LM26 SOT-23, ±3°C Accurate, Factory Preset Thermostat General Description The LM26 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 −55°C to +110°C in 1°C increments. The LM26 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 −10.82mV/°C output slope. Available parts are detailed in the ordering information. For other part options, contact a National Semiconductor Distributor or Sales Representative for information on minimum order qualification. The LM26 is currently available in a 5-lead SOT-23 package. Applications ■ Microprocessor Thermal Management ■ Appliances ■ Portable Battery Powered Systems ■ ■ ■ ■ ■ Fan Control Industrial Process Control HVAC Systems Remote Temperature Sensing Electronic System Protection Features ■ Internal comparator with pin programmable 2°C or 10°C hysteresis ■ No external components required ■ Open Drain or push-pull digital output; supports CMOS ■ ■ ■ ■ ■ ■ logic levels Internal temperature sensor with VTEMP output pin VTEMP output allows after-assembly system testing Internal voltage reference and DAC for trip-point setting Currently available in 5-pin SOT-23 plastic package Excellent power supply noise rejection UL Recognized Component Key Specifications ■ Power Supply Voltage 2.7V to 5.5V ■ Power Supply Current 40µA(max) 20µA(typ) ■ Hysteresis Temperature 2°C or 10°C(typ) Temperature Trip Point Accuracy Temperature Range LM26CIM −55°C to +110°C ±3°C (max) +120°C ±4°C (max) LM26CIM5-TPA Simplified Block Diagram and Connection Diagram 10132301 The LM26CIM5-TPA has a fixed trip point of 85°C. For other trip point and output function availability, please see ordering information or contact National Semiconductor. © 2007 National Semiconductor Corporation 101323 www.national.com LM26 SOT-23, ±3°C Accurate, Factory Preset Thermostat February 2007 LM26 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 3000 Units in Tape & Reel NS Package Number Trip Point Setting Output Function Top Mark LM26CIM5-HHD LM26CIM5X-HHD THHD MA05B 0°C Open Drain US LM26CIM5-NPA LM26CIM5X-NPA TNPA MA05B 45°C Open Drain OS LM26CIM5-PHA LM26CIM5X-PHA TPHA MA05B 50°C Open Drain OS LM26CIM5-RPA LM26CIM5X-RPA TRPA MA05B 65°C Open Drain OS LM26CIM5-SHA LM26CIM5X-SHA TSHA MA05B 70°C Open Drain OS LM26CIM5-SPA LM26CIM5X-SPA TSPA MA05B 75°C Open Drain OS LM26CIM5-TPA LM26CIM5X-TPA TTPA MA05B 85°C Open Drain OS LM26CIM5-VHA LM26CIM5X-VHA TVHA MA05B 90°C Open Drain OS LM26CIM5-VPA LM26CIM5X-VPA TVPA MA05B 95°C Open Drain OS LM26CIM5-XHA LM26CIM5X-XHA TXHA MA05B 100°C Open Drain OS LM26CIM5-XPA LM26CIM5X-XPA TXPA MA05B 105°C Open Drain OS LM26CIM5-YHA LM26CIM5X-YHA TYHA MA05B 110°C Open Drain OS LM26CIM5-YPA LM26CIM5X-YPA TYPA MA05B 115°C Open Drain OS LM26CIM5-ZHA LM26CIM5X-ZHA TZHA MA05B 120°C Open Drain OS Connection Diagram 10132302 Pin Descriptions Pin Number Pin Name Function Connection 1 HYST Hysteresis control, digital input GND for 10°C or V+ for 2°C 2 GND Ground, connected to the back side of the die through lead frame. System GND 3 VTEMP Analog output voltage proportional to temperature Leave floating or connect to a high impedance node. 4 V+ Supply input 2.7V to 5.5V with a 0.1µF bypass capacitor. For PSRR information see Section Titled NOISE CONSIDERATIONS. 