Low Voltage Temperature Sensors TMP35/TMP36/TMP37

Transcription

1 Low Voltage Temperature Sensors TMP5/TMP6/TMP7 FEATURES Low voltage operation (.7 V to 5.5 V) Calibrated directly in C mv/ C scale factor ( mv/ C on TMP7) ± C accuracy over temperature (typ) ±.5 C linearity (typ) Stable with large capacitive loads Specified C to 5 C, operation to 5 C Less than 5 μa quiescent current Shutdown current.5 μa max Low self-heating Qualified for automotive applications APPLICATIONS Environmental control systems Thermal protection Industrial process control Fire alarms Power system monitors CPU thermal management GENERAL DESCRIPTION The TMP5/TMP6/TMP7 are low voltage, precision centigrade temperature sensors. They provide a voltage output that is linearly proportional to the Celsius (centigrade) temperature. The TMP5/ TMP6/TMP7 do not require any external calibration to provide typical accuracies of ± C at 5 C and ± C over the C to 5 C temperature range. The low output impedance of the TMP5/TMP6/TMP7 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.7 V to 5.5 V maximum. The supply current runs well below 5 μa, providing very low self-heating less than. C in still air. In addition, a shutdown function is provided to cut the supply current to less than.5 μa. The TMP5 is functionally compatible with the LM5/LM5 and provides a 5 mv output at 5 C. The TMP5 reads temperatures from C to 5 C. The TMP6 is specified from C to 5 C, provides a 75 mv output at 5 C, and operates to 5 C from a single.7 V supply. The TMP6 is functionally compatible with the LM5. Both the TMP5 and TMP6 have an output scale factor of mv/ C. FUNCTIONAL BLOCK DIAGRAM SHUTDOWN V S V S (.7V TO 5.5V) TMP5/ TMP6/ TMP7 Figure. PIN CONFIGURATIONS NC NC NC TOP VIEW (Not to Scale) 5 NC = NO CONNECT SHUTDOWN Figure. RJ-5 (SOT-) TOP VIEW (Not to Scale) NC = NO CONNECT 8 V S 7 NC 6 NC 5 SHUTDOWN Figure. R-8 (SOIC_N) BOTTOM VIEW (Not to Scale) PIN, V S ; PIN, ; PIN, Figure. T- (TO-9) The TMP7 is intended for applications over the range of 5 C to C and provides an output scale factor of mv/ C. The TMP7 provides a 5 mv output at 5 C. Operation extends to 5 C with reduced accuracy for all devices when operating from a 5 V supply. The TMP5/TMP6/TMP7 are available in low cost -lead TO-9, 8-lead SOIC_N, and 5-lead SOT- 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 96, Norwood, MA 6-96, U.S.A. Tel: Fax: Analog Devices, Inc. All rights reserved.

2 TABLE OF CONTENTS Features... Applications... General Description... Functional Block Diagram... Pin Configurations... Revision History... Specifications... Absolute Maximum Ratings... Thermal Resistance... ESD Caution... Typical Performance Characteristics... 5 Functional Description... 8 Applications Information... 9 Shutdown Operation... 9 Mounting Considerations... 9 Thermal Environment Effects... 9 Basic Temperature Sensor Connections... Fahrenheit Thermometers... Average and Differential Temperature Measurement... Microprocessor Interrupt Generator... Thermocouple Signal Conditioning with Cold-Junction Compensation... Using TMPx Sensors in Remote Locations... 5 Temperature to ma Loop Transmitter... 5 Temperature-to-Frequency Converter... 6 Driving Long Cables or Heavy Capacitive Loads... 7 Commentary on Long-Term Stability... 7 Outline Dimensions... 8 Ordering Guide... 9 Automotive Products... REVISION HISTORY / Rev. E to Rev. F Changes to Features... Updated Outline Dimensions... 8 Changes to Ordering Guide... 9 Added Automotive Products Section... 8/8 Rev. D to Rev. E Updated Outline Dimensions... 8 Changes to Ordering Guide... 9 /5 Rev. C to Rev. D Updated Format...Universal Changes to Specifications... Additions to Absolute Maximum Ratings... Updated Outline Dimensions... 8 Changes to Ordering Guide... 9 / Rev. B to Rev. C Changes to Specifications... Deleted Text from Commentary on Long-Term Stability Section... Updated Outline Dimensions... 9/ Rev. A to Rev. B Edits to Specifications... Addition of New Figure... Deletion of Wafer Test Limits Section... 6/97 Rev. to Rev. A /96 Revision : Initial Version Rev. F Page of

