Low Voltage Temperature Sensors TMP35/TMP36/TMP37

Transcription

1 FEATURES Low Voltge Opertion (.7 V to 5.5 V) Clirted Directly in C mv/ C Scle Fctor ( mv/ C on TMP7) C Accurcy over Temperture (Typ).5 C Linerity (Typ) Stle with Lrge Cpcitive Lods Specified C to +5 C, Opertion to +5 C Less thn 5 A Quiescent Current Shutdown Current.5 A Mx Low Self-Heting APPLICATIONS Environmentl Control Systems Therml Protection Industril Process Control Fire Alrms Power System Monitors CPU Therml Mngement Low Voltge Temperture Sensors TMP5/TMP6/TMP7 FUNCTIONAL BLOCK DIAGRAM SHUTDOWN +V s (.7V to 5.5V) TMP5/ TMP6/ TMP7 PACKAGE TYPES AVAILABLE RT-5 (SOT-) + NC TOP VIEW (Not to Scle) 5 NC = NO CONNECT SHUTDOWN PRODUCT DESCRIPTION The TMP5, TMP6, nd TMP7 re low voltge, precision centigrde temperture sensors. They provide voltge output tht is linerly proportionl to the Celsius (Centigrde) temperture. The TMP5/TMP6/TMP7 do not require ny externl clirtion to provide typicl ccurcies of ± C t +5 C nd ± C over the C to +5 C temperture rnge. The low output impednce of the TMP5/TMP6/TMP7 nd its liner output nd precise clirtion simplify interfcing to temperture control circuitry nd A/D converters. All three devices re intended for single-supply opertion from.7 V to 5.5 V mximum. Supply current runs well elow 5 µa, providing very low self-heting less thn. C in still ir. In ddition, shutdown function is provided to cut supply current to less thn.5 µa. The TMP5 is functionlly comptile with the LM5/LM5 nd provides 5 mv output t 5 C. The TMP5 reds tempertures from C to 5 C. The TMP6 is specified from C to +5 C, provides 75 mv output t 5 C, nd opertes to +5 C from single.7 V supply. The TMP6 is functionlly comptile with the LM5. Both the TMP5 nd TMP6 hve n output scle fctor of mv/ C. The TMP7 is intended for pplictions over the rnge 5 C to C nd provides n output scle fctor of mv/ C. The TMP7 provides 5 mv output t 5 C. Opertion extends to 5 C with reduced ccurcy for ll devices when operting from 5 V supply. The TMP5/TMP6/TMP7 re ll ville in low cost -led TO-9, SOIC-8, nd 5-led SOT- surfce-mount pckges. NC NC RN-8 (SOIC) TOP VIEW (Not to Scle) NC = NO CONNECT TO-9 BOTTOM VIEW (Not to Scle) NC 6 NC 5 SHUTDOWN PIN, +Vs; PIN, ; PIN, Informtion furnished y Anlog Devices is elieved to e ccurte nd relile. However, no responsiility is ssumed y Anlog Devices for its use, nor for ny infringements of ptents or other rights of third prties tht my result from its use. No license is grnted y impliction or otherwise under ny ptent or ptent rights of Anlog Devices. One Technology Wy, P.O. Box 96, Norwood, MA 6-96, U.S.A. Tel: 78/9-7 Fx: 78/6-87 Anlog Devices, Inc.,

2 TMP5/TMP6/TMP7 SPECIFICATIONS ( =.7 V to 5.5 V, C T A +5 C, unless otherwise noted.) Prmeter Symol Conditions Min Typ Mx Unit ACCURACY TMP5/TMP6/TMP7F T A = 5 C ± ± C TMP5/TMP6/TMP7G T A = 5 C ± ± C TMP5/TMP6/TMP7F Over Rted Temperture ± ± C TMP5/TMP6/TMP7G Over Rted Temperture ± ± C Scle Fctor, TMP5 C T A 5 C 9.8/. mv/ C Scle Fctor, TMP6 C T A +5 C 9.8/. mv/ C Scle Fctor, TMP7 5 C T A 85 C 9.6/. mv/ C 5 C T A C 9.6/. mv/ C. V V Lod Regultion µa I L 5 µa C T A +5 C 6 m C/µA 5 C T A +5 C 5 6 m C/µA Power Supply Rejection Rtio PSRR T A = 5 C m C/V. V V 5 m C/V Linerity.5 C Long-Term Stility T A = 5 C for khrs. C SHUTDOWN Logic High Input Voltge V IH =.7 V.8 V Logic Low Input Voltge V IL = 5.5 V mv OUTPUT TMP5 Output Voltge T A = 5 C 5 mv TMP6 Output Voltge T A = 5 C 75 mv TMP7 Output Voltge T A = 5 C 5 mv Output Voltge Rnge mv Output Lod Current I L 5 µa Short-Circuit Current I SC Note 5 µa Cpcitive Lod Driving C L No Oscilltions pf Device Turn-On Time Output within ± C.5 ms kω pf Lod POWER SUPPLY Supply Rnge V Supply Current I SY (ON) Unloded 5 µa Supply Current (Shutdown) I SY (OFF) Unloded..5 µa NOTES Does not consider errors cused y self-heting. Gurnteed ut not tested. Specifictions suject to chnge without notice. 5 LOAD REG m C/ A Figure. Lod Reg vs. Temperture (m C/µA)