5 OS Overtemperature Shutdown open-drain active low thermostat digital output Controller interrupt, system or power supply shutdown; pull-up OS Overtemperature Shutdown push-pull active high thermostat digital output Controller interrupt, system or power supply shutdown US Undertemperature Shutdown open-drain active System or power supply shutdown; pull-up resistor ≥ 10kΩ low thermostat digital output US Undertemperature Shutdown push-pull active high thermostat digital output resistor ≥ 10kΩ System or power supply shutdown Note: pin 5 functionality and trip point setting are programmed during LM26 manufacture. www.national.com 2 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) 6.0V 5mA 20mA Operating Ratings 500mW −65°C to + 150°C 2500V 250V (Note 1) TMIN ≤ TA ≤ TMAX Specified Temperature Range −55°C ≤ TA ≤ +125°C LM26CIM 215°C 220°C Positive Supply Voltage (V+) Maximum VOUT +2.7V to +5.5V +5.5V LM26 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. Symbol Parameter Conditions Typical (Note 6) LM26CIM Limits Units (Limits) (Note 7) Temperature Sensor Trip Point Accuracy (Includes VREF, DAC, -55°C ≤ TA ≤ +110°C Comparator Offset, and Temperature +120°C Sensitivity errors) Trip Point Hysteresis HYST = GND HYST = V+ VTEMP Output Temperature Sensitivity VTEMP Temperature Sensitivity Error to Equation: VO = (−3.479×10−6×(T−30)2) + (−1.082×10−2×(T−30)) + 1.8015V 2.7V ≤ IS °C (max) °C 2 °C mV/°C ±3 °C (max) ±3 °C (max) ±2.5 °C (max) ≤ 5.5V −55°C ≤ TA ≤ 120°C, 4.5V ≤ V+ ≤ 5.5V Source ≤ 1 μA 0.070 Sink ≤ 40 μA VTEMP Line Regulation ±4 −10.82 TA = 30°C VTEMP Load Regulation °C (max) 11 −30°C ≤ TA ≤ 120°C, V+ ±3 +2.7V ≤ ≤ +5.5V, −30°C ≤ TA ≤ +120°C V+ Supply Current mV 0.7 −0.2 mV (max) mV/V 16 20 40 µA (max) µA (max) 0.001 1 µA (max) 0.4 V (max) ISOURCE = 500µA, V+ ≥ 2.7V 0.8 × V+ V (min) ISOURCE = 800µA, V V+ − 1.5 V (min) Digital Output and Input IOUT(“1”) Logical “1” Output Leakage Current (Note 9) V+ = +5.0V VOUT(“0”) Logical “0” Output Voltage IOUT = +1.2mA and ≥2.7V; IOUT = +3.2mA V+ and V+≥4.5V; (Note 8) VOUT(“1”) Logical “1” Push-Pull Output Voltage ≥4.5V + VIH HYST Input Logical ”1“ Threshold Voltage 0.8 × V+ V (min) VIL HYST Input Logical ”0“ Threshold Voltage 0.2 × V+ V (max) 3 www.national.com LM26 Storage Temperature ESD Susceptibility (Note 4) Human Body Model Machine Model Absolute Maximum Ratings (Note 1) LM26 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 θJA SOT23-5, MA05B 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 LM26 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 LM26CIM-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) Temperature (°C) x (10x) A - −5 N y (1x) Temperature (°C) N 4 B - −4 P P 5 C - −3 R R 6 D - −2 S S 7 E - −1 T T 8 F - −0 V V 9 H H 0 X - 10 J J 1 Y - 11 K K 2 Z - 12 L L 3 The value of z describes the assignment/function of the output as shown in the following table: Active-Low/High Open-Drain/ PushPull OS/US Value of z 0 0 0 A Active-Low, Open-Drain, OS output 0 0 1 B Active-Low, Open-Drain, US output 1 1 0 C Active-High, Push-Pull, OS output 1 1 1 D Active-High, Push-Pull, US output Digital Output Function For example: • • the part number LM26CIM5-TPA has TOS = 85°C, and programmed as an active-low open-drain overtemperature shutdown output. the part number LM26CIM5-FPD has TUS = −5°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. www.national.com 4 LM26 Functional Description LM26 OPTIONS 10132312 10132313 LM26-_ _A LM26-_ _B 10132314 10132315 LM26-_ _C LM26-_ _D FIGURE 1. Output Pin Options Block Diagrams The LM26 can be factory programmed to have a trip point anywhere in the range of −55°C to +110°C. 3. Applications Hints AFTER-ASSEMBLY PCB TESTING The LM26's VTEMP output allows after-assembly PCB testing by following a simple test procedure. Simply measuring the VTEMP output voltage will verify that the LM26 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 LM26CIM5-TPA which has an 85°C trip point. 1. Turn on V+ and measure VTEMP. Then calculate the temperature reading of the LM26 using the equation: VO = (−3.479×10−6×(T−30)2) + (−1.082×10−2×(T −30)) + 1.8015V 4. 5. 