3 SPECIFICATIONS VS =.7 V to 5.5 V, C TA 5 C, unless otherwise noted. Table. Parameter Symbol Test Conditions/Comments Min Typ Max Unit ACCURACY TMP5/TMP6/TMP7 (F Grade) TA = 5 C ± ± C TMP5/TMP6/TMP7 (G Grade) TA = 5 C ± ± C TMP5/TMP6/TMP7 (F Grade) Over rated temperature ± ± C TMP5/TMP6/TMP7 (G Grade) Over rated temperature ± ± C Scale Factor, TMP5 C TA 5 C mv/ C Scale Factor, TMP6 C TA 5 C mv/ C Scale Factor, TMP7 5 C TA 85 C mv/ C 5 C TA C mv/ C. V VS 5.5 V Load Regulation μa IL 5 μa C TA 5 C 6 m C/μA 5 C TA 5 C 5 6 m C/μA Power Supply Rejection Ratio PSRR TA = 5 C m C/V. V VS 5.5 V 5 m C/V Linearity.5 C Long-Term Stability TA = 5 C for khz. C SHUTDOWN Logic High Input Voltage VIH VS =.7 V.8 V Logic Low Input Voltage VIL VS = 5.5 V mv OUTPUT TMP5 Output Voltage TA = 5 C 5 mv TMP6 Output Voltage TA = 5 C 75 mv TMP7 Output Voltage TA = 5 C 5 mv Output Voltage Range mv Output Load Current IL 5 μa Short-Circuit Current ISC Note 5 μa Capacitive Load Driving CL No oscillations pf Device Turn-On Time Output within ± C, kω pf load.5 ms POWER SUPPLY Supply Range VS V Supply Current ISY (ON) Unloaded 5 μa Supply Current (Shutdown) ISY (OFF) Unloaded..5 μa Does not consider errors caused by self-heating. Guaranteed but not tested. Rev. F Page of

4 ABSOLUTE MAXIMUM RATINGS Table. Parameter, Rating Supply Voltage 7 V Shutdown Pin SHUTDOWN VS Output Pin VOUT VS Operating Temperature Range 55 C to 5 C Die Junction Temperature 75 C Storage Temperature Range 65 C to 6 C IR Reflow Soldering Peak Temperature C ( C/5 C) Time at Peak Temperature Range sec to sec Ramp-Up Rate C/sec Ramp-Down Rate 6 C/sec Time 5 C to Peak Temperature 6 min IR Reflow Soldering Pb-Free Package Peak Temperature 6 C ( C) Time at Peak Temperature Range sec to sec Ramp-Up Rate C/sec Ramp-Down Rate 6 C/sec Time 5 C to Peak Temperature 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 θja is specified for the worst-case conditions, that is, a device in socket. Table. Thermal Resistance Package Type θja θjc Unit TO-9 (T-) 6 C/W SOIC_N (R-8) 58 C/W SOT- (RJ-5) 8 C/W ESD CAUTION 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. Remove power before inserting or removing units from their sockets. Rev. F Page of

