Low Voltage Temperature Sensors TMP35/TMP36/TMP37 Environmental control systems Thermal protection Industrial process control Fire alarms Power system monitors CPU thermal management GENERAL DESCRIPTION The TMP35/TMP36/TMP37 are low voltage, precision centigrade temperature sensors. They provide a voltage output that is linearly proportional to the Celsius (centigrade) temperature. The TMP35/ TMP36/TMP37 do not require any external calibration to provide typical accuracies of 1C at +25C and 2C over the -40C to +125C temperature range. The low output impedance of the TMP35/TMP36/TMP37 and its linear output and precise calibration simplify interfacing to temperature control circuitry and ADCs. All three devices are intended for single-supply operation from 2.7 V to 5.5 V maximum. The supply current runs well below 50 A, providing very low self-heating--less than 0.1C in still air. In addition, a shutdown function is provided to cut the supply current to less than 0.5 A. The TMP35 is functionally compatible with the LM35/LM45 and provides a 250 mV output at 25C. The TMP35 reads temperatures from 10C to 125C. The TMP36 is specified from -40C to +125C, provides a 750 mV output at 25C, and operates to 125C from a single 2.7 V supply. The TMP36 is functionally compatible with the LM50. Both the TMP35 and TMP36 have an output scale factor of 10 mV/C. +VS (2.7V TO 5.5V) TMP35/ TMP36/ TMP37 VOUT 00337-001 SHUTDOWN Figure 1. PIN CONFIGURATIONS VOUT 1 +VS 2 NC 3 5 GND TOP VIEW (Not to Scale) 4 SHUTDOWN NC = NO CONNECT 00337-002 APPLICATIONS FUNCTIONAL BLOCK DIAGRAM Figure 2. RJ-5 (SOT-23) 8 +VS VOUT 1 7 NC TOP VIEW NC 3 (Not to Scale) 6 NC NC 2 5 SHUTDOWN GND 4 NC = NO CONNECT 00337-003 Low voltage operation (2.7 V to 5.5 V) Calibrated directly in C 10 mV/C scale factor (20 mV/C on TMP37) 2C accuracy over temperature (typ) 0.5C linearity (typ) Stable with large capacitive loads Specified -40C to +125C, operation to +150C Less than 50 A quiescent current Shutdown current 0.5 A max Low self-heating Qualified for automotive applications Figure 3. R-8 (SOIC_N) 1 2 3 BOTTOM VIEW (Not to Scale) PIN 1, +VS; PIN 2, VOUT; PIN 3, GND 00337-004 FEATURES Figure 4. T-3 (TO-92) The TMP37 is intended for applications over the range of 5C to 100C and provides an output scale factor of 20 mV/C. The TMP37 provides a 500 mV output at 25C. Operation extends to 150C with reduced accuracy for all devices when operating from a 5 V supply. The TMP35/TMP36/TMP37 are available in low cost 3-lead TO-92, 8-lead SOIC_N, and 5-lead SOT-23 surface-mount packages. Rev. F Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)1996-2010 Analog Devices, Inc. All rights reserved. TMP35/TMP36/TMP37 TABLE OF CONTENTS Features .............................................................................................. 1 Basic Temperature Sensor Connections.................................. 10 Applications....................................................................................... 1 Fahrenheit Thermometers ........................................................ 10 General Description ......................................................................... 1 Average and Differential Temperature Measurement ........... 12 Functional Block Diagram .............................................................. 1 Microprocessor Interrupt Generator....................................... 13 Pin Configurations ........................................................................... 1 Revision History ............................................................................... 2 Thermocouple Signal Conditioning with Cold-Junction Compensation............................................................................. 14 Specifications..................................................................................... 3 Using TMP3x Sensors in Remote Locations .......................... 15 Absolute Maximum Ratings............................................................ 4 Temperature to 4-20 mA Loop Transmitter .......................... 15 Thermal Resistance ...................................................................... 4 Temperature-to-Frequency Converter .................................... 16 ESD Caution.................................................................................. 4 Driving Long Cables or Heavy Capacitive Loads .................. 17 Typical Performance Characteristics ............................................. 5 Commentary on Long-Term Stability ..................................... 17 Functional Description .................................................................... 8 Outline Dimensions ....................................................................... 18 Applications Information ................................................................ 9 Ordering Guide .......................................................................... 19 Shutdown Operation.................................................................... 9 Automotive Products ................................................................. 20 Mounting Considerations ........................................................... 9 Thermal Environment Effects .................................................... 9 REVISION HISTORY 11/10--Rev. E to Rev. F 10/02--Rev. B to Rev. C Changes to Features.......................................................................... 1 Updated Outline Dimensions ....................................................... 