LM27_06

LM27 SOT-23, ± 3˚C Accurate, 120˚C-150˚C Factory Preset Thermostat September 2006 LM27 SOT-23, ± 3˚C Accurate, 120˚C-150˚C Factory Preset Thermostat General Description The LM27 is a precision, single digital-output, low-power thermostat comprised of an internal reference, DAC, temperature sensor and comparator. Utilizing factory programming, it can be manufactured with different trip points as well as different digital output functionality. The trip point (TOS) can be preset at the factory to any temperature in the range of +120˚C to +150˚C in 1˚C increments. The LM27 has one digital output (OS/OS/US/US), one digital input (HYST) and one analog output (VTEMP). The digital output stage can be preset as either open-drain or push-pull. In addition, it can be factory programmed to be active HIGH or LOW. The digital output can be factory programmed to indicate an over temperature shutdown event (OS or OS) or an under temperature shutdown event (US or US). When preset as an overtemperature shutdown (OS) it will go LOW to indicate that the die temperature is over the internally preset TOS and go HIGH when the temperature goes below (TOS–THYST). Similarly, when preprogrammed as an undertemperature shutdown (US) it will go HIGH to indicate that the temperature is below TUS and go LOW when the temperature is above (TUS+THYST). The typical hysteresis, THYST, can be set to 2˚C or 10˚C and is controlled by the state of the HYST pin. A VTEMP analog output provides a voltage that is proportional to temperature and has a −10.7mV/˚C output slope. Currently, there are several standard parts available, see ordering information for details. For other part options, contact a National Semiconductor Distributor or Sales Representative for information on minimum order qualification. The LM27 is currently available in a 5-lead SOT-23 package. Applications n n n n n n n Microprocessor Thermal Management Appliances Portable Battery Powered Systems Fan Control Industrial Process Control HVAC Systems Electronic System Protection Features n Internal comparator with pin selectable 2˚C or 10˚C hysteresis n No external components required n Open-drain or push-pull digital output; supports CMOS logic levels n Internal temperature sensor with VTEMP output pin n VTEMP output allows after-assembly system testing n Internal voltage reference and DAC for trip-point setting n Currently available in 5-pin SOT-23 plastic package n Excellent power supply noise rejection Key Specifications j Power Supply Voltage j Power Supply Current j Hysteresis Temperature j Temperature Trip Point Accuracy 2.7V to 5.5V 40µA(max) 15µA(typ) 2˚C or 10˚C(typ) ± 3˚C (max) LM27CIM5-2HJ Simplified Block Diagram and Connection Diagram 20030701 The LM27CIM5-2HJ has a fixed trip point of 140˚C. For other trip point and output function availability, please see ordering information or contact National Semiconductor. © 2006 National Semiconductor Corporation DS200307 www.national.com LM27 Ordering Information For more detailed information on the suffix meaning see the part number template at the end of the Electrical Characteristics Section. Contact National Semiconductor for other set points and output options. Order Number Bulk Rail LM27CIM5-ZHJ LM27CIM5-1HJ LM27CIM5-2HJ 3000 Units in Tape & Reel LM27CIM5X-ZHJ LM27CIM5X-1HJ LM27CIM5X-2HJ Top Mark TZHJ T1HJ T2HJ NS Package Number MA05B MA05B MA05B Trip Point Setting 120˚C 130˚C 140˚C Output Function Open Drain OS Open Drain OS Open Drain OS Connection Diagram 20030702 Pin Descriptions Pin Number 1 2 Pin Name HYST GND Function Hysteresis control, digital input Ground, connected to the back side of the die through lead frame. Analog output voltage proportional to temperature Supply input Connection GND for 10˚C or V+ for 2˚C System GND 3 4 VTEMP V+ Leave floating or connect to a high impedance node. 2.7V to 5.5V with a 0.1µF bypass capacitor. For PSRR information see Section Titled NOISE CONSIDERATIONS. Controller