5 TYPICAL PERFORMANCE CHARACTERISTICS 5. LOAD REGULATION (m C/µA) POWER SUPPLY REJECTION ( C/V)... V S = V TO 5.5V, NO LOAD TEMPERATURE ( C) Figure 5. Load Regulation vs. Temperature (m C/μA) TEMPERATURE ( C) Figure 8. Power Supply Rejection vs. Temperature 7-9 OUTPUT VOLTAGE (V) a. TMP5 b. TMP6 c. TMP7 V S = V TEMPERATURE ( C) Figure 6. Output Voltage vs. Temperature c a b 7-7 POWER SUPPLY REJECTION ( C/V) k k k FREQUENCY (Hz) Figure 9. Power Supply Rejection vs. Frequency ACCURACY ERROR ( C) a b a. MAXIMUM LIMIT (G GRADE) b. TYPICAL ACCURACY ERROR c. MINIMUM LIMIT (G GRADE) c TEMPERATURE ( C) 7-8 MINIMUM SUPPLY VOLTAGE (V) MINIMUM SUPPLY VOLTAGE REQUIRED TO MEET DATA SHEET SPECIFICATION NO LOAD a. TMP5/TMP6 b. TMP TEMPERATURE ( C) a b 7- Figure 7. Accuracy Error vs. Temperature Figure. Minimum Supply Voltage vs. Temperature Rev. F Page 5 of

6 6 a. V S = 5V b. V S = V SUPPLY CURRENT (µa) 5 NO LOAD a b RESPONSE TIME (µs) = V S AND SHUTDOWN PINS HIGH TO LOW (V TO V) = V S AND SHUTDOWN PINS LOW TO HIGH (V TO V) SETTLES WITHIN ± C TEMPERATURE ( C) Figure. Supply Current vs. Temperature TEMPERATURE ( C) Figure. VOUT Response Time for VS Power-Up/Power-Down vs. Temperature T A = 5 C, NO LOAD = SHUTDOWN PIN HIGH TO LOW (V TO V) SUPPLY CURRENT (μa) SUPPLY VOLTAGE (V) 8 7- RESPONSE TIME (µs) = SHUTDOWN PIN LOW TO HIGH (V TO V) SETTLES WITHIN ± C TEMPERATURE ( C) 7-6 Figure. Supply Current vs. Supply Voltage Figure 5. VOUT Response Time for SHUTDOWN Pin vs. Temperature 5. SUPPLY CURRENT (na) a. V S = 5V b. V S = V NO LOAD TEMPERATURE ( C) Figure. Supply Current vs. Temperature (Shutdown = V) a b 7- OUTPUT VOLTAGE (V) T A = 5 C V S = V SHUTDOWN = SIGNAL T A = 5 C V S AND SHUTDOWN = SIGNAL TIME (µs) Figure 6. VOUT Response Time to SHUTDOWN Pin and VS Pin vs. Time 7-7 Rev. F Page 6 of

7 a mv ms 9 8 b c V S = V, 5V 9 CHANGE (%) a. TMP5 SOIC SOLDERED TO.5"." Cu PCB b. TMP6 SOIC SOLDERED TO.6"." Cu PCB c. TMP5 TO-9 IN SOCKET SOLDERED TO "." Cu PCB VOLT/DIVISION % 5 6 TIME (s) 7- TIME/DIVISION 7-9 Figure 7. Thermal Response Time in Still Air Figure. Temperature Sensor Wideband Output Noise Voltage; Gain =, BW = 57 khz TIME CONSTANT (s) 8 6 a. TMP5 SOIC SOLDERED TO.5"." Cu PCB b. TMP6 SOIC SOLDERED TO.6"." Cu PCB c. TMP5 TO-9 IN SOCKET SOLDERED TO "." Cu PCB b V S = V, 5V a 5 6 AIR VELOCITY (FPM) Figure 8. Thermal Response Time Constant in Forced Air c VOLTAGE NOISE DENSITY (nv/ Hz) a. TMP5/TMP6 b. TMP7 k k FREQUENCY (Hz) Figure. Voltage Noise Spectral Density vs. Frequency b a 7- CHANGE (%) b a c V S = V, 5V a. TMP5 SOIC SOLDERED TO.5"." Cu PCB b. TMP6 SOIC SOLDERED TO.6"." Cu PCB c. TMP5 TO-9 IN SOCKET SOLDERED TO "." Cu PCB 5 6 TIME (s) Figure 9. Thermal Response Time in Stirred Oil Bath 7-5 Rev. F Page 7 of