18 Changes to Ordering Guide .......................................................... 19 Added Automotive Products Section .......................................... 20 Changes to Specifications.................................................................3 Deleted Text from Commentary on Long-Term Stability Section.............................................................................................. 13 Updated Outline Dimensions....................................................... 14 8/08--Rev. D to Rev. E 9/01--Rev. A to Rev. B Updated Outline Dimensions ....................................................... 18 Changes to Ordering Guide .......................................................... 19 Edits to Specifications .......................................................................2 Addition of New Figure 1 .................................................................2 Deletion of Wafer Test Limits Section ............................................3 3/05--Rev. C to Rev. D Updated Format..................................................................Universal Changes to Specifications ................................................................ 3 Additions to Absolute Maximum Ratings..................................... 4 Updated Outline Dimensions ....................................................... 18 Changes to Ordering Guide .......................................................... 19 6/97--Rev. 0 to Rev. A 3/96--Revision 0: Initial Version Rev. F | Page 2 of 20 TMP35/TMP36/TMP37 SPECIFICATIONS VS = 2.7 V to 5.5 V, -40C TA +125C, unless otherwise noted. Table 1. Parameter 1 ACCURACY TMP35/TMP36/TMP37 (F Grade) TMP35/TMP36/TMP37 (G Grade) TMP35/TMP36/TMP37 (F Grade) TMP35/TMP36/TMP37 (G Grade) Scale Factor, TMP35 Scale Factor, TMP36 Scale Factor, TMP37 Symbol Load Regulation Power Supply Rejection Ratio Linearity Long-Term Stability SHUTDOWN Logic High Input Voltage Logic Low Input Voltage OUTPUT TMP35 Output Voltage TMP36 Output Voltage TMP37 Output Voltage Output Voltage Range Output Load Current Short-Circuit Current Capacitive Load Driving Device Turn-On Time POWER SUPPLY Supply Range Supply Current Supply Current (Shutdown) 1 2 PSRR Test Conditions/Comments Min TA = 25C TA = 25C Over rated temperature Over rated temperature 10C TA 125C -40C TA +125C 5C TA 85C 5C TA 100C 3.0 V VS 5.5 V 0 A IL 50 A -40C TA +105C -105C TA +125C TA = 25C 3.0 V VS 5.5 V TA = 150C for 1 kHz VIH VIL VS = 2.7 V VS = 5.5 V VS ISY (ON) ISY (OFF) Max Unit 1 1 2 2 10 10 20 20 2 3 3 4 C C C C mV/C mV/C mV/C mV/C 6 25 30 50 0.5 0.4 20 60 100 mC/A mC/A mC/V mC/V C C 1.8 400 TA = 25C TA = 25C TA = 25C IL ISC CL Typ 250 750 500 10000 0.5 1 mV mV mV mV A A pF ms 0.01 5.5 50 0.5 V A A 100 0 Note 2 No oscillations 2 Output within 1C, 100 k||100 pF load2 1000 2000 50 250 2.7 Unloaded Unloaded Does not consider errors caused by self-heating. Guaranteed but not tested. Rev. F | Page 3 of 20 V mV TMP35/TMP36/TMP37 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter1, 2 Supply Voltage Shutdown Pin Output Pin Operating Temperature Range Die Junction Temperature Storage Temperature Range IR Reflow Soldering Peak Temperature Time at Peak Temperature Range Ramp-Up Rate Ramp-Down Rate Time 25C to Peak Temperature IR Reflow Soldering--Pb-Free Package Peak Temperature Time at Peak Temperature Range Ramp-Up Rate Ramp-Down Rate Time 25C to Peak Temperature Rating 7V GND SHUTDOWN +VS GND VOUT +VS -55C to +150C 175C -65C to +160C 220C (0C/5C) 10 sec to 20 sec 3C/sec -6C/sec 6 min 260C (0C) 20 sec to 40 sec 3C/sec -6C/sec 8 min Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. THERMAL RESISTANCE JA is specified for the worst-case conditions, that is, a device in socket. Table 3. Thermal Resistance Package Type TO-92 (T-3) SOIC_N (R-8) SOT-23 (RJ-5) ESD CAUTION 1 Digital inputs are protected; however, permanent damage can occur on unprotected units from high energy electrostatic fields. Keep units in conductive foam or packaging at all times until ready to use. Use proper antistatic handling procedures. 2 Remove power before inserting or removing units from their sockets. Rev. F | Page 4 of 20 JA 162 158 300 JC 120 43 180 Unit C/W C/W C/W TMP35/TMP36/TMP37 TYPICAL PERFORMANCE CHARACTERISTICS 0.4 30 20 10 0 50 TEMPERATURE (C) 100 0.3 0.2 0.1 0 -50 150 1.4 b 1.2 1.0 0.8 a 0.6 00337-007 0.4 0.2 0 -50 -25 75 100 125 31.600 c 0 25 50 TEMPERATURE (C) 75 100 POWER SUPPLY REJECTION (C/V) OUTPUT VOLTAGE (V) 1.6 25 50 TEMPERATURE (C) 100.000 a. TMP35 b. TMP36 c. TMP37 +VS = 3V 1.8 0 Figure 8. Power Supply Rejection vs. Temperature Figure 5. Load Regulation vs. Temperature (mC/A) 2.0 -25 10.000 3.160 1.000 0.320 0.100 0.032 00337-010 0 -50 +VS = 3V TO 5.5V, NO LOAD 00337-009 POWER SUPPLY REJECTION (C/V) 40 00337-005 LOAD REGULATION (mC/A) 50 0.010 20 125 100 1k FREQUENCY (Hz) 10k 100k Figure 9. Power Supply Rejection vs. Frequency Figure 6. Output Voltage vs. Temperature 5 5 4 MINIMUM SUPPLY VOLTAGE (V) a. MAXIMUM LIMIT (G GRADE) b. TYPICAL ACCURACY ERROR c. MINIMUM LIMIT (G GRADE) 1 0 -1 b -2 -3 -4 -5 c 0 20 40 60 80 100 TEMPERATURE (C) 120 MINIMUM SUPPLY VOLTAGE REQUIRED TO MEET DATA SHEET SPECIFICATION 4 NO LOAD 3 b 2 a 1 a. TMP35/TMP36 b. TMP37 0 -50 140 -25 0 25 50 TEMPERATURE (C) 00337-011 a 2 00337-008 ACCURACY ERROR (C) 3 75 100 Figure 10. Minimum Supply Voltage vs. Temperature Figure 7. Accuracy Error vs. Temperature Rev. F | Page 5 of 20 125 TMP35/TMP36/TMP37 60 400 a. +VS = 5V b. +VS = 3V 300 NO LOAD RESPONSE TIME (s) 40 