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 LM26 output, rather than across CLOAD, it should be at least a factor of 10 smaller than CLOAD. (1) or 2. measured using an extremely accurate calibrated temperature sensor. 1. Observe that OS is high. 2. Drive VTEMP to ground. 3. Observe that OS is now low. 4. Release the VTEMP pin. 5. Observe that OS is now high. 1. Observe that OS is high. 2. Drive VTEMP voltage down gradually. 3. When OS goes low, note the VTEMP voltage. 4. VTEMPTrig = VTEMP at OS trigger (HIGH->LOW) 5. Calculate Ttrig using Equation 2. 1. Gradually raise VTEMP until OS goes HIGH. Note VTEMP. 2. Calculate THYST using Equation 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 5 www.national.com LM26 mented to a surface. The temperature that the LM26 is sensing will be within about +0.06°C of the surface temperature to which the LM26'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 LM26 die is directly attached to the GND pin (pin 2). The temperatures of the lands and traces to the other leads of the LM26 will also affect the temperature that is being sensed. Alternatively, the LM26 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 LM26 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 LM26 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 LM26 the equation used to calculate the rise in the die junction temperature is as follows: TABLE 1. Resistive compensation for capacitive loading of VTEMP CLOAD R (Ω) ≤100pF 0 1nF 8200 10nF 3000 100nF 1000 ≥1µF 430 10132317 a) R in series with capacitor (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 LM26's junction temperature is the actual temperature being measured, care should be taken to minimize the load current that the LM26 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 LM26 without any loading on VTEMP and a 10k pull-up resistor on an open-drain digital output with a 5.5V power supply. 10132318 b) R in series with signal path FIGURE 2. Resistor placement for capacitive loading compensation of VTEMP NOISE CONSIDERATIONS The LM26 has excellent power supply noise rejection. Listed below is a variety of signals used to test the LM26 power supply rejection. False triggering of the output was not observed when these signals where coupled into the V+ pin of the LM26. • 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 LM26 one degree centigrade way from the trip point with the output not activated. SOT23-5 no heat sink θJA θJA (°C/W) TJ−TA (°C) (°C/W) TJ−TA (°C) Still Air 250 0.11 TBD TBD Moving Air TBD TBD TBD TBD FIGURE 3. Thermal resistance (θJA) and temperature rise due to self heating (TJ−TA) MOUNTING CONSIDERATIONS The LM26 can be applied easily in the same way as other integrated-circuit temperature sensors. It can be glued or ce- www.national.com SOT23-5 small heat sink 6 LM26 Typical Applications 10132303 Note: The fan's control pin has internal pull-up. The 10k pull-down sets a slow fan speed. When the output of the LM26 goes low, the fan will speed up. FIGURE 4. Two Speed Fan Speed Control 10132320 FIGURE 5. Fan High Side Drive 10132321 FIGURE 6. Fan Low Side Drive 7 www.national.com LM26 10132322 FIGURE 7. Audio Power Amplifier Thermal Protection 10132323 FIGURE 8. Simple Thermostat www.national.com 8 LM26 Physical Dimensions inches (millimeters) unless otherwise noted 5-Lead Molded SOT-23 Plastic Package, JEDEC Order Number LM26CIM5 or LM26CIM5X NS Package Number MA05B 9 www.national.com LM26 SOT-23, ±3°C Accurate, Factory Preset Thermostat Notes THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS, IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT NATIONAL’S PRODUCT WARRANTY. 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