8 FUNCTIONAL DESCRIPTION An equivalent circuit for the TMPx family of micropower, centigrade temperature sensors is shown in Figure. The core of the temperature sensor is a band gap core that comprises transistors Q and Q, biased by Q to approximately 8 μa. The band gap core operates both Q and Q at the same collector current level; however, because the emitter area of Q is times that of Q, the VBE of Q and the VBE of Q are not equal by the following relationship: A ΔV = BE VT ln A E,Q E,Q Resistors R and R are used to scale this result to produce the output voltage transfer characteristic of each temperature sensor and, simultaneously, R and R are used to scale the VBE of Q as an offset term in VOUT. Table 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 Q, which buffers the band gap core and provides load current drive. The current gain of Q, working with the available base current drive from the previous stage, sets the short-circuit current limit of these devices to 5 μa. V S SHUTDOWN Q Q X 6X Q Q X 7.5µA R 5µA Figure. Temperature Sensor Simplified Equivalent Circuit Table. TMPx Output Characteristics Sensor Offset Voltage (V) Output Voltage Scaling (mv/ C) TMP5 5 TMP TMP7 5 X R R X X 7-6 Output 5 C (mv) Rev. F Page 8 of

9 APPLICATIONS INFORMATION SHUTDOWN OPERATION All TMPx devices include a shutdown capability, which reduces the power supply drain to less than.5 μa maximum. This feature, available only in the SOIC_N and the SOT- 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 TMPx 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 on the SOT-). The shutdown response time of these temperature sensors is shown in Figure, Figure 5, and Figure 6. MOUNTING CONSIDERATIONS If the TMPx 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 C and 5 C. Properly cemented or glued to the surface of the medium, these sensors are within. C of the surface temperature. Caution should be exercised, especially with T- 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 TMPx 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. THERMAL ENVIRONMENT EFFECTS The thermal environment in which the TMPx sensors are used determines two important characteristics: self-heating effects and thermal response time. Figure illustrates a thermal model of the TMPx temperature sensors, which is useful in understanding these characteristics. PD C CH T J θ JC T C θ CA C C Figure. Thermal Circuit Model In the T- package, the thermal resistance junction-to-case, θjc, is C/W. The thermal resistance case-to-ambient, CA, is the difference between θja and θjc, 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 (θjc θca) TA Thus, the die temperature rise of a TMP5 SOT- package mounted into a socket in still air at 5 C and driven from a 5 V supply is less than. C. The transient response of the TMPx 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 7 and Figure 9 show the thermal response time of the TMPx sensors under various conditions. The thermal time constant of a temperature sensor is defined as the time required for the sensor to reach 6.% of the final value for a step change in the temperature. For example, the thermal time constant of a TMP5 SOIC package sensor mounted onto a.5"." PCB is less than 5 sec in air, whereas in a stirred oil bath, the time constant is less than sec. T A 7- Rev. F Page 9 of