3 TMP5/TMP6/TMP7,, ABSOLUTE MAXIMUM RATINGS Supply Voltge V Shutdown Pin SHUTDOWN + Output Pin Operting Temperture Rnge C to +5 C Dice Junction Temperture C Storge Temperture Rnge C to +6 C Led Temperture (Soldering, 6 sec) C NOTES Stresses ove those listed under Asolute Mximum Rtings my cuse permnent dmge to the device. This is stress rting only; functionl opertion t or ove this specifiction is not implied. Exposure to mximum rting conditions for extended periods my ffect device reliility. Digitl inputs re protected; however, permnent dmge my occur on unprotected units from high energy electrosttic fields. Keep units in conductive fom or pckging t ll times until redy to use. Use proper ntisttic hndling procedures. Remove power efore inserting or removing units from their sockets. Pckge Type JA JC Unit TO-9 (T9 Suffix) 6 C/W SOIC-8 (S Suffix) 58 C/W SOT- (RT Suffix) 8 C/W θ JA is specified for device in socket (worst-cse conditions). ORDERING GUIDE Accurcy Liner t 5 C Operting Pckge Model ( C mx) Temperture Rnge Options TMP5FT9 ±. C to 5 C TO-9 TMP5GT9 ±. C to 5 C TO-9 TMP5FS ±. C to 5 C RN-8 TMP5GS ±. C to 5 C RN-8 TMP5GRT ±. C to 5 C RT-5 TMP6FT9 ±. C to +5 C TO-9 TMP6GT9 ±. C to +5 C TO-9 TMP6FS ±. C to +5 C RN-8 TMP6GS ±. C to +5 C RN-8 TMP6GRT ±. C to +5 C RT-5 TMP7FT9 ±. 5 C to C TO-9 TMP7GT9 ±. 5 C to C TO-9 TMP7FS ±. 5 C to C RN-8 TMP7GS ±. 5 C to C RN-8 TMP7GRT ±. 5 C to C RT-5 NOTES SOIC = Smll Outline Integrted Circuit; RT = Plstic Surfce Mount; TO = Plstic. Consult fctory for vilility. FUNCTIONAL DESCRIPTION An equivlent circuit for the TMPx fmily of micropower, centigrde temperture sensors is shown in Figure. At the hert of the temperture sensor is nd gp core, which is comprised of trnsistors Q nd Q, ised y Q to pproximtely 8 µa. The nd gp core opertes oth Q nd Q t the sme collector current level; however, since the emitter re of Q is times tht of Q, Q s V BE nd Q s V BE re not equl y the following reltionship: + SHDN + Q V BE =V T ln Q X 6X Q Q X 7.5 A A E,Q A E,Q R 5 A Figure. Temperture Sensor Simplified Equivlent Circuit Resistors R nd R re used to scle this result to produce the output voltge trnsfer chrcteristic of ech temperture sensor nd, simultneously, R nd R re used to scle Q s V BE s n offset term in. Tle I summrizes the differences etween the three temperture sensors output chrcteristics. Tle I. TMPx Output Chrcteristics Offset Output Voltge Output Voltge Sensor Voltge (V) Scling (mv/ 5 C (mv) TMP5 5 TMP TMP7 5 X R R X X The output voltge of the temperture sensor is ville t the emitter of Q, which uffers the nd gp core nd provides lod current drive. Q s current gin, working with the ville se current drive from the previous stge, sets the short-circuit current limit of these devices to 5 µa. CAUTION ESD (electrosttic dischrge) sensitive device. Electrosttic chrges s high s V redily ccumulte on the humn ody nd test equipment nd cn dischrge without detection. Although the TMP5/TMP6/TMP7 fetures proprietry ESD protection circuitry, permnent dmge my occur on devices sujected to high energy electrosttic dischrges. Therefore, proper ESD precutions re recommended to void performnce degrdtion or loss of functionlity. WARNING! ESD SENSITIVE DEVICE