a 30 00337-012 10 -50 -25 0 25 50 TEMPERATURE (C) 75 200 = +VS AND SHUTDOWN PINS LOW TO HIGH (0V TO 3V) VOUT SETTLES WITHIN 1C 100 b 20 = +VS AND SHUTDOWN PINS HIGH TO LOW (3V TO 0V) 100 00337-015 SUPPLY CURRENT (A) 50 0 -50 125 Figure 11. Supply Current vs. Temperature -25 0 25 50 TEMPERATURE (C) 75 100 125 Figure 14. VOUT Response Time for +VS Power-Up/Power-Down vs. Temperature 400 50 = SHUTDOWN PIN HIGH TO LOW (3V TO 0V) TA = 25C, NO LOAD 300 30 20 200 100 = SHUTDOWN PIN LOW TO HIGH (0V TO 3V) VOUT SETTLES WITHIN 1C 00337-013 10 0 1 2 3 4 5 SUPPLY VOLTAGE (V) 6 0 -50 8 7 75 100 125 0.8 a. +VS = 5V b. +VS = 3V TA = 25C +VS = 3V SHUTDOWN = SIGNAL 0.6 OUTPUT VOLTAGE (V) NO LOAD 30 20 a 10 0.4 0.2 0 1.0 0.8 0.6 TA = 25C +VS AND SHUTDOWN = SIGNAL 0.4 00337-014 SUPPLY CURRENT (nA) 25 50 TEMPERATURE (C) 1.0 50 b 0 -50 0 Figure 15. VOUT Response Time for SHUTDOWN Pin vs. Temperature Figure 12. Supply Current vs. Supply Voltage 40 -25 -25 0 25 50 TEMPERATURE (C) 75 100 0.2 0 125 Figure 13. Supply Current vs. Temperature (Shutdown = 0 V) 00337-017 0 00337-016 RESPONSE TIME (s) SUPPLY CURRENT (A) 40 -50 0 50 100 150 200 250 TIME (s) 300 350 400 450 Figure 16. VOUT Response Time to SHUTDOWN Pin and +VS Pin vs. Time Rev. F | Page 6 of 20 TMP35/TMP36/TMP37 110 a 10mV 100 90 90 VOLT/DIVISION 70 60 50 40 a. TMP35 SOIC SOLDERED TO 0.5" x 0.3" Cu PCB b. TMP36 SOIC SOLDERED TO 0.6" x 0.4" Cu PCB c. TMP35 TO-92 IN SOCKET SOLDERED TO 1" x 0.4" Cu PCB 00337-034 20 10 0% 10 0 00337-019 30 100 0 200 300 TIME (s) 400 500 TIME/DIVISION 600 Figure 17. Thermal Response Time in Still Air Figure 20. Temperature Sensor Wideband Output Noise Voltage; Gain = 100, BW = 157 kHz 140 2400 a. TMP35 SOIC SOLDERED TO 0.5" x 0.3" Cu PCB b. TMP36 SOIC SOLDERED TO 0.6" x 0.4" Cu PCB c. TMP35 TO-92 IN SOCKET SOLDERED TO 1" x 0.4" Cu PCB 2200 VOLTAGE NOISE DENSITY (nV/ Hz) TIME CONSTANT (s) 120 100 80 +VS = 3V, 5V 60 b 40 c 0 00337-018 20 a 0 100 200 300 400 500 AIR VELOCITY (FPM) 600 b 70 60 50 40 a. TMP35 SOIC SOLDERED TO 0.5" x 0.3" Cu PCB b. TMP36 SOIC SOLDERED TO 0.6" x 0.4" Cu PCB c. TMP35 TO-92 IN SOCKET SOLDERED TO 1" x 0.4" Cu PCB 30 20 00337-035 CHANGE (%) +VS = 3V, 5V c 10 0 0 10 20 30 TIME (s) 40 50 1400 1200 1000 800 600 a 400 a. TMP35/TMP36 b. TMP37 10 100 1k FREQUENCY (Hz) Figure 21. Voltage Noise Spectral Density vs. Frequency a 80 1600 0 700 100 90 b 1800 200 Figure 18. Thermal Response Time Constant in Forced Air 110 2000 60 Figure 19. Thermal Response Time in Stirred Oil Bath Rev. F | Page 7 of 20 00337-020 CHANGE (%) 100 +VS = 3V, 5V c b 80 1ms 10k TMP35/TMP36/TMP37 FUNCTIONAL DESCRIPTION An equivalent circuit for the TMP3x family of micropower, centigrade temperature sensors is shown in Figure 22. The core of the temperature sensor is a band gap core that comprises transistors Q1 and Q2, biased by Q3 to approximately 8 A. The band gap core operates both Q1 and Q2 at the same collector current level; however, because the emitter area of Q1 is 10 times that of Q2, the VBE of Q1 and the VBE of Q2 are not equal by the following relationship: SHUTDOWN 25A 3X Q2 1X Q4 AE,Q1 = VT x ln AE,Q2 2X R1 Q1 10X R3 Resistors R1 and R2 are used to scale this result to produce the output voltage transfer characteristic of each temperature sensor and, simultaneously, R2 and R3 are used to scale the VBE of Q1 as an offset term in VOUT. Table 4 summarizes the differences in the output characteristics of the three temperature sensors. The output voltage of the temperature sensor is available at the emitter of Q4, which buffers the band gap core and provides load current drive. The current gain of Q4, working with the available base current drive from the previous stage, sets the short-circuit current limit of these devices to 250 A. R2 VOUT 7.5A Q3 2X 6X GND 00337-006 VBE +VS Figure 22. Temperature Sensor Simplified Equivalent Circuit Table 4. TMP3x Output Characteristics Sensor TMP35 TMP36 TMP37 Rev. F | Page 8 of 20 Offset Voltage (V) 0 0.5 0 Output Voltage Scaling (mV/C) 10 10 20 Output Voltage @ 25C (mV) 250 750 500 TMP35/TMP36/TMP37 APPLICATIONS INFORMATION SHUTDOWN OPERATION THERMAL ENVIRONMENT EFFECTS All TMP3x devices include a shutdown capability, which reduces the power supply drain to less than 0.5 A maximum. This feature, available only in the SOIC_N and the SOT-23 packages, is TTL/CMOS level-compatible, provided that the temperature sensor supply voltage is equal in magnitude to the logic supply voltage. Internal to the TMP3x at the SHUTDOWN pin, a pull-up current source to +VS is connected. This allows the SHUTDOWN pin to be driven from an open-collector/drain driver. A logic low, or zero-volt condition, on the SHUTDOWN pin is required to turn off the output stage. During shutdown, the output of the temperature sensors becomes high impedance where the potential of the output pin is then determined by external circuitry. If the shutdown feature is not used, it is recommended that the SHUTDOWN pin be connected to +VS (Pin 8 on the SOIC_N; Pin 2 on the SOT-23). The thermal environment in which the TMP3x sensors are used determines two important characteristics: self-heating effects and thermal response time. Figure 23 illustrates a thermal model of the TMP3x temperature sensors, which is useful in understanding these characteristics. The shutdown response time of these temperature sensors is shown in Figure 14, Figure 15, and Figure 16. MOUNTING CONSIDERATIONS If the TMP3x temperature sensors are thermally attached and protected, they can be used in any