10 BASIC TEMPERATURE SENSOR CONNECTIONS Figure illustrates the basic circuit configuration for the TMPx family of temperature sensors. The table in Figure shows the pin assignments of the temperature sensors for the three package types. For the SOT-, Pin is labeled NC, as are Pin, Pin, 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- or on the SOIC_N package, the SHUTDOWN pin should be connected to VS. SHUTDOWN PIN ASSIGNMENTS.7V < V S < 5.5V V S TMPx PACKAGE V S SHUTDOWN SOIC_N 8 5 SOT- 5 TO-9 NA Figure. Basic Temperature Sensor Circuit Configuration Note the. μf 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 (±. μf) placed across the. μf ceramic capacitor may offer additional noise immunity. 7- FAHRENHEIT THERMOMETERS Although the TMPx 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 5 shows an example of a simple Fahrenheit thermometer using either the TMP5 or the TMP7. Using the TMP5, this circuit can be used to sense temperatures from F to 57 F with an output transfer characteristic of mv/ F; using the TMP7, this circuit can be used to sense temperatures from F to F with an output transfer characteristic of mv/ F. This particular approach does not lend itself to the TMP6 because of its inherent.5 V output offset. The circuit is constructed with an AD589, a. V voltage reference, and four resistors whose values for each sensor are shown in the table in Figure 5. 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 R R = ( TMP5) ( AD589) R R R R where: TMP5 is the output voltage of the TMP5 or the TMP7 at the measurement temperature, TM. AD589 is the output voltage of the reference, that is,. 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. TMP5/ TMP7 AD589.V V S V S R R R R SENSOR TC R (kω) R (kω) R (kω) R (kω) TMP5 mv/ F 5. 7 TMP7 mv/ F 5. 8 Figure 5. TMP5/TMP7 Fahrenheit Thermometers 7- Rev. F Page of

11 The same circuit principles can be applied to the TMP6, but because of the inherent offset of the TMP6, the circuit uses only two resistors, as shown in Figure 6. In this circuit, the output voltage transfer characteristic is mv/ F but is referenced to the common ground of the circuit; however, there is a 58 mv (58 F) offset in the output voltage. For example, the output voltage of the circuit reads 8 mv if the TMP6 is placed in a F ambient environment and 5 mv at 57 F. V S V S TMP6 R 5.kΩ At the expense of additional circuitry, the offset produced by the circuit in Figure 6 can be avoided by using the circuit in Figure 7. In this circuit, the output of the TMP6 is conditioned by a single-supply, micropower op amp, the OP9. Although the entire circuit operates from a single V supply, the output voltage of the circuit reads the temperature directly, with a transfer characteristic of mv/ F, without offset. This is accomplished through an ADM66, which is a supply voltage inverter. The V supply is inverted and applied to the V terminal of the OP9. Thus, for a temperature range between F and 57 F, the output of the circuit reads mv to 57 mv. A general expression for the transfer equation of the circuit is given by R6 V OUT = R5 R6 R R ( ) R VS TMP6 mv/ F 58 F R F = 57 F = 5mV 7- Figure 6. TMP6 Fahrenheit Thermometer Version V R 5kΩ R R µf/ V S TMP6 R 5kΩ C µf R5 R6 7 OP9 mv/ F F T A 57 F 8 ELEMENT R R R5 R6 VALUE 58.6kΩ kω 7.7kΩ kω NC µf ADM V µf NC 7-5 Figure 7. TMP6 Fahrenheit Thermometer Version Rev. F Page of

12 AVERAGE AND DIFFERENTIAL TEMPERATURE MEASUREMENT 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 8 and Figure 9 demonstrate an inexpensive approach to average and differential temperature measurement. In Figure 8, an OP9 sums the outputs of three temperature sensors to produce an output voltage scaled by 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 9 illustrates how a pair of TMPx sensors used with an OP9 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 OP9 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 9. Using the TMP6, the output voltage of the circuit is scaled by 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 R to R. TMPx TMPx TMPx R kω R kω R kω R 7.5kΩ.7V < V S < 5.5V 7 OP9 6 V mv/ C FOR mv/ C FOR TMP7 R5 kω R6 7.5kΩ FOR R = R = R = R; V TEMP(AVG) = (TMPx TMPx TMPx ) R5 = R R = R6 Figure 8. Configuring Multiple Sensors for Average Temperature Measurements.7V < V S < 5.5V T T R8 5kΩ R R9 5kΩ R CENTERED AT R µf 7 OP9 R 6 R7 kω 7-6 C T A 5 C R5 kω R6 kω = T mv/ C V S CENTERED AT NOTE: R R, CADDOCK T9 k, OR EQUIVALENT. Figure 9. Configuring Multiple Sensors for Differential Temperature Measurements 7-7 Rev. F Page of