4 TMP5/TMP6/TMP7 Typicl Performnce Chrcteristics OUTPUT VOLTAGE V TMP5. TMP6 c. TMP7 = V c POWER SUPPLY REJECTION C/V TPC. Output Voltge vs. Temperture. k k k FREQUENCY Hz TPC. Power Supply Rejection vs. Frequency ACCURACY ERROR C 5. MAXIMUM LIMIT (G GRADE). TYPICAL ACCURACY ERROR c. MINIMUM LIMIT (G GRADE) c TPC. Accurcy Error vs. Temperture MINIMUM SUPPLY VOLTAGE V 5 MINIMUM SUPPLY VOLTAGE REQUIRED TO MEET DATA SHEET SPECIFICATION NO LOAD. TMP5/TMP6. TMP TPC 5. Minimum Supply Voltge vs. Temperture. 6 POWER SUPPLY REJECTION C/V... V+ = V to 5.5V, NO LOAD SUPPLY CURRENT A 5. V+ = 5V. V+ = V NO LOAD TPC. Power Supply Rejection vs. Temperture TPC 6. Supply Current vs. Temperture

5 TMP5/TMP6/TMP7 5 T A = 5 C, NO LOAD = SHUTDOWN PIN HIGH TO LOW (V TO V) SUPPLY CURRENT A RESPONSE TIME s = SHUTDOWN PIN LOW TO HIGH (V TO V) SETTLES WITHIN ± C SUPPLY VOLTAGE V TPC 7. Supply Current vs. Supply Voltge TPC. Response Time for Shutdown Pin vs. Temperture SUPPLY CURRENT na 5. V+ = 5V. V+ = V NO LOAD TPC 8. Supply Current vs. Temperture (Shutdown = V) OUTPUT VOLTAGE V T A = 5 C V+ = V SHUTDOWN = SIGNAL T A = 5 C V+ AND SHUTDOWN = SIGNAL TIME µs TPC. Response Time to Shutdown nd V+ Pins vs. Time RESPONSE TIME s = V+ AND SHUTDOWN PINS HIGH TO LOW (V TO V) = V+ AND SHUTDOWN PINS LOW TO HIGH (V TO V) SETTLES WITHIN ± C PERCENT OF CHANGE % c V IN = V, 5V. TMP5 SOIC SOLDERED TO.5" x." Cu PCB. TMP6 SOIC SOLDERED TO.6" x." Cu PCB c. TMP5 TO-9 IN SOCKET SOLDERED TO " x." Cu PCB TPC 9. Response Time for V+ Power-Up/Power- Down vs. Temperture 5 6 TIME sec TPC. Therml Response Time in Still Air 5

6 TMP5/TMP6/TMP7 TIME CONSTANT sec 8 6. TMP5 SOIC SOLDERED TO.5" x." Cu PCB. TMP6 SOIC SOLDERED TO.6" x." Cu PC c. TMP5 TO-9 IN SOCKET SOLDERED TO " x." Cu PCB V IN = V, 5V c VOLT/DIVISION 9 % mv ms AIR VELOCITY FPM TPC. Therml Response Time Constnt in Forced Air TIME/DIVISION TPC 5. Temperture Sensor Widend Output Noise Voltge. Gin =, BW = 57 khz CHANGE % c V IN = V, 5V. TMP5 SOIC SOLDERED TO.5" x." Cu PCB. TMP6 SOIC SOLDERED TO.6" x." Cu PCB c. TMP5 TO-9 IN SOCKET SOLDERED TO " x." Cu PCB VOLTAGE NOISE DENSITY nv/ Hz TMP5/6. TMP7 5 6 TIME sec TPC. Therml Response Time in Stirred Oil Bth k k FREQUENCY Hz TPC 6. Voltge Noise Spectrl Density vs. Frequency 6