interrupt, system or power supply shutdown; pull-up resistor ≥ 10kΩ Controller interrupt, system or power supply shutdown System or power supply shutdown; pull-up resistor ≥ 10kΩ System or power supply shutdown 5 OS Overtemperature Shutdown open-drain active low thermostat digital output Overtemperature Shutdown totem-pull active high thermostat digital output Undertemperature Shutdown open-drain active low thermostat digital output Undertemperature Shutdown totem-pull active high thermostat digital output OS US US Note: pin 5 functionality and trip point setting are programmed during LM27 manufacture. www.national.com 2 LM27 Absolute Maximum Ratings (Note 1) Input Voltage Input Current at any pin (Note 2) Package Input Current(Note 2) Package Dissipation at TA = 25˚C (Note 3) Soldering Information SOT23 Package Vapor Phase (60 seconds) Infrared (15 seconds) Storage Temperature 6.0V 5mA 20mA 500mW ESD Susceptibility (Note 4) Human Body Model Machine Model 2500V 250V Operating Ratings(Note 1) Specified Temperature Range LM27CIM Positive Supply Voltage (V+) TMIN ≤ TA ≤ TMAX −40˚C ≤ TA ≤ +150˚C +2.7V to +5.5V +5.5V 215˚C 220˚C −65˚C to + 150˚C Maximum VOUT LM27 Electrical Characteristics The following specifications apply for V+ = 2.7VDC to 5.5VDC, and VTEMP load current = 0µA unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C unless otherwise specified. Typical Symbol Temperature Sensor Trip Point Accuracy (Includes VREF, DAC, Comparator Offset, and Temperature Sensitivity errors) Trip Point Hysteresis VTEMP Output Temperature Sensitivity VTEMP Temperature Sensitivity Error to Equation: VO = (−3.552x10−6x(T−30)2+ (−10.695x10−3x(T−30))+ 1.8386V VTEMP Load Regulation VTEMP Line Regulation IS Supply Current −30˚C ≤ TA ≤ 150˚C, 2.7V ≤ V+ ≤ 5.5V −55˚C ≤ TA ≤ 150˚C, 4.5V ≤ V+ ≤ 5.5V TA = 25˚C Source ≤ 1 µA Sink ≤ 40 µA +2.7V ≤ V+ ≤ +5.5V, −30˚C ≤ TA ≤ +120˚C −0.2 15 22 40 1 0.4 0.070 0.7 +120˚C < TA < +150˚C Parameter Conditions (Note 6) LM27CIM Limits (Note 7) Units (Limits) ±3 ˚C (max) HYST = GND HYST = V + 10 2 −10.82 ˚C ˚C mV/˚C ±3 ±3 ± 2.5 ˚C (max) ˚C (max) ˚C (max) mV mV (max) mV/V µA (max) µA (max) µA (max) V (max) Digital Output and Input IOUT(“1”) VOUT(“0”) Logical “1” Output Leakage Current (Note 9) Logical “0” Output Voltage V+ = +5.0V IOUT = +1.2mA and V+≥2.7V; IOUT = +3.2mA and V+≥4.5V; (Note 8) ISOURCE = 500µA, V+ ≥ 2.7V ISOURCE = 800µA, V+≥4.5V VIH VIL HYST Input Logical ”1“ Threshold Voltage HYST Input Logical ”0“ Threshold Voltage 0.001 VOUT(“1”) Logical “1” Push-Pull Output Voltage 0.8 x V+ V+ − 1.5 0.8 x V+ 0.2 x V+ V (min) V (min) V (min) V (max) 3 www.national.com LM27 LM27 Electrical Characteristics (Continued) 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 the power supply (VI < GND or VI > V+), the current at that pin should be limited to 5mA. The 20mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5mA to four. Under normal operating conditions the maximum current that pins 2, 4 or 5 can handle is limited to 5mA each. Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature), θJA (junction to ambient thermal resistance) and TA (ambient temperature). The maximum allowable power dissipation at any temperature is PD = (TJmax–TA)/θJA or the number given in the Absolute Maximum Ratings, whichever is lower. For this device, TJmax = 150˚C. For this device the typical thermal resistance (θJA) of the different package types when board mounted follow: Package Type SOT23-5, MA05B θJA 250˚C/W Note 4: The human body model is a 100pF capacitor discharge through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor discharged directly into each pin. Note 5: See the URL ”http://www.national.com/packaging/“ for other recommendations and methods of soldering surface mount devices. 