13 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 demonstrates one way to generate an interrupt using a TMP5, a CMP analog comparator, and a REF9, a V precision voltage reference. The circuit is designed to produce a logic high interrupt signal if the microprocessor temperature exceeds 8 C. This 8 C trip point was arbitrarily chosen (final value set by the microprocessor thermal reference design) and is set using an R to R voltage divider of the REF9 output voltage. Because the output of the TMP5 is scaled by mv/ C, the voltage at the inverting terminal of the CMP is set to.8 V..V 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 5 C 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 R and R determines the amount of comparator hysteresis. Using a. V supply, the output logic voltage swing of the CMP is.6 V; therefore, for a hysteresis of 5 C (5 mv/ C), R is set to kω, and R is set to MΩ. An expression for the hysteresis of this circuit is given by ( ) R V HYS = V LOGIC SWING, CMP R Because this circuit is probably used in close proximity to high speed digital circuits, R is split into equal values and a pf capacitor is used to form a low-pass filter on the output of the TMP5. Furthermore, to prevent high frequency noise from contaminating the comparator trip point, a. μf capacitor is used across R. R MΩ V S TMP5 R5 kω REF9 6 RA kω µf C L pf R 6kΩ RB kω R kω V REF 6 CMP 5 <8 C INTERRUPT >8 C C = CMP Figure. Microprocessor Overtemperature Interrupt Generator 7-8 Rev. F Page of

14 THERMOCOUPLE SIGNAL CONDITIONING WITH COLD-JUNCTION COMPENSATION The circuit in Figure conditions the output of a Type K thermocouple, while providing cold-junction compensation for temperatures between C and 5 C. The circuit operates from a single. V to 5.5 V supply and is designed to produce an output voltage transfer characteristic of mv/ C. A Type K thermocouple exhibits a Seebeck coefficient of approximately μv/ C; therefore, at the cold junction, the TMP5, with a temperature coefficient of mv/ C, is used with R and R to introduce an opposing cold-junction temperature coefficient of μv/ C. This prevents the isothermal, cold-junction connection between the PCB tracks of the circuit 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 C to 5 C. Over a 5 C measurement temperature range, the thermocouple produces an output voltage change of.5 mv. Because the required output full-scale voltage of the circuit is.5 V, the gain of the circuit is set to 6.. Choosing R equal to.99 kω sets R5 equal to. MΩ. Because the closest % value for R5 is. MΩ, a 5 kω potentiometer is used with R5 for fine trim of the full-scale output voltage. Although the OP9 is a superior single-supply, micropower operational amplifier, its output stage is not rail-to-rail; therefore, the C output voltage level is. V. If this circuit is digitized by a single-supply ADC, the ADC common should be adjusted to. V accordingly..v < V S < 5.5V V S TMP5 R MΩ 5% R.99kΩ R5.MΩ P 5kΩ TYPE K THERMO- COUPLE CHROMEL ALUMEL C T A 5 C COLD JUNCTION ISOTHERMAL BLOCK CU CU R.9kΩ R Ω 7 OP9 NOTE: ALL RESISTORS % UNLESS OTHERWISE NOTED. Figure. Single-Supply, Type K Thermocouple Signal Conditioning Circuit with Cold-Junction Compensation 6 V TO.5V R6 kω 5% 7-9 Rev. F Page of