7 TMP5/TMP6/TMP7 APPLICATIONS SECTION Shutdown Opertion All TMPx devices include shutdown cpility tht reduces the power supply drin to less thn.5 µa mximum. This feture, ville only in the SOIC-8 nd the SOT- pckges, is TTL/ CMOS level comptile, provided tht the temperture sensor supply voltge is equl in mgnitude to the logic supply voltge. Internl to the TMPx t the SHUTDOWN pin, pull-up current source to V IN is connected. This permits the SHUTDOWN pin to e driven from n open-collector/drin driver. A logic LOW, or zero-volt condition on the SHUTDOWN pin, is required to turn the output stge OFF. During shutdown, the output of the temperture sensors ecomes high impednce stte where the potentil of the output pin would then e determined y externl circuitry. If the shutdown feture is not used, it is recommended tht the SHUTDOWN pin e connected to V IN (Pin 8 on the SOIC-8, Pin on the SOT-). The shutdown response time of these temperture sensors is illustrted in TPCs 9,, nd. Mounting Considertions If the TMPx temperture sensors re thermlly ttched nd protected, they cn e used in ny temperture mesurement ppliction where the mximum temperture rnge of the medium is etween C to +5 C. Properly cemented or glued to the surfce of the medium, these sensors will e within. C of the surfce temperture. Cution should e exercised, especilly with TO-9 pckges, ecuse the leds nd ny wiring to the device cn ct s het pipes, introducing errors if the surrounding ir-surfce interfce is not isotherml. Avoiding this condition is esily chieved y ding the leds of the temperture sensor nd the hookup wires with ed of thermlly conductive epoxy. This will ensure tht the TMPx die temperture is not ffected y the surrounding ir temperture. Becuse plstic IC pckging technology is used, excessive mechnicl stress should e voided when fstening the device with clmp or screw-on het t. Thermlly conductive epoxy or glue, which must e electriclly nonconductive, is recommended under typicl mounting conditions. These temperture sensors, s well s ny ssocited circuitry, should e kept insulted nd dry to void lekge nd corrosion. In wet or corrosive environments, ny electriclly isolted metl or cermic well cn e used to shield the temperture sensors. Condenstion t very cold tempertures cn cuse errors nd should e voided y seling the device, using electriclly nonconductive epoxy pints or dip or ny one of mny printed circuit ord cotings nd vrnishes. Therml Environment Effects The therml environment in which the TMPx sensors re used determines two importnt chrcteristics: self-heting effects nd therml response time. Illustrted in Figure is therml model of the TMPx temperture sensors tht is useful in understnding these chrcteristics. T J JC T C CA In the TO-9 pckge, the therml resistnce junction-to-cse, θ JC, is C/W. The therml resistnce cse-to-mient, θ CA, is the difference etween θ JA nd θ JC, nd is determined y the chrcteristics of the therml connection. The temperture sensor s power dissiption, represented y P D, is the product of the totl voltge cross the device nd its totl supply current (including ny current delivered to the lod). The rise in die temperture ove the medium s mient temperture is given y: TJ = PD ( θjc + θca)+ TA Thus, the die temperture rise of TMP5 RT pckge mounted into socket in still ir t 5 C nd driven from 5 V supply is less thn. C. The trnsient response of the TMPx sensors to step chnge in the temperture is determined y the therml resistnces nd the therml cpcities of the die, C CH, nd the cse, C C. The therml cpcity of the cse, C C, vries with the mesurement medium since it includes nything in direct contct with the pckge. In ll prcticl cses, the therml cpcity of the cse is the limiting fctor in the therml response time of the sensor nd cn e represented y single-pole RC time constnt response. TPCs nd illustrte the therml response time of the TMPx sensors under vrious conditions. The therml time constnt of temperture sensor is defined s the time required for the sensor to rech 6.% of the finl vlue for step chnge in the temperture. For exmple, the therml time constnt of TMP5 S pckge sensor mounted onto.5" y." PCB is less thn 5 sec in ir, wheres in stirred oil th, the time constnt is less thn seconds. Bsic Temperture Sensor Connections Figure illustrtes the sic circuit configurtion for the TMPx fmily of temperture sensors. The tle shown in the figure illustrtes the pin ssignments of the temperture sensors for the three pckge types. For the SOT-, Pin is leled s NC s re Pins,, 6, nd 7 on the SOIC-8 pckge. It is recommended tht no electricl connections e mde to these pins. If the shutdown feture is not needed on the SOT- or the SOIC-8 pckge, the SHUTDOWN pin should e connected to. SHDN PIN ASSIGNMENTS.7V < Vs < 5.5V Vs TMPx PACKAGE SHDN SOIC SOT--5 5 TO-9 NA Figure. Bsic Temperture Sensor Circuit Configurtion P D C CH C C T A Figure. Therml Circuit Model 7

