1 SM73710 2.7V, SOT-23 Temperature Sensor General Description Applications The SM73710 is a precision integrated-circuit temperature sensor that can sense a −40°C to +125°C temperature range while operating from a single +2.7V supply. The SM73710's output voltage is linearly proportional to Celsius (Centigrade) temperature (+6.25 mV/°C) and has a DC offset of +424 mV. The offset allows reading negative temperatures without the need for a negative supply. The nominal output voltage of the SM73710 ranges from +174 mV to +1205 mV for a −40°C to +125°C temperature range. The SM73710 is calibrated to provide accuracies of ±2.0°C at room temperature and ±4°C over the full −40°C to +125°C temperature range. The SM73710's linear output, +424 mV offset, and factory calibration simplify external circuitry required in a single supply environment where reading negative temperatures is required. Because the SM73710's quiescent current is less than 110 μA, self-heating is limited to a very low 0.1°C in still air in the SOT-23 package. Shutdown capability for the SM73710 is intrinsic because its inherent low power consumption allows it to be powered directly from the output of many logic gates. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Features ■ ■ ■ ■ ■ Renewable Energy Grade Calibrated linear scale factor of +6.25 mV/°C Rated for full −40°C to +125°C range Suitable for remote applications Available in SOT-23 package Photovoltaic Electronics Cellular Phones Computers Power Supply Modules Battery Management FAX Machines Printers HVAC Disk Drives Appliances Key Specifications ■ ■ ■ ■ ■ ■ ■ Accuracy at 25°C: ±3.0°C (max) Accuracy for −40°C to +125°C: ±4.0°C (max) Temperature Slope: +6.25mV/°C Power Supply Voltage Range: +2.7V to +10V Current Drain @ 25°C: 110μA (max) Nonlinearity: ±0.8°C (max) Output Impedance: 800Ω (max) Connection Diagram Typical Application SOT-23 30159801 30159802 VO = (+6.25 mV/°C × T °C) + 424 mV Temperature (T) Typical VO +125°C +1205 mV +100°C +1049 mV +25°C +580 mV 0°C +424 mV −25°C +268 mV −40°C +174 mV Top View See NS Package Number MF03A FIGURE 1. Full-Range Centigrade Temperature Sensor (−40°C to +125°C) Operating from a Single Li-Ion Battery Cell © 2011 National Semiconductor Corporation 301598 www.national.com SM73710 2.7V, SOT-23 Temperature Sensor October 5, 2011 SM73710 Ordering Information Order Number Device Top Mark Supplied In SM73710MF S737 1000 Units, Tape and Reel SM73710MFE S737 250 Units, Tape and Reel SM73710MFX S737 3000 Units, Tape and Reel www.national.com 2 NSC Package Drawing Package Type MF03A SOT-23 Supply Voltage Output Voltage Output Current Input Current at any pin (Note 2) ESD Susceptibility (Note 3) : Human Body Model Machine Model +12V to −0.2V (+VS + 0.6V) to −0.6V 10 mA 5 mA Operating Ratings +125°C (Note 1) Specified Temperature Range: TMIN ≤ TA ≤ TMAX −40°C ≤ TA ≤ +125°C SM73710 Supply Voltage Range (+VS) 2500V 250V −65°C to +150°C +2.7V to +10V Thermal Resistance, θJA (Note 5) 450°C/W Soldering process must comply with National Semiconductor's Reflow Temperature Profile specifications. Refer to www.national.com/packaging. (Note 4) Electrical Characteristics Unless otherwise noted, these specifications apply for +VS = +3.0 VDC and I LOAD = 1 μA. Boldface limits apply for TA = TJ = TMIN to TMAX ; all other limits TA = TJ = 25°C. Parameter Limits (Note 7) Units (Limit) ±3.0 ±4.0 °C (max) °C (max) ±0.8 °C (max) +6.00 +6.50 mV/°C (min) mV/°C (max) 800 Ω (max) +3.0V ≤ +V S ≤ +10V ±0.3 mV/V (max) +2.7V ≤ +V S ≤ +3.3V ±2.3 mV (max) 110 μA (max) 125 μA (max) Conditions Typical (Note 6) Accuracy (Note 8) Output Voltage at 0°C +424 Nonlinearity (Note 9) Sensor Gain (Average Slope) +6.25 Output Impedance Line Regulation (Note 10) Quiescent Current Change of Quiescent Current +2.7V ≤ +V S ≤ +10V +2.7V ≤ +V S ≤ +10V Temperature Coefficient of 82 mV ±5.0 μA (max) 0.2 μA/°C ±0.2 °C Quiescent Current Long Term Stability (Note 11) T J=TMAX=+125°C, for 1000 hours Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test conditions. Note 2: When the input voltage (VI) at any pin exceeds power supplies (VI < GND or VI > +VS), the current at that pin should be limited to 5 mA. Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin. Note 4: Reflow temperature profiles are different for lead-free and non-lead-free packages. Note 5: The junction to ambient thermal resistance (θJA) is specified without a heat sink in still air. Note 6: Typicals are at TJ = TA = 25°C and represent most likely parametric norm. Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level). Note 8: Accuracy is defined as the error between the output voltage and +6.25 mV/°C times the device's case temperature plus 424 mV, at specified conditions of voltage, current, and temperature (expressed in °C). 