15 USING TMPx SENSORS IN REMOTE LOCATIONS 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. Figure illustrates a way to convert the output voltage of a TMPx 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, the values of R and R were chosen to produce an arbitrary full-scale output current of 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..µf R.7kΩ V S TMPx N97 R 5V R TWISTED PAIR BELDEN TYPE 95 OR EQUIVALENT SENSOR R R TMP5 6 6 TMP TMP7 k k Figure. Remote, -Wire Boosted Output Current Temperature Sensor 7- TEMPERATURE TO ma LOOP TRANSMITTER In many process control applications, -wire transmitters are used to convey analog signals through noisy ambient environments. These current transmitters use a zero-scale signal current of ma, which can be used to power the signal conditioning circuitry of the transmitter. The full-scale output signal in these transmitters is ma. Figure illustrates a circuit that transmits temperature information in this fashion. Using a TMPx as the temperature sensor, the output current is linearly proportional to the temperature of the medium. The entire circuit operates from the V output of the REF9. The REF9 requires no external trimming because of its tight initial output voltage tolerance and the low supply current of the TMPx, the OP9, and the REF9. The entire circuit consumes less than ma from a total budget of ma. The OP9 regulates the output current to satisfy the current summation at the noninverting node of the OP9. A generalized expression for the KCL equation at Pin of the OP9 is given by I OUT = R7 TMPx R VREF R R R For each temperature sensor, Table 5 provides the values for the components P, P, and R to R. Table 5. Circuit Element Values for Loop Transmitter Sensor R P R P R R TMP kω 5 kω.58 MΩ kω kω 56. kω TMP kω 5 kω 9 kω 5 kω 97.6 kω 7 kω TMP kω 5 kω.5 kω 5 Ω 8.5 kω 8.5 kω The ma offset trim is provided by P, and P provides the full-scale gain trim of the circuit at ma. These two trims do not interact because the noninverting input of the OP9 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, D, is required in this circuit to prevent loop supply power-on transients from pulling the noninverting input of the OP9 more than 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 REF9; it is from 9 V to 8 V. Rev. F Page 5 of

16 V 6 REF9 R µf V LOOP 9V TO 8V V S P ma ADJUST TMPx R P ma ADJUST R D 7 OP9 R 6 R5 kω R6 kω Q N7 R L 5Ω NOTE: SEE TEXT FOR VALUES. D: HP58-8 R7 Ω Figure. Temperature to ma Loop Transmitter I L 7- TEMPERATURE-TO-FREQUENCY CONVERTER 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. The circuit in Figure illustrates a method by which the outputs of these temperature sensors can be converted to a frequency using the AD65. The output signal of the AD65 is a square wave that is proportional to the dc input voltage across Pin and Pin. The transfer equation of the circuit is given by f OUT V TPM V = ( RT CT ) OFFSET µf/ 5V V S TMPx P kω 5V R T R OFF 7Ω R P C T 5 8 f OUT OFFSET R OFF Ω 6 AD65 SENSOR R T (R P) C T TMP5.8kΩ 5Ω.7nF TMP6 TMP7 6.kΩ 5Ω 8.kΩ kω 7 R PU 5kΩ f OUT NB: ATT A (MIN), f OUT = Hz NOTE: R T AND C T SEE TABLE.8nF.nF Figure. Temperature-to-Frequency Converter 7- Rev. F Page 6 of

17 An offset trim network (fout OFFSET ) is included with this circuit to set fout to Hz when the minimum output voltage of the temperature sensor is reached. Potentiometer P is required to calibrate the absolute accuracy of the AD65. The table in Figure illustrates the circuit element values for each of the three sensors. The nominal offset voltage required for Hz output from the TMP5 is 5 mv; for the TMP6 and TMP7, the offset voltage required is mv. For the circuit values shown, the output frequency transfer characteristic of the circuit was set at 5 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 AD65. For complete information about the AD65 and the AD65, consult the individual data sheets for those devices. DRIVING LONG CABLES OR HEAVY CAPACITIVE LOADS Although the TMPx family of temperature sensors can drive capacitive loads up to, 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 5. 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. 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 (5 C) for 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 5 C and 5 C) over a shorter period of time (typically, between 5 and 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. V S TMPx 75Ω LONG CABLE OR HEAVY CAPACITIVE LOADS Figure 5. Driving Long Cables or Heavy Capacitive Loads 7- Rev. F Page 7 of