temperature measurement application where the maximum temperature range of the medium is between -40C and +125C. Properly cemented or glued to the surface of the medium, these sensors are within 0.01C of the surface temperature. Caution should be exercised, especially with T-3 packages, because the leads and any wiring to the device can act as heat pipes, introducing errors if the surrounding air-surface interface is not isothermal. Avoiding this condition is easily achieved by dabbing the leads of the temperature sensor and the hookup wires with a bead of thermally conductive epoxy. This ensures that the TMP3x die temperature is not affected by the surrounding air temperature. Because plastic IC packaging technology is used, excessive mechanical stress should be avoided when fastening the device with a clamp or a screw-on heat tab. Thermally conductive epoxy or glue, which must be electrically nonconductive, is recommended under typical mounting conditions. These temperature sensors, as well as any associated circuitry, should be kept insulated and dry to avoid leakage and corrosion. In wet or corrosive environments, any electrically isolated metal or ceramic well can be used to shield the temperature sensors. Condensation at very cold temperatures can cause errors and should be avoided by sealing the device, using electrically nonconductive epoxy paints or dip or any one of the many printed circuit board coatings and varnishes. TJ CCH TC CC CA TA 00337-021 PD JC Figure 23. Thermal Circuit Model In the T-3 package, the thermal resistance junction-to-case, JC, is 120C/W. The thermal resistance case-to-ambient, CA, is the difference between JA and JC, and is determined by the characteristics of the thermal connection. The power dissipation of the temperature sensor, PD, is the product of the total voltage across the device and its total supply current, including any current delivered to the load. The rise in die temperature above the ambient temperature of the medium is given by TJ = PD x (JC + CA) + TA Thus, the die temperature rise of a TMP35 SOT-23 package mounted into a socket in still air at 25C and driven from a 5 V supply is less than 0.04C. The transient response of the TMP3x sensors to a step change in the temperature is determined by the thermal resistances and the thermal capacities of the die, CCH, and the case, CC. The thermal capacity of CC varies with the measurement medium because it includes anything in direct contact with the package. In all practical cases, the thermal capacity of CC is the limiting factor in the thermal response time of the sensor and can be represented by a single-pole RC time constant response. Figure 17 and Figure 19 show the thermal response time of the TMP3x sensors under various conditions. The thermal time constant of a temperature sensor is defined as the time required for the sensor to reach 63.2% of the final value for a step change in the temperature. For example, the thermal time constant of a TMP35 SOIC package sensor mounted onto a 0.5" x 0.3" PCB is less than 50 sec in air, whereas in a stirred oil bath, the time constant is less than 3 sec. Rev. F | Page 9 of 20 TMP35/TMP36/TMP37 BASIC TEMPERATURE SENSOR CONNECTIONS FAHRENHEIT THERMOMETERS Figure 24 illustrates the basic circuit configuration for the TMP3x family of temperature sensors. The table in Figure 24 shows the pin assignments of the temperature sensors for the three package types. For the SOT-23, Pin 3 is labeled NC, as are Pin 2, Pin 3, Pin 6, and Pin 7 on the SOIC_N package. It is recommended that no electrical connections be made to these pins. If the shutdown feature is not needed on the SOT-23 or on the SOIC_N package, the SHUTDOWN pin should be connected to +VS. Although the TMP3x temperature sensors are centigrade temperature sensors, a few components can be used to convert the output voltage and transfer characteristics to directly read Fahrenheit temperatures. Figure 25 shows an example of a simple Fahrenheit thermometer using either the TMP35 or the TMP37. Using the TMP35, this circuit can be used to sense temperatures from 41F to 257F with an output transfer characteristic of 1 mV/F; using the TMP37, this circuit can be used to sense temperatures from 41F to 212F with an output transfer characteristic of 2 mV/F. This particular approach does not lend itself to the TMP36 because of its inherent 0.5 V output offset. The circuit is constructed with an AD589, a 1.23 V voltage reference, and four resistors whose values for each sensor are shown in the table in Figure 25. The scaling of the output resistance levels ensures minimum output loading on the temperature sensors. A generalized expression for the transfer equation of the circuit is given by 2.7V < +VS < 5.5V 0.1F +VS VOUT GND R1 (TMP35 ) + R3 ( AD589 ) VOUT = R1 + R2 R3 + R4 +VS GND VOUT SHUTDOWN SOIC_N 8 4 1 5 SOT-23 TO-92 2 1 5 3 1 2 4 NA PACKAGE 00337-022 PIN ASSIGNMENTS Figure 24. Basic Temperature Sensor Circuit Configuration Note the 0.1 F bypass capacitor on the input. This capacitor should be a ceramic type, have very short leads (surface-mount is preferable), and be located as close as possible in physical proximity to the temperature sensor supply pin. Because these temperature sensors operate on very little supply current and may be exposed to very hostile electrical environments, it is important to minimize the effects of radio frequency interference (RFI) on these devices. The effect of RFI on these temperature sensors specifically and on analog