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: 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 11: 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. 3 www.national.com SM73710 Storage Temperature Maximum Junction Temperature (TJMAX) Absolute Maximum Ratings (Note 1) SM73710 Typical Performance Characteristics To generate these curves the SM73710 was mounted to a printed circuit board as shown in Figure 2. Thermal Resistance Junction to Air Thermal Time Constant 30159804 30159803 Thermal Response in Still Air with Heat Sink Thermal Response in Stirred Oil Bath with Heat Sink 30159805 30159806 Start-Up Voltage vs. Temperature Thermal Response in Still Air without a Heat Sink 30159807 www.national.com 30159808 4 SM73710 Quiescent Current vs. Temperature Accuracy vs Temperature 30159810 30159809 Noise Voltage Supply Voltage vs Supply Current 30159811 30159812 Start-Up Response 30159822 5 www.national.com SM73710 30159814 FIGURE 2. Printed Circuit Board Used for Heat Sink to Generate All Curves. ½″ Square Printed Circuit Board with 2 oz. Copper Foil or Similar. into a threaded hole in a tank. As with any IC, the SM73710 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 SM73710 or its connections. The thermal resistance junction to ambient (θJA ) is the parameter used to calculate the rise of a device junction temperature due to the device power dissipation. For the SM73710 the equation used to calculate the rise in the die temperature is as follows: TJ = TA + θ JA [(+VS IQ) + (+VS − VO) IL] where IQ is the quiescent current and ILis the load current on the output. The table shown in Figure 3 summarizes the rise in die temperature of the SM73710 without any loading, and the thermal resistance for different conditions. 1.0 Mounting The SM73710 can be applied easily in the same way as other integrated-circuit temperature sensors. It can be glued or cemented to a surface. The temperature that the SM73710 is sensing will be within about +0.1°C of the surface temperature that SM73710's leads are attached to. 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 SM73710 die would be at an intermediate temperature between the surface temperature and the air temperature. To ensure good thermal conductivity the backside of the SM73710 die is directly attached to the GND pin. The lands and traces to the SM73710 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 SM73710's temperature to deviate from the desired temperature. Alternatively, the SM73710 can be mounted inside a sealedend metal tube, and can then be dipped into a bath or screwed SOT-23* no heat sink Still air SOT-23** small heat fin θ JA T J − TA θ JA T J − TA (°C/W) (°C) (°C/W) (°C) 450 0.17 260 0.1 180 0.07 Moving air *-Part soldered to 30 gauge wire. **-Heat sink used is ½″ square printed circuit board with 2 oz. foil with part attached as shown in Figure 2 . FIGURE 3. Temperature Rise of SM73710 Due to Self-Heating and Thermal Resistance (θJA) www.national.com 6 SM73710 2.0 Capacitive Loads The SM73710 handles capacitive loading well. Without any special precautions, the SM73710 can drive any capacitive load as shown in Figure 4. Over the specified temperature range the SM73710 has a maximum output impedance of 800Ω. In an extremely noisy environment it may be necessary to add some filtering to minimize noise pickup. It is recommended that 0.1 μF be added from +V S to GND to bypass the power supply voltage, as shown in Figure 5. In a noisy environment it may be necessary to add a capacitor from the output to ground. A 1 μF output capacitor with the 800Ω output impedance will form a 199 Hz lowpass filter. Since the thermal time constant of the SM73710 is much slower than the 6.3 ms time constant formed by the RC, the overall response time of the SM73710 will not be significantly affected. For much larger capacitors this additional time lag will increase the overall response time of the SM73710. 30159816 FIGURE 5. SM73710 with Filter for Noisy Environment 30159815 FIGURE 4. SM73710 No Decoupling Required for Capacitive Load 30159817 FIGURE 6. Simplified Schematic 7 www.national.com SM73710 3.0 Applications Circuits 30159818 FIGURE 7. Centigrade Thermostat 30159819 FIGURE 8. Conserving Power Dissipation with Shutdown www.national.com 8 SM73710 Physical Dimensions inches (millimeters) unless otherwise noted SOT-23 Molded Small Outline Transistor Package (MF) NS Package Number MF03A 9 www.national.com SM73710 2.7V, SOT-23 Temperature Sensor Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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