8 TMP5/TMP6/TMP7 Note the. µf ypss cpcitor on the input. This cpcitor should e cermic type, hve very short leds (surfce mount would e preferle), nd e locted s close physicl proximity to the temperture sensor supply pin s prcticl. Since these temperture sensors operte on very little supply current nd could e exposed to very hostile electricl environments, it is importnt to minimize the effects of RFI (rdio frequency interference) on these devices. The effect of RFI on these temperture sensors in specific nd nlog ICs in generl is mnifested s norml dc shifts in the output voltge due to the rectifiction of the high frequency mient noise y the IC. In those cses where the devices re operted in the presence of high frequency rdited or conducted noise, lrge vlue tntlum cpcitor (. µf) plced cross the. µf cermic my offer dditionl noise immunity. Fhrenheit Thermometers Although the TMPx temperture sensors re centigrde temperture sensors, few components cn e used to convert the output voltge nd trnsfer chrcteristics to directly red Fhrenheit tempertures. Shown in Figure 5 is n exmple of simple Fhrenheit thermometer using either the TMP5 or the TMP7. This circuit cn e used to sense tempertures from F to 57 F, with n output trnsfer chrcteristic of mv/ F using the TMP5 nd from F to F using the TMP7 with n output chrcteristic of mv/ F. This prticulr pproch does not lend itself well to the TMP6 ecuse of its inherent.5 V output offset. The circuit is constructed with n AD589,. V voltge reference, nd four resistors whose vlues for ech sensor re shown in the figure tle. The scling of the output resistnce levels ws to ensure minimum output loding on the temperture sensors. A generlized expression for the circuit s trnsfer eqution is given y: R R = R+ R ( TMP 5)+ R+ R AD589 ( ) where: TMP5 = Output voltge of the TMP5, or the TMP7, t the mesurement temperture, T M, nd AD589 = Output voltge of the reference =. V. Note tht the output voltge of this circuit is not referenced to the circuit s common. If this output voltge were to e pplied directly to the input of n ADC, the ADC s common should e djusted ccordingly. TMP5/7 AD589.V PIN ASSIGNMENTS SENSOR TC R (k ) R (k ) R (k ) R (k ) TMP5 mv/ F 5. 7 TMP7 mv/ F 5. 8 R R R R The sme circuit principles cn e pplied to the TMP6, ut ecuse of the TMP6 s inherent offset, the circuit uses two less resistors s shown in Figure 5. In this circuit, the output voltge trnsfer chrcteristic is mv/ F ut is referenced to the circuit s common; however, there is 58 mv (58 F) offset in the output voltge. For exmple, the output voltge of the circuit would red 8 mv were the TMP6 plced in F mient environment nd 5 mv t 57 F. TMP6 R 5.k R F = +57 F = mv/ F 58 F Figure 5. TMP6 Fhrenheit Thermometer Version At the expense of dditionl circuitry, the offset produced y the circuit in Figure 5 cn e voided y using the circuit in Figure 5c. In this circuit, the output of the TMP6 is conditioned y singlesupply, micropower op mp, the OP9. Although the entire circuit opertes from single V supply, the output voltge of the circuit reds the temperture directly, with trnsfer chrcteristic of mv/ F, without offset. This is ccomplished through the use of n ADM66, supply voltge inverter. The V supply is inverted nd pplied to the P9 s V terminl. Thus, for temperture rnge etween F nd +57 F, the output of the circuit reds mv to +57 mv. A generl expression for the circuit s trnsfer eqution is given y: R6 R = R5+ R6 + R ( TMP 6) R R Averge nd Differentil Temperture Mesurement In mny commercil nd industril environments, temperture sensors re often used to mesure the verge temperture in uilding, or the difference in temperture etween two loctions on fctory floor or in n industril process. The circuits in Figures 6 nd 6 demonstrte n inexpensive pproch to verge nd differentil temperture mesurement. In Figure 6, n OP9 is used to sum the outputs of three temperture sensors to produce n output voltge scled y mv/ C tht represents the verge temperture t three loctions. The circuit cn e extended to s mny temperture sensors s required s long s the circuit s trnsfer eqution is mintined. In this ppliction, it is recommended tht one temperture sensor type e used throughout the circuit; otherwise, the output voltge of the circuit will not produce n ccurte reding of the vrious mient conditions. Figure 5. TMP5/TMP7 Fhrenheit Thermometers 8

9 TMP5/TMP6/TMP7 +V R 5k R R F/ TMP6 R 5k C F R5 R6 8 OP9 mv/ F F T A +57 F 8 ELEMENT R R R5 R6 TMP6 58.6k k 7.7k k NC F ADM V F NC Figure 5c. TMP6 Fhrenheit Thermometer Version The circuit in Figure 6 illustrtes how pir of TMPx sensors cn e used with n OP9 configured s difference mplifier to red the difference in temperture etween two loctions. In these pplictions, it is lwys possile tht one temperture sensor would e reding temperture elow tht of the other sensor. To ccommodte this condition, the output of the OP9 is offset to voltge t one-hlf the supply vi R5 nd R6. Thus, the output voltge of the circuit is mesured reltive to this point, s shown in the figure. Using the TMP6, the output voltge of the circuit is scled y mv/ C. To minimize error in the difference etween the two mesured tempertures, common, redily ville thin-film resistor network is used for R R..7V < < 5.5V.7V < + < 5.5V 7 OP9 V mv/ C FOR mv/ C FOR TMP5/6 T R* R8 5k R* TMPx TMPx TMPx R k R k R k R 7.5k R5 k R6 7.5k FOR R = R = R = R; V TEMP(AVG) = (TMPx + TMPx + TMPx ) R5 = R R = R6 T T A 5 C R* R* R9 5k CENTERED AT R5 k F R6 k 7 OP9 6 R7 k = T mv/ C V CENTERED AT S *R R, CADDOCK T9 k, OR EQUIVALENT Figure 6. Configuring Multiple Sensors for Averge Temperture Mesurements Figure 6. Configuring Multiple Sensors for Differentil Temperture Mesurements 9