18 OUTLINE DIMENSIONS 5. (.968).8 (.89) (.57).8 (.97).5 (.98). (.) COPLANARITY. SEATING PLANE (.5) BSC 6. (.) 5.8 (.8).75 (.688).5 (.5).5 (.). (.).5 (.98).7 (.67).5 (.96).5 (.99).7 (.5). (.57) COMPLIANT TO JEDEC STANDARDS MS--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 A BSC.95 BSC.5 MAX.5 MIN.5 MAX.5 MIN.5 MAX.95 MIN SEATING PLANE. MAX.8 MIN 5.6 BSC Figure 6. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) COMPLIANT TO JEDEC STANDARDS MO-78-AA Figure 7. 5-Lead Small Outline Transistor Package [SOT-] (RJ-5) Dimensions shown in millimeters ---A. (5.).9 (.8).7 (.).5 (5.).9 (.8).75 (.5) FRONT VIEW. (.56).85 (.7).5 (.8).5 (.7) MIN SEATING PLANE.55 (.).5 (.7).5 (.5).5 (.68). (.5).95 (.).65 (.9).5 (.68).5 (.8).5 (.9).975 (.8).8 (.). (.5).7 (.). (.6) BOTTOM VIEW COMPLIANT TO JEDEC STANDARDS TO-6-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 8. -Pin Plastic Header-Style Package [TO-9] (T-) Dimensions shown in inches and (millimeters) 8- A Rev. F Page 8 of

19 ORDERING GUIDE Accuracy at Model, 5 C ( C max) Linear Operating Temperature Range Package Description TMP5/TMP6/TMP7 Package Option TMP5FSZ-REEL ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP5GRT-REEL7 ±. C to 5 C 5-Lead Small Outline Transistor Package (SOT-) RJ-5 T5G TMP5GRTZ-REEL7 ±. C to 5 C 5-Lead Small Outline Transistor Package (SOT-) RJ-5 #T TMP5GS ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP5GT9 ±. C to 5 C -Pin Plastic Header-Style Package (TO-9) T- TMP5GT9Z ±. C to 5 C -Pin Plastic Header-Style Package (TO-9) T- ADW75Z-REEL7 ±. C to 5 C 5-Lead Small Outline Transistor Package (SOT-) RJ-5 #T6G TMP6FS ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6FS-REEL ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6FSZ ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6FSZ-REEL ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6GRT-REEL7 ±. C to 5 C 5-Lead Small Outline Transistor Package (SOT-) RJ-5 T6G TMP6GRTZ-REEL7 ±. C to 5 C 5-Lead Small Outline Transistor Package (SOT-) RJ-5 #T6G TMP6GS ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6GS-REEL ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6GS-REEL7 ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6GSZ ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6GSZ-REEL ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6GSZ-REEL7 ±. C to 5 C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP6GT9 ±. C to 5 C -Pin Plastic Header-Style Package (TO-9) T- TMP6GT9Z ±. C to 5 C -Pin Plastic Header-Style Package (TO-9) T- TMP7FT9 ±. 5 C to C -Pin Plastic Header-Style Package (TO-9) T- TMP7FT9-REEL ±. 5 C to C -Pin Plastic Header-Style Package (TO-9) T- TMP7FT9Z ±. 5 C to C -Pin Plastic Header-Style Package (TO-9) T- TMP7GRT-REEL7 ±. 5 C to C 5-Lead Small Outline Transistor Package (SOT-) RJ-5 T7G TMP7GRTZ-REEL7 ±. 5 C to C 5-Lead Small Outline Transistor Package (SOT-) RJ-5 #T TMP7GSZ ±. 5 C to C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP7GSZ-REEL ±. 5 C to C 8-Lead Standard Small Outline Package (SOIC_N) R-8 TMP7GT9 ±. 5 C to C -Pin Plastic Header-Style Package (TO-9) T- TMP7GT9-REEL ±. 5 C to C -Pin Plastic Header-Style Package (TO-9) T- TMP7GT9Z ±. 5 C to C -Pin Plastic Header-Style Package (TO-9) T- Z = RoHS Compliant Part. W = Qualified for Automotive Applications. Branding Rev. F Page 9 of

20 AUTOMOTIVE PRODUCTS The ADW75Z-REEL7 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. 996 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D7--/(F) Rev. F Page of