ICs in general is manifested as abnormal dc shifts in the output voltage due to the rectification of the high frequency ambient noise by the IC. When the devices are operated in the presence of high frequency radiated or conducted noise, a large value tantalum capacitor (2.2 F) placed across the 0.1 F ceramic capacitor may offer additional noise immunity. where: TMP35 is the output voltage of the TMP35 or the TMP37 at the measurement temperature, TM. AD589 is the output voltage of the reference, that is, 1.23 V. The output voltage of this circuit is not referenced to the circuit's common ground. If this output voltage were applied directly to the input of an ADC, the ADC common ground should be adjusted accordingly. +VS 0.1F +VS TMP35/ TMP37 VOUT R1 GND + R2 VOUT AD589 1.23V R3 - R4 SENSOR TCVOUT R1 (k) R2 (k) R3 (k) R4 (k) TMP35 TMP37 1mV/F 2mV/F 45.3 45.3 10 10 10 10 374 182 Figure 25. TMP35/TMP37 Fahrenheit Thermometers Rev. F | Page 10 of 20 00337-023 TMP3x SHUTDOWN TMP35/TMP36/TMP37 At the expense of additional circuitry, the offset produced by the circuit in Figure 26 can be avoided by using the circuit in Figure 27. In this circuit, the output of the TMP36 is conditioned by a single-supply, micropower op amp, the OP193. Although the entire circuit operates from a single 3 V supply, the output voltage of the circuit reads the temperature directly, with a transfer characteristic of 1 mV/F, without offset. This is accomplished through an ADM660, which is a supply voltage inverter. The 3 V supply is inverted and applied to the V- terminal of the OP193. Thus, for a temperature range between -40F and +257F, the output of the circuit reads -40 mV to +257 mV. A general expression for the transfer equation of the circuit is given by The same circuit principles can be applied to the TMP36, but because of the inherent offset of the TMP36, the circuit uses only two resistors, as shown in Figure 26. In this circuit, the output voltage transfer characteristic is 1 mV/F but is referenced to the common ground of the circuit; however, there is a 58 mV (58F) offset in the output voltage. For example, the output voltage of the circuit reads 18 mV if the TMP36 is placed in a -40F ambient environment and 315 mV at +257F. +VS +VS VOUT R6 1 + R4 (TMP36 ) - R4 VS VOUT = R5 + R6 R3 R3 2 R1 45.3k GND R2 10k VOUT @ 1mV/F - 58F 00337-024 TMP36 0.1F VOUT @ -40F = 18mV VOUT @ +257F = 315mV Figure 26. TMP36 Fahrenheit Thermometer Version 1 +3V R1 50k R3 R4 C1 + 10F R2 50k 0.1F 7 2 +VS VOUT TMP36 R5 3 + 6 VOUT @ 1mV/F -40F TA +257F 4 R6 GND OP193 8 NC ELEMENT VALUE R3 258.6k R4 10k R5 47.7k R6 10k 1 5 2 10F ADM660 + 6 -3V + 10F 4 3 7 NC 00337-025 10F/0.1F + - Figure 27. TMP36 Fahrenheit Thermometer Version 2 Rev. F | Page 11 of 20 TMP35/TMP36/TMP37 2.7V < +VS < 5.5V AVERAGE AND DIFFERENTIAL TEMPERATURE MEASUREMENT 0.1F In Figure 28, an OP193 sums the outputs of three temperature sensors to produce an output voltage scaled by 10 mV/C that represents the average temperature at three locations. The circuit can be extended to include as many temperature sensors as required as long as the transfer equation of the circuit is maintained. In this application, it is recommended that one temperature sensor type be used throughout the circuit; otherwise, the output voltage of the circuit cannot produce an accurate reading of the various ambient conditions. The circuit in Figure 29 illustrates how a pair of TMP3x sensors used with an OP193 configured as a difference amplifier can read the difference in temperature between two locations. In these applications, it is always possible that one temperature sensor is reading a temperature below that of the other sensor. To accommodate this condition, the output of the OP193 is offset to a voltage at one-half the supply via R5 and R6. Thus, the output voltage of the circuit is measured relative to this point, as shown in Figure 29. Using the TMP36, the output voltage of the circuit is scaled by 10 mV/C. To minimize the error in the difference between the two measured temperatures, a common, readily available thin-film resistor network is used for R1 to R4. 2 3 TMP3x TMP3x VTEMP(AVG) @ 10mV/C FOR TMP35/TMP36 @ 20mV/C FOR TMP37 7 - OP193 + 6 4 R5 100k R1 300k R6 7.5k R2 300k FOR R1 = R2 = R3 = R; TMP3x R3 300k R4 7.5k VTEMP(AVG) = 1 (TMP3x1 + TMP3x2 + TMP3x3) 3 R5 = R1 3 R4 = R6 00337-026 In many commercial and industrial environments, temperature sensors often measure the average temperature in a building, or the difference in temperature between two locations on a factory floor or in an industrial process. The circuits in Figure 28 and Figure 29 demonstrate an inexpensive approach to average and differential temperature measurement. Figure 28. Configuring Multiple Sensors for Average Temperature Measurements 2.7V < +VS < 5.5V 0.1F TMP36 @ T1 R11 R21 R8 25k 0.1F 7 2 0.1F TMP36 R31 - OP193 3 @ T2 + 6 VOUT 4 R7 100k R9 25k CENTERED AT 0C TA 125C R5 100k 1F R6 100k VOUT = T2 - T1 @ 10mV/C VS CENTERED AT 2 NOTE: 1 R1-R4, CADDOCK T914-100k-100, OR EQUIVALENT. Figure 29. Configuring Multiple Sensors for Differential Temperature Measurements Rev. F | Page 12 of 20 00337-027 R41 TMP35/TMP36/TMP37 Because temperature is a slowly moving quantity, the possibility for comparator chatter exists. To avoid this condition, hysteresis is used around the comparator. In this application, a hysteresis of 5C about the trip point was arbitrarily chosen; the ultimate value for hysteresis should be determined by the end application. The output