10 TMP5/TMP6/TMP7 Microprocessor Interrupt Genertor These inexpensive temperture sensors cn e used with voltge reference nd n nlog comprtor to configure n interrupt genertor useful in microprocessor pplictions. With the populrity of fst 86 nd Pentium lptop computers, the need to indicte microprocessor overtemperture condition hs grown tremendously. The circuit illustrted in Figure 7 demonstrtes one wy to generte n interrupt using TMP5, CMP nlog comprtor, nd REF9, V precision voltge reference. The circuit hs een designed to produce logic HIGH interrupt signl if the microprocessor temperture exceeds 8 C. This 8 C trip point ws ritrrily chosen (finl vlue set y the microprocessor therml reference design) nd is set using n R R voltge divider of the REF9 s output voltge. Since the output of the TMP5 is scled y mv/ C, the voltge t the CMP s inverting terminl is set to.8 V. Since temperture is slowly moving quntity, the possiility for comprtor chtter exists. To void this condition, hysteresis is used round the comprtor. In this ppliction, hysteresis of 5 C out the trip point ws ritrrily chosen; the ultimte vlue for hysteresis should e determined y the end ppliction. The output logic voltge swing of the comprtor with R nd R determine the mount of comprtor hysteresis. Using. V supply, the output logic voltge swing of the CMP is.6 V; thus, for hysteresis of 5 C (5 mv/ C), R is set to kω nd R is set to MΩ. An expression for this circuit s hysteresis is given y: V HYS = R R V LOGIC SWING, CMP ( ) Becuse of the likelihood tht this circuit would e used in close proximity to high speed digitl circuits, R is split into equl vlues nd pf is used to form low-pss filter on the output of the TMP5. Furthermore, to prevent high frequency noise from contminting the comprtor trip point,. µf cpcitor is used cross R. Thermocouple Signl Conditioning with Cold-Junction Compenstion The circuit in Figure 8 conditions the output of Type K thermocouple, while providing cold-junction compenstion for tempertures etween C nd 5 C. The circuit opertes from single. V to 5.5 V supplies nd hs een designed to produce n output voltge trnsfer chrcteristic of mv/ C. A Type K thermocouple exhiits Seeeck coefficient of pproximtely µv/ C; therefore, t the cold junction, the TMP5, with temperture coefficient of mv/ C, is used with R nd R to introduce n opposing cold-junction temperture coefficient of µv/ C. This prevents the isotherml, cold-junction connection etween the circuit s PCB trcks nd the thermocouple s wires from introducing n error in the mesured temperture. This compenstion works extremely well for circuit mient tempertures in the rnge of C to 5 C. Over 5 C mesurement temperture rnge, the thermocouple produces n output voltge chnge of.5 mv. Since the required circuit s output full-scle voltge is.5 V, the gin of the circuit is set to 6.. Choosing R equl to.99 kω sets R5 equl to. MΩ. Since the closest % vlue for R5 is. MΩ, 5 kω potentiometer is used with R5 for fine trim of the full-scle output voltge. Although the OP9 is superior single-supply, micropower opertionl mplifier, its output stge is not ril-to-ril; s such, the C output voltge level is. V. If this circuit were to e digitized y single-supply ADC, the ADC s common should e djusted to. V ccordingly. Using TMPx Sensors in Remote Loctions In mny industril environments, sensors re required to operte in the presence of high mient noise. These noise sources tke on mny forms; for exmple, SCR trnsients, relys, rdio trnsmitters, rc welders, c motors, nd so on. They my lso e used t considerle distnces from the signl conditioning circuitry. These high noise environments re very typiclly in the form of electric fields, so the voltge output of the temperture sensor cn e susceptile to contmintion from these noise sources..v R M TMP5 R5 k REF9 6 RA k F C L pf R 6k RB k R k 6 5 V REF C <8 C INTERRUPT >8 C C = CMP Pentium is registered trdemrk of Intel Corportion. Figure 7. Pentium Overtemperture Interrupt Genertor

