LM62_05

LM62 2.7V, 15.6 mV/˚C, SOT-23 Temperature Sensor August 2005 LM62 2.7V, 15.6 mV/˚C SOT-23 Temperature Sensor General Description The LM62 is a precision integrated-circuit temperature sensor that can sense a 0˚C to +90˚C temperature range while operating from a single +3.0V supply. The LM62’s output voltage is linearly proportional to Celsius (Centigrade) temperature (+15.6 mV/˚C) and has a DC offset of +480 mV. The offset allows reading temperatures down to 0˚C without the need for a negative supply. The nominal output voltage of the LM62 ranges from +480 mV to +1884 mV for a 0˚C to +90˚C temperature range. The LM62 is calibrated to provide accuracies of ± 2.0˚C at room temperature and +2.5˚C/ −2.0˚C over the full 0˚C to +90˚C temperature range. The LM62’s linear output, +480 mV offset, and factory calibration simplify external circuitry required in a single supply environment where reading temperatures down to 0˚C is required. Because the LM62’s quiescent current is less than 130 µA, self-heating is limited to a very low 0.2˚C in still air. Shutdown capability for the LM62 is intrinsic because its inherent low power consumption allows it to be powered directly from the output of many logic gates. Features n Calibrated linear scale factor of +15.6 mV/˚C n Rated for full 0˚C to +90˚C range with 3.0V supply n Suitable for remote applications Applications n n n n n n n n n Cellular Phones Computers Power Supply Modules Battery Management FAX Machines Printers HVAC Disk Drives Appliances Key Specifications n n n n n n Accuracy at 25˚C Temperature Slope Power Supply Voltage Range Current Drain @ 25˚C Nonlinearity Output Impedance ± 2.0 or ± 3.0˚C (max) +15.6 mV/˚C +2.7V to +10V 130 µA (max) ± 0.8˚C (max) 4.7 kΩ (max) Connection Diagram SOT-23 Typical Application 10089301 Top View See NS Package Number mf03a VO = (+15.6 mV/˚C x T˚C) + 480 mV 10089302 Ordering Information Order Number LM62BIM3 LM62BIM3X LM62CIM3 LM62CIM3X Device Top Mark T7B T7B T7C T7C Supplied As 1000 Units, Tape and Reel 3000 Units, Tape and Reel 1000 Units, Tape and Reel 3000 Units, Tape and Reel Temperature (T) +90˚C +70˚C +25˚C 0˚C Typical VO +1884 mV +1572 mV 870 mV +480 mV FIGURE 1. Full-Range Centigrade Temperature Sensor (0˚C to +90˚C) Stabilizing a Crystal Oscillator © 2005 National Semiconductor Corporation DS100893 www.national.com LM62 Absolute Maximum Ratings (Note 1) Supply Voltage Output Voltage Output Current Input Current at any pin (Note 2) Storage Temperature Junction Temperature, max (TJMAX) ESD Susceptibility (Note 3) : Human Body Model 2500V +12V to −0.2V (+VS + 0.6V) to −0.6V 10 mA 5 mA −65˚C to +150˚C +125˚C Machine Model 250V Operating Ratings(Note 1) Specified Temperature Range: LM62B, LM62C Supply Voltage Range (+VS) Thermal Resistance, θJA(Note 5) TMIN ≤ TA ≤ TMAX 0˚C ≤ TA ≤ +90˚C +2.7V to +10V 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. Boldface limits apply for TA = TJ = TMIN to TMAX ; all other limits TA = TJ = 25˚C. Parameter Conditions Typical (Note 6) LM62B Limits (Note 7) Accuracy (Note 8) Output Voltage at 0˚C Nonlinearity (Note 9) Sensor Gain (Average Slope) Output Impedance Line Regulation (Note 10) Quiescent Current Change of Quiescent Current Temperature Coefficient of Quiescent Current Long Term Stability (Note 11) TJ=TMAX=+100˚C, for 1000 hours +3.0V ≤ +VS ≤ +10V 0˚C ≤ TA ≤ +75˚C, +VS= +2.7V +3.0V ≤ +VS ≤ +10V +2.7V ≤ +VS ≤ +3.3V, 0˚C ≤ TA ≤ +75˚C +2.7V ≤ +VS ≤ +10V +2.7V ≤ +VS ≤ +10V 82 +16 +480 LM62C Limits (Note 7) Units (Limit) ˚C (max) ˚C (max) mV ˚C (max) mV/˚C (max) mV/˚C (min) kΩ (max) kΩ (max) mV/V (max) mV (max) µA (max) µA (max) µA µA/˚C ± 2.0 +2.5/−2.0 ± 3.0 +4.0/−3.0 ± 0.8 +16.1 +15.1 4.7 4.4 ± 1.0 +16.3 +14.9 4.7 4.4 ± 1.13 ± 9.7 130 165 ± 1.13 ± 9.7 130 165 ±5 0.2 ± 0.2 ˚C 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 +15.6 mV/˚C times the device’s case temperature plus 480 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. www.national.com 2 LM62 Typical Performance