logic voltage swing of the comparator with R1 and R2 determines the amount of comparator hysteresis. Using a 3.3 V supply, the output logic voltage swing of the CMP402 is 2.6 V; therefore, for a hysteresis of 5C (50 mV @ 10 mV/C), R1 is set to 20 k, and R2 is set to 1 M. An expression for the hysteresis of this circuit is given by MICROPROCESSOR INTERRUPT GENERATOR These inexpensive temperature sensors can be used with a voltage reference and an analog comparator to configure an interrupt generator for microprocessor applications. With the popularity of fast microprocessors, the need to indicate a microprocessor overtemperature condition has grown tremendously. The circuit in Figure 30 demonstrates one way to generate an interrupt using a TMP35, a CMP402 analog comparator, and a REF191, a 2 V precision voltage reference. The circuit is designed to produce a logic high interrupt signal if the microprocessor temperature exceeds 80C. This 80C trip point was arbitrarily chosen (final value set by the microprocessor thermal reference design) and is set using an R3 to R4 voltage divider of the REF191 output voltage. Because the output of the TMP35 is scaled by 10 mV/C, the voltage at the inverting terminal of the CMP402 is set to 0.8 V. ( R1 VHYS = VLOGIC SWING, CMP402 R2 ) Because this circuit is probably used in close proximity to high speed digital circuits, R1 is split into equal values and a 1000 pF capacitor is used to form a low-pass filter on the output of the TMP35. Furthermore, to prevent high frequency noise from contaminating the comparator trip point, a 0.1 F capacitor is used across R4. 3.3V R2 1M +VS TMP35 VOUT 6 CL 1000pF R5 100k GND 3 R1B 10k 5 4 - CMP402 + 2 INTERRUPT 14 0.1F 13 2 3 REF191 R3 16k 6 + 4 1F >80C <80C VREF R4 10k 0.1F C1 = 1 CMP402 4 Figure 30. Microprocessor Overtemperature Interrupt Generator Rev. F | Page 13 of 20 00337-028 0.1F 0.1F R1A 10k TMP35/TMP36/TMP37 and the wires of the thermocouple from introducing an error in the measured temperature. This compensation works extremely well for circuit ambient temperatures in the range of 20C to 50C. Over a 250C measurement temperature range, the thermocouple produces an output voltage change of 10.151 mV. Because the required output full-scale voltage of the circuit is 2.5 V, the gain of the circuit is set to 246.3. Choosing R4 equal to 4.99 k sets R5 equal to 1.22 M. Because the closest 1% value for R5 is 1.21 M, a 50 k potentiometer is used with R5 for fine trim of the full-scale output voltage. Although the OP193 is a superior single-supply, micropower operational amplifier, its output stage is not rail-to-rail; therefore, the 0C output voltage level is 0.1 V. If this circuit is digitized by a single-supply ADC, the ADC common should be adjusted to 0.1 V accordingly. THERMOCOUPLE SIGNAL CONDITIONING WITH COLD-JUNCTION COMPENSATION The circuit in Figure 31 conditions the output of a Type K thermocouple, while providing cold-junction compensation for temperatures between 0C and 250C. The circuit operates from a single 3.3 V to 5.5 V supply and is designed to produce an output voltage transfer characteristic of 10 mV/C. A Type K thermocouple exhibits a Seebeck coefficient of approximately 41 V/C; therefore, at the cold junction, the TMP35, with a temperature coefficient of 10 mV/C, is used with R1 and R2 to introduce an opposing cold-junction temperature coefficient of -41 V/C. This prevents the isothermal, cold-junction connection between the PCB tracks of the circuit 3.3V < +VS < 5.5V +VS TMP35 R11 24.9k COLD JUNCTION ALUMEL - 0C TA 250C ISOTHERMAL BLOCK R51 1.21M 7 2 - OP193 CU 3 + TYPE K THERMOCOUPLE R4 4.99k 0.1F GND CHROMEL P1 50k CU + 6 4 R6 100k 5% VOUT 0V TO 2.5V NOTE: 1 ALL RESISTORS 1% UNLESS OTHERWISE NOTED. R21 102 Figure 31. Single-Supply, Type K Thermocouple Signal Conditioning Circuit with Cold-Junction Compensation Rev. F | Page 14 of 20 00337-029 0.1F R3 10M 5% VOUT TMP35/TMP36/TMP37 USING TMP3x SENSORS IN REMOTE LOCATIONS TEMPERATURE TO 4-20 mA LOOP TRANSMITTER In many industrial environments, sensors are required to operate in the presence of high ambient noise. These noise sources take many forms, for example, SCR transients, relays, radio transmitters, arc welders, and ac motors. They can also be used at considerable distances from the signal conditioning circuitry. These high noise environments are typically in the form of electric fields, so the voltage output of the temperature sensor can be susceptible to contamination from these noise sources. In many process control applications, 2-wire transmitters are used to convey analog signals through noisy ambient environments. These current transmitters use a zero-scale signal current of 4 mA, which can be used to power the signal conditioning circuitry of the transmitter. The full-scale output signal in these transmitters is 20 mA. Figure 32 illustrates a way to convert the output voltage of a TMP3x sensor into a current to be transmitted down a long twisted pair shielded cable to a ground referenced receiver. The temperature sensors are not capable of high output current operation; thus, a standard PNP transistor is used to boost the output current drive of the circuit. As shown in the table in Figure 32, the values of R2 and R3 were chosen to produce an arbitrary full-scale output current of 2 mA. Lower values for the full-scale current are not recommended. The minimum-scale output current produced by the circuit could be contaminated by ambient magnetic fields operating in the near