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: Care should be taken to include the effects of self heating when setting the maximum output load current. The power dissipation of the LM27 would increase by 1.28mW when IOUT=3.2mA and VOUT=0.4V. With a thermal resistance of 250˚C/W, this power dissipation would cause an increase in the die temperature of about 0.32˚C due to self heating. Self heating is not included in the trip point accuracy specification. Note 9: The 1µA limit is based on a testing limitation and does not reflect the actual performance of the part. Expect to see a doubling of the current for every 15˚C increase in temperature. For example, the 1nA typical current at 25˚C would increase to 16nA at 85˚C. Part Number Template The series of digits labeled xyz in the part number LM27CIM-xyz, describe the set point value and the function of the output as follows: The place holders xy describe the set point temperature as shown in the following table. x (10x) y (1x) H J K L N P R Temperature (˚C) 0 1 2 3 4 5 6 x (10x) Z 1 2 3 y (1x) S T V Temperature (˚C) 7 8 9 12 13 14 15 The value of z describes the assignment/function of the output as shown in the following table: Active-Low/High 0 0 1 1 For example: the part number LM27CIM5-2SJ has TOS = 147˚C, and programmed as an active-low open-drain overtemperature shutdown output. • the part number LM27CIM5-ZLN has TUS = 123˚C, and programmed as an active-high, push-pull undertemperature shutdown output. Active-high open-drain and active-low push-pull options are available, please contact National Semiconductor for more information. Open-Drain/ Push-Pull 0 0 1 1 OS/US 0 1 0 1 Value of z J K L N Digital Output Function Active-Low, Open-Drain, OS output Active-Low, Open-Drain, US output Active-High, Push-Pull, OS output Active-High, Push-Pull, US output • www.national.com 4 LM27 Functional Description LM27 OPTIONS 20030712 20030713 LM27-_ _J LM27-_ _K 20030714 20030715 LM27-_ _L FIGURE 1. Output Pin Options Block Diagrams The LM27 can be factory programmed to have a trip point anywhere in-between 120˚C to 150˚C. LM27-_ _N board temperature not the ambient temperature (see Section Titled Mounting Considerations) 3. A. B. C. D. E. 4. A. B. C. D. 5. A. Gradually raise VTEMP until OS goes HIGH. Note VTEMP. B. Calculate THYST using Equation (2). VTEMP LOADING The VTEMP output has very weak drive capability (1 µA source, 40 µA sink). So care should be taken when attaching circuitry to this pin. Capacitive loading may cause the VTEMP output to oscillate. Simply adding a resistor in series as shown in Figure 2 will prevent oscillations from occurring. To determine the value of the resistor follow the guidelines given in Table 1. The same value resistor will work for either placement of the resistor. If an additional capacitive load is placed directly on the LM27 output, rather than across CLOAD, it should be at least a factor of 10 smaller than CLOAD. Observe that OS is high. Drive VTEMP voltage down gradually. When OS goes low, note the VTEMP voltage. VTEMPTrig = VTEMP at OS trigger (HIGH- > LOW) Observe that OS is high. Drive VTEMP to ground. Observe that OS is now low. Release the VTEMP pin. Observe that OS is now high. Applications Hints AFTER-ASSEMBLY PCB TESTING The LM27’s VTEMP output allows after-assembly PCB testing by following a simple test procedure. Simply measuring the VTEMP output voltage will verify that the LM27 has been assembled properly and that its temperature sensing circuitry is functional. The VTEMP output has very weak drive capability that can be overdriven by 1.5mA. Therefore, one can simply force the VTEMP voltage to cause the digital output to change state, thereby verifying that the comparator and output circuitry function after assembly. Here is a sample test procedure that can be used to test the LM27CIM5X-2HJ which has a 140˚C trip point. 1. Turn on V+ and measure VTEMP. Then calculate the temperature reading of the LM27 using the equation: VO = (−3.552x10−6x(T−30)2) + (1) (−10.69576x10−3x(T−30)) + 1.8386V or E. Calculate Ttrig using Equation (2). 