11 TMP5/TMP6/TMP7.V < < 5.5V TMP5 R M 5% R.99k R5*.M P 5k TYPE K THERMO- COUPLE CHROMEL ALUMEL C T 5 C COLD JUNCTION ISOTHERMAL BLOCK CU CU R*.9k R* NOTE: ALL RESISTORS % UNLESS OTHERWISE NOTED 7 OP9 6 V.5V R6 k 5% Figure 8. A Single-Supply, Type K Thermocouple Signl Conditioning Circuit with Cold-Junction Compenstion Illustrted in Figure 9 is wy to convert the output voltge of TMPx sensor into current to e trnsmitted down long twisted-pir shielded cle to ground referenced receiver. The temperture sensors do not possess the cpility of high output current opertion; thus, grden vriety PNP trnsistor is used to oost the output current drive of the circuit. As shown in the tle, the vlues of R nd R were chosen to produce n ritrry full-scle output current of ma. Lower vlues for the full-scle current re not recommended. The minimum-scle output current produced y the circuit could e contminted y nery mient mgnetic fields operting in the vicinity of the circuit/cle pir. Becuse of the use of n externl trnsistor, the minimum recommended operting voltge for this circuit is 5 V. Note, to minimize the effects of EMI (or RFI), oth the circuit s nd the temperture sensor s supply pins re ypssed with good qulity, cermic cpcitors.. F R.7k TMPx N97 5V R A Temperture to ma Loop Trnsmitter In mny process control pplictions, -wire trnsmitters re used to convey nlog signls through noisy mient environments. These current trnsmitters use zero-scle signl current of ma tht cn e used to power the trnsmitter s signl conditioning circuitry. The full-scle output signl in these trnsmitters is ma. A circuit tht trnsmits temperture informtion in this fshion is illustrted in Figure. Using TMPx s the temperture sensor, the output current is linerly proportionl to the temperture of the medium. The entire circuit opertes from the V output of the REF9. The REF9 requires no externl trimming for two resons: () the REF9 s tight initil output voltge tolernce nd () the low supply current of TMPx, the OP9 nd the REF9. The entire circuit consumes less thn ma from totl udget of ma. The OP9 regultes the output current to stisfy the current summtion t the noninverting node of the OP9. A generlized expression for the KCL eqution t the OP9 s Pin is given y: I OUT = R 7 TMP x R + V REF R R R For ech of the three temperture sensors, the tle elow illustrtes the vlues for ech of the components, P, P, nd R R: R Tle II. Circuit Element Vlues for Loop Trnsmitter SENSOR R R TMP5 6 6 TMP TMP7 k k TWISTED PAIR BELDEN TYPE 95 OR EQUIVALENT Sensor R( ) P( ) R( ) P( ) R( ) R( ) TMP k 5 k.58 M k k 56. k TMP k 5 k 9 k 5 k 97.6 k 7 k TMP k 5 k.5 k k 8.5 k Figure 9. A Remote, -Wire Boosted Output Current Temperture Sensor

12 TMP5/TMP6/TMP7 The ma offset trim is provided y P, nd P provides the circuit s full-scle gin trim t ma. These two trims do not interct ecuse the noninverting input of the OP9 is held t virtul ground. The zero-scle nd full-scle output currents of the circuit re djusted ccording to the operting temperture rnge of ech temperture sensor. The Schottky diode, D, is required in this circuit to prevent loop supply power-on trnsients from pulling the noninverting input of the OP9 more thn mv elow its inverting input. Without this diode, such trnsients could cuse phse reversl of the opertionl mplifier nd possile ltchup of the trnsmitter. The loop supply voltge complince of the circuit is limited y the mximum pplied input voltge to the REF9 nd is from 9 V to 8 V. A Temperture to Frequency Converter Another common method of trnsmitting nlog informtion from remote loction is to convert voltge to n equivlent in the frequency domin. This is redily done with ny of the low cost, monolithic voltge-to-frequency converters (VFCs) ville. These VFCs feture roust, open-collector output trnsistor for esy interfcing to digitl circuitry. The digitl signl produced y the VFC is less susceptile to contmintion from externl noise sources nd line voltge drops ecuse the only importnt informtion is the frequency of the digitl signl. As long s the conversions etween temperture nd frequency re done ccurtely, the temperture dt from the sensors cn e relily trnsmitted. The circuit in Figure illustrtes method y which the outputs of these temperture sensors cn e converted to frequency using the AD65. The output signl of the AD65 is squre wve tht is proportionl to the dc input voltge cross Pins nd. The trnsfer eqution of the circuit is given y: f OUT = V TMP V OFFSET R T C T ( ) F/ TMPx P k 5V 5V R T * R OFF 7 R P C T * 5 8 f OUT OFFSET R OFF 6 AD65 SENSOR R T (R + P) C T TMP5 TMP6 TMP7.8k k k + k 7 R PU 5k f OUT NB: ATT A (min), f OUT = Hz *R T AND C T SEE TABLE.7nF.8nF.nF Figure. A Temperture-to-Frequency Converter An offset trim network (f OUT OFFSET ) is included with this circuit to set f OUT t Hz when the temperture sensor s minimum output voltge is reched. Potentiometer P is required to clirte the solute ccurcy of the AD65. The tle in Figure illustrtes the circuit element vlues for ech of the three sensors. The nominl offset voltge required for Hz output from the TMP5 is 5 mv; for the TMP6 nd TMP7, the offset voltge required is mv. In ll cses for the circuit vlues shown, the output frequency trnsfer chrcteristic of the circuit ws set t 5 Hz/ C. At the receiving end, frequency-to-voltge converter (FVC) cn e used to convert the frequency ck to dc voltge for further processing. One such FVC is the AD65. For complete informtion on the AD65 nd AD65, plese consult the individul dt sheets for those devices. V 6 REF9 R* F V LOOP 9V TO 8V P* ma ADJUST TMPx R* P* ma ADJUST R* D R* 7 R5 k R6 k Q N7 R L 5 *SEE TEXT FOR VALUES D: HP58 8 R7 A: OP9 I L Figure. A Temperture to -to- ma Loop Trnsmitter