vicinity of the circuit/cable pair. Because the circuit uses an external transistor, the minimum recommended operating voltage for this circuit is 5 V. To minimize the effects of EMI (or RFI), both the circuit and the temperature sensor supply pins are bypassed with good quality ceramic capacitors. R1 4.7k 5V 2N2907 VOUT +VS 0.1F 0.01F TMP3x GND VOUT R3 R2 SENSOR R2 R3 TMP35 634 634 TMP36 887 887 TMP37 1k 1k 00337-030 TWISTED PAIR BELDEN TYPE 9502 OR EQUIVALENT Figure 32. Remote, 2-Wire Boosted Output Current Temperature Sensor Figure 33 illustrates a circuit that transmits temperature information in this fashion. Using a TMP3x as the temperature sensor, the output current is linearly proportional to the temperature of the medium. The entire circuit operates from the 3 V output of the REF193. The REF193 requires no external trimming because of its tight initial output voltage tolerance and the low supply current of the TMP3x, the OP193, and the REF193. The entire circuit consumes less than 3 mA from a total budget of 4 mA. The OP193 regulates the output current to satisfy the current summation at the noninverting node of the OP193. A generalized expression for the KCL equation at Pin 3 of the OP193 is given by 1 TMP3x x R3 VREF x R3 I OUT = + x R1 R2 R7 For each temperature sensor, Table 5 provides the values for the components P1, P2, and R1 to R4. Table 5. Circuit Element Values for Loop Transmitter Sensor TMP35 TMP36 TMP37 R1 97.6 k 97.6 k 97.6 k P1 5 k 5 k 5 k R2 1.58 M 931 k 10.5 k P2 100 k 50 k 500 R3 140 k 97.6 k 84.5 k R4 56.2 k 47 k 8.45 k The 4 mA offset trim is provided by P2, and P1 provides the full-scale gain trim of the circuit at 20 mA. These two trims do not interact because the noninverting input of the OP193 is held at a virtual ground. The zero-scale and full-scale output currents of the circuit are adjusted according to the operating temperature range of each temperature sensor. The Schottky diode, D1, is required in this circuit to prevent loop supply power-on transients from pulling the noninverting input of the OP193 more than 300 mV below its inverting input. Without this diode, such transients can cause phase reversal of the operational amplifier and possible latch-up of the transmitter. The loop supply voltage compliance of the circuit is limited by the maximum applied input voltage to the REF193; it is from 9 V to 18 V. Rev. F | Page 15 of 20 TMP35/TMP36/TMP37 3V + R21 P21 4mA ADJUST R11 TMP3x VOUT GND 1F 2 4 VLOOP 9V TO 18V 0.1F 2 P11 20mA ADJUST REF193 3 7 - OP193 R6 100k 6 Q1 2N1711 + VOUT 4 D1 R31 NOTE: 1 SEE TEXT FOR VALUES. R5 100k R41 RL 250 R7 100 D1: HP5082-2810 00337-032 +VS 6 IL Figure 33. Temperature to 4-20 mA Loop Transmitter TEMPERATURE-TO-FREQUENCY CONVERTER 5V RPU 5k +VS 8 10F/0.1F The circuit in Figure 34 illustrates a method by which the outputs of these temperature sensors can be converted to a frequency using the AD654. The output signal of the AD654 is a square wave that is proportional to the dc input voltage across Pin 4 and Pin 3. The transfer equation of the circuit is given by V - VOFFSET f OUT = TPM 10 x (RT x CT ) CT1 0.1F VOUT TMP3x 6 7 4 AD654 3 1 GND RT1 5V P2 100k 2 5 R1 NB: ATTA (MIN), fOUT = 0Hz P1 ROFF1 470 fOUT OFFSET NOTE: 1R AND C - SEE TABLE T T ROFF2 10 SENSOR RT (R1 + P1) CT TMP35 TMP36 TMP37 11.8k + 500 16.2k + 500 18.2k + 1k 1.7nF 1.8nF 2.1nF Figure 34. Temperature-to-Frequency Converter Rev. F | Page 16 of 20 fOUT 00337-031 Another common method of transmitting analog information from a remote location is to convert a voltage to an equivalent value in the frequency domain. This is readily done with any of the low cost, monolithic voltage-to-frequency converters (VFCs) available. These VFCs feature a robust, open-collector output transistor for easy interfacing to digital circuitry. The digital signal produced by the VFC is less susceptible to contamination from external noise sources and line voltage drops because the only important information is the frequency of the digital signal. When the conversions between temperature and frequency are done accurately, the temperature data from the sensors can be reliably transmitted. TMP35/TMP36/TMP37 An offset trim network (fOUT OFFSET ) is included with this circuit to set fOUT to 0 Hz when the minimum output voltage of the temperature sensor is reached. Potentiometer P1 is required to calibrate the absolute accuracy of the AD654. The table in Figure 34 illustrates the circuit element values for each of the three sensors. The nominal offset voltage required for 0 Hz output from the TMP35 is 50 mV; for the TMP36 and TMP37, the offset voltage required is 100 mV. For the circuit values shown, the output frequency transfer characteristic of the circuit was set at 50 Hz/C in all cases. At the receiving end, a frequency-to-voltage converter (FVC) can be used to convert the frequency back to a dc voltage for further processing. One such FVC is the AD650. For complete information about the AD650 and the AD654, consult the individual data sheets for those devices. COMMENTARY ON LONG-TERM STABILITY The concept of long-term stability has been used for many years to describe the amount of parameter shift that occurs during the lifetime of an IC. This is a concept that has been typically applied to both voltage references and monolithic temperature sensors. Unfortunately, integrated circuits cannot be evaluated at room temperature (25C) for 10 years or more to determine this shift. As a result, manufacturers very typically