2. (2) Verify that the temperature measured in step one is within ( ± 3˚C + error of reference temperature sensor) of the ambient/board temperature. The ambient/board temperature (reference temperature) should be measured using an extremely accurate calibrated temperature sensor, which is in close proximity to and mounted on the same PCB as the LM27 perhaps even touching the GND lead of the LM27 if possible. The LM27 will sence the 5 www.national.com LM27 Applications Hints (Continued) TABLE 1. Resistive compensation for capacitive loading of VTEMP CLOAD ≤100pF 1nF 10nF 100nF ≥1µF R (Ω) 0 8200 3000 1000 430 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 LM27 die is directly attached to the GND pin (pin 2). The temperatures of the lands and traces to the other leads of the LM27 will also affect the temperature that is being sensed. Alternatively, the LM27 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 LM27 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 LM27 or its connections. The junction to ambient thermal resistance (θJA) is the parameter used to calculate the rise of a part’s junction temperature due to its power dissipation. For the LM27 the equation used to calculate the rise in the die junction temperature is as follows: 20030717 a) R in series with capacitor 20030718 b) R in series with signal path FIGURE 2. Resistor placement for capacitive loading compensation of VTEMP (3) where TA is the ambient temperature, V+ is the power supply voltage, IQ is the quiescent current, IL_TEMP is the load current on the VTEMP output, VDO is the voltage on the digital output, and IDO is the load current on the digital output. Since the LM27’s junction temperature is the actual temperature being measured, care should be taken to minimize the load current that the LM27 is required to drive. The tables shown in Figure 3 summarize the thermal resistance for different conditions and the rise in die temperature of the LM27 without any loading on VTEMP and a 10k pull-up resistor on an open-drain digital output with a 5.5V power supply. SOT23-5 no heat sink θJA (˚C/W) Still Air Moving Air 250 TBD TJ−TA (˚C) 0.11 TBD SOT23-5 small heat sink θJA (˚C/W) TBD TBD TJ−TA (˚C) TBD TBD NOISE CONSIDERATIONS The LM27 has excellent power supply noise rejection. Listed below is a variety of signals used to test the LM27 power supply rejection. False triggering of the output was not observed when these signals where coupled into the V+ pin of the LM27. • square wave 400kHz, 1Vp-p • square wave 2kHz, 200mVp-p • sine wave 100Hz to 1MHz, 200mVp-p Testing was done while maintaining the temperature of the LM27 one degree centigrade way from the trip point with the output not activated. MOUNTING CONSIDERATIONS The LM27 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 LM27 is sensing will be within about +0.06˚C of the surface temperature to which the LM27’s leads are attached to. FIGURE 3. Thermal resistance (θJA) and temperature rise due to self heating (TJ−TA) www.national.com 6 LM27 Typical Applications 20030703 Note: The fan’s control pin has internal pull-up. The 10k pull-down sets a slow fan speed. When the output of the LM27 goes low, the fan will speed up. FIGURE 4. Two Speed Fan Speed Control 20030720 FIGURE 5. Fan High Side Drive 20030721 FIGURE 6. Fan Low Side Drive 7 www.national.com LM27 Typical Applications (Continued) 20030722 FIGURE 7. Audio Power Amplifier Thermal Protection 20030723 FIGURE 8. Simple Thermostat www.national.com 8 LM27 SOT-23, ± 3˚C Accurate, 120˚C-150˚C Factory Preset Thermostat Physical Dimensions inches (millimeters) unless otherwise noted 5-Lead Molded SOT-23 Plastic Package, JEDEC Order Number LM27CIM5 or LM27CIM5X NS Package Number MA05B 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. 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National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.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. LM27 SOT-23, ± 3˚C Accurate, 120˚C-150˚C Factory Preset Thermostat www.national.com Tel: 81-3-5639-7560