13 TMP5/TMP6/TMP7 Driving Long Cles or Hevy Cpcitive Lods Although the TMPx fmily of temperture sensors is cple of driving cpcitive lods up to, pf without oscilltion, output voltge trnsient response times cn e improved with the use of smll resistor in series with the output of the temperture sensor, s shown in Figure. As n dded enefit, this resistor forms low-pss filter with the cle s cpcitnce, which helps to reduce ndwidth noise. Since the temperture sensor is likely to e used in environments where the mient noise level cn e very high, this resistor helps to prevent rectifiction y the devices of the high frequency noise. The comintion of this resistor nd the supply ypss cpcitor offers the est protection. + Commentry on Long-Term Stility The concept of long-term stility hs een used for mny yers to descrie y wht mount n IC s prmeter would shift during its lifetime. This is concept tht hs een typiclly pplied to oth voltge references nd monolithic temperture sensors. Unfortuntely, integrted circuits cnnot e evluted t room temperture (5 C) for yers or so to determine this shift. As result, mnufcturers very typiclly perform ccelerted lifetime testing of integrted circuits y operting ICs t elevted tempertures (etween 5 C nd 5 C) over shorter period of time (typiclly, etween 5 nd hours). As result of this opertion, the lifetime of n integrted circuit is significntly ccelerted due to the increse in rtes of rection within the semiconductor mteril. TMPx 75 LONG CABLE OR HEAVY CAPACITIVE LOADS Figure. Driving Long Cles or Hevy Cpcitive Lods

14 TMP5/TMP6/TMP7 OUTLINE DIMENSIONS -Pin Plstic Heder-Style Pckge [TO-9] (TO-9) Dimensions shown in inches nd (millimeters) 8-Led Stndrd Smll Outline Pckge [SOIC] Nrrow Body (RN-8) Dimensions shown in millimeters nd (inches) SEATING PLANE.5 (.) MIN.5 (.7) MIN.5 (.66).95 (.).5 (.9).8 (.).5 (5.).75 (.5). (5.).7 (.).5 (.7) MAX.9 (.8) SQ.6 (.7).55 (.).5 (.5). (.57).8 (.97).5 (.98). (.) COPLANARITY. 5. (.968).8 (.89) 8 5 SEATING PLANE.7 (.5) BSC 6. (.) 5.8 (.8).75 (.688).5 (.5).5 (.). (.).5 (.98).9 (.75) 8.5 (.96).5 (.99) 5.7 (.5). (.6) 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.5 (.9).8 (.) BOTTOM VIEW.65 (.9).5 (.8) COMPLIANT TO JEDEC STANDARDS TO-6AA CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETERS DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN 5-Led Plstic Surfce-Mount Pckge [SOT-] (RT-5) Dimensions shown in millimeters.9 BSC 5.6 BSC.8 BSC..5.9 PIN.9 BSC.95 BSC.5 MAX.5 MAX.5. SEATING PLANE..8 COMPLIANT TO JEDEC STANDARDS MO-78AA.6.5. Revision History Loction Pge / Dt Sheet chnged from REV. B to. Deleted text from Commentry on Long-Term Stility section Updte OUTLINE DIMENSIONS

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16 C7 /(C) PRINTED IN U.S.A. 6