perform accelerated lifetime testing of integrated circuits by operating ICs at elevated temperatures (between 125C and 150C) over a shorter period of time (typically, between 500 and 1000 hours). As a result of this operation, the lifetime of an integrated circuit is significantly accelerated due to the increase in rates of reaction within the semiconductor material. DRIVING LONG CABLES OR HEAVY CAPACITIVE LOADS Although the TMP3x family of temperature sensors can drive capacitive loads up to 10,000 pF without oscillation, output voltage transient response times can be improved by using a small resistor in series with the output of the temperature sensor, as shown in Figure 35. As an added benefit, this resistor forms a low-pass filter with the cable capacitance, which helps to reduce bandwidth noise. Because the temperature sensor is likely to be used in environments where the ambient noise level can be very high, this resistor helps to prevent rectification by the devices of the high frequency noise. The combination of this resistor and the supply bypass capacitor offers the best protection. +VS TMP3x VOUT 750 LONG CABLE OR HEAVY CAPACITIVE LOADS GND 00337-033 0.1F Figure 35. Driving Long Cables or Heavy Capacitive Loads Rev. F | Page 17 of 20 TMP35/TMP36/TMP37 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 5 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE 6.20 (0.2441) 5.80 (0.2284) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) 5 1.70 1.60 1.50 0.50 (0.0196) 0.25 (0.0099) 1 4 2 3.00 2.80 2.60 3 45 8 0 0.95 BSC 0.25 (0.0098) 0.17 (0.0067) 1.90 BSC 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-012-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. 1.30 1.15 0.90 1.45 MAX 0.95 MIN 0.15 MAX 0.05 MIN 0.50 MAX 0.35 MIN 0.20 MAX 0.08 MIN 10 5 0 SEATING PLANE 0.60 BSC COMPLIANT TO JEDEC STANDARDS MO-178-AA Figure 36. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 0.210 (5.33) 0.190 (4.83) 0.170 (4.32) Figure 37. 5-Lead Small Outline Transistor Package [SOT-23] (RJ-5) Dimensions shown in millimeters 0.0220 (0.56) 0.0185 (0.47) 0.0150 (0.38) 0.205 (5.21) 0.190 (4.83) 0.175 (4.45) 0.165 (4.19) 0.145 (3.68) 0.125 (3.18) 0.1150 (2.92) 0.0975 (2.48) 0.0800 (2.03) 0.055 (1.40) 0.050 (1.27) 0.045 (1.15) 3 2 0.500 (12.70) MIN SEATING PLANE 1 0.020 (0.51) 0.017 (0.43) 0.014 (0.36) BOTTOM VIEW COMPLIANT TO JEDEC STANDARDS TO-226-AA CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 38. 3-Pin Plastic Header-Style Package [TO-92] (T-3) Dimensions shown in inches and (millimeters) Rev. F | Page 18 of 20 042208-A FRONT VIEW 0.105 (2.68) 0.100 (2.54) 0.095 (2.42) 0.55 0.45 0.35 11-01-2010-A 8 1 012407-A 4.00 (0.1574) 3.80 (0.1497) 3.00 2.90 2.80 TMP35/TMP36/TMP37 ORDERING GUIDE Model1, 2 TMP35FSZ-REEL TMP35GRT-REEL7 TMP35GRTZ-REEL7 TMP35GS TMP35GT9 TMP35GT9Z ADW75001Z-0REEL7 TMP36FS TMP36FS-REEL TMP36FSZ TMP36FSZ-REEL TMP36GRT-REEL7 TMP36GRTZ-REEL7 TMP36GS TMP36GS-REEL TMP36GS-REEL7 TMP36GSZ TMP36GSZ-REEL TMP36GSZ-REEL7 TMP36GT9 TMP36GT9Z TMP37FT9 TMP37FT9-REEL TMP37FT9Z TMP37GRT-REEL7 TMP37GRTZ-REEL7 TMP37GSZ TMP37GSZ-REEL TMP37GT9 TMP37GT9-REEL TMP37GT9Z 1 2 Accuracy at 25C (C max) 2.0 3.0 3.0 3.0 3.0 3.0 3.0 2.0 2.0 2.0 2.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 2.0 2.0 2.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Linear Operating Temperature Range 10C to 125C 10C to 125C 10C to 125C 10C to 125C 10C to 125C 10C to 125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C 5C to 100C 5C to 100C 5C to 100C 5C to 100C 5C to 100C 5C to 100C 5C to 100C 5C to 100C 5C to 100C 5C to 100C Package Description 8-Lead Standard Small Outline Package (SOIC_N) 5-Lead Small Outline Transistor Package (SOT-23) 5-Lead Small Outline Transistor Package (SOT-23) 8-Lead Standard Small Outline Package (SOIC_N) 3-Pin Plastic Header-Style Package (TO-92) 3-Pin Plastic Header-Style Package (TO-92) 5-Lead Small Outline Transistor Package (SOT-23) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 5-Lead Small Outline Transistor Package (SOT-23) 5-Lead Small Outline Transistor Package (SOT-23) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 3-Pin Plastic Header-Style Package (TO-92) 3-Pin Plastic Header-Style Package (TO-92) 3-Pin Plastic Header-Style Package (TO-92) 3-Pin Plastic Header-Style Package (TO-92) 3-Pin Plastic Header-Style Package (TO-92) 5-Lead Small Outline Transistor Package (SOT-23) 5-Lead Small Outline Transistor Package (SOT-23) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 3-Pin Plastic Header-Style Package (TO-92) 3-Pin Plastic Header-Style Package (TO-92) 3-Pin Plastic Header-Style Package (TO-92) Z = RoHS Compliant Part. W = Qualified for Automotive Applications. Rev. F | Page 19 of 20 Package Option R-8 RJ-5 RJ-5 R-8 T-3 T-3 RJ-5 R-8 R-8 R-8 R-8 RJ-5 RJ-5 R-8 R-8 R-8 R-8 R-8 R-8 T-3 T-3 T-3 T-3 T-3 RJ-5 RJ-5 R-8 R-8 T-3 T-3 T-3 Branding T5G #T11 #T6G T6G #T6G T7G #T12 TMP35/TMP36/TMP37 AUTOMOTIVE PRODUCTS The ADW75001Z-0REEL7 model is available with controlled manufacturing to support the quality and reliability requirements of automotive applications. Note that this automotive model may have specifications that differ from the commercial models; therefore, designers should review the Specifications section of this data sheet carefully. Only automotive grade products shown are available for use in automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for these models. (c)1996-2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D00337-0-11/10(F) Rev. F | Page 20 of 20