Characteristics printed circuit board as shown in Figure 2. Thermal Resistance Junction to Air To generate these curves the LM62 was mounted to a Thermal Time Constant 10089303 10089304 Thermal Response in Still Air with Heat Sink Thermal Response in Stirred Oil Bath with Heat Sink 10089305 10089306 Thermal Response in Still Air without a Heat Sink Quiescent Current vs. Temperature 10089308 10089309 3 www.national.com LM62 Typical Performance Characteristics To generate these curves the LM62 was mounted to a printed circuit board as shown in Figure 2. (Continued) Accuracy vs Temperature Noise Voltage 10089310 10089311 Supply Voltage vs Supply Current Start-Up Response 10089322 10089312 Circuit Board 10089314 Printed Circuit Board Used for Heat Sink to Generate All Curves. 1⁄2" Square Printed Circuit Board with 2 oz. Copper Foil or Similar. FIGURE 2. www.national.com 4 LM62 1.0 Mounting The LM62 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 LM62 is sensing will be within about +0.2˚C of the surface temperature that LM62’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 measured would be at an intermediate temperature between the surface temperature and the air temperature. To ensure good thermal conductivity the backside of the LM62 die is directly attached to the GND pin. The lands and traces to the LM62 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 LM62’s temperature to deviate from the desired temperature. Alternatively, the LM62 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 LM62 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 LM62 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 its power dissipation. For the LM62 the equation used to calculate the rise in the die temperature is as follows: TJ = TA + θJA [(+VS IQ) + (+VS − VO) IL] where IQ is the quiescent current and ILis the load current on the output. Since the LM62’s junction temperature is the actual temperature being measured care should be taken to minimize the load current that the LM62 is required to drive. The table shown in Figure 3 summarizes the rise in die temperature of the LM62 without any loading, and the thermal resistance for different conditions. SOT-23 no heat sink (Note 13) θJA (˚C/W) Still air Moving air 450 TJ − T A (˚C) 0.17 SOT-23 small heat fin (Note 12) θJA (˚C/W) 260 180 TJ − T A (˚C) 0.1 0.07 2.0 Capacitive Loads The LM62 handles capacitive loading well. Without any special precautions, the LM62 can drive any capacitive load as shown in Figure 4. Over the specified temperature range the LM62 has a maximum output impedance of 4.7 kΩ. 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 +VS 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 4.7 kΩ maximum output impedance will form a 34 Hz lowpass filter. Since the thermal time constant of the LM62 is much slower than the 30 ms time constant formed by the RC, the overall response time of the LM62 will not be significantly affected. For much larger capacitors this additional time lag will increase the overall response time of the LM62. 10089315 FIGURE 4. LM62 No Decoupling Required for Capacitive Load 10089316 FIGURE 5. LM62 with Filter for Noisy Environment Note 12: Heat sink used is 1⁄2" square printed circuit board with 2 oz. foil with part attached as shown in Figure 2 . Note 13: Part soldered to 30 gauge wire. FIGURE 3. Temperature Rise of LM62 Due to Self-Heating and Thermal Resistance (θJA) 5 www.national.com LM62 2.0 Capacitive Loads (Continued) 10089317 FIGURE 6. Simplified Schematic 3.0 Applications Circuits 10089318 FIGURE 7. Centigrade Thermostat 10089319 FIGURE 8. Conserving Power Dissipation with Shutdown www.national.com 6 LM62 2.7V, 15.6 mV/˚C, SOT-23 Temperature Sensor Physical Dimensions inches (millimeters) unless otherwise noted SOT-23 Molded Small Outline Transistor Package (M3) Order Number LM62BIM3 or LM62CIM3 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. 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