connection diagram pin 3 pin 2 pin 1 (? (nc) (+) pin 2 can be either attached or unconnected bottom view * rev. a 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 which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of analog devices. a ad592* one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 617/329-4700 fax: 617/326-8703 low cost, precision ic temperature transducer features high precalibrated accuracy: 0.5 8 c max @ +25 8 c excellent linearity: 0.15 8 c max (0 8 c to +70 8 c) wide operating temperature range: C25 8 c to +105 8 c single supply operation: +4 v to +30 v excellent repeatability and stability high level output: 1 m a/k two terminal monolithic ic: temperature in/ current out minimal self-heating errors product description the ad592 is a two terminal monolithic integrated circuit tem- perature transducer that provides an output current propor- tional to absolute temperature. for a wide range of supply voltages the transducer acts as a high impedance temperature dependent current source of 1 m a/k. improved design and laser wafer trimming of the ics thin film resistors allows the ad592 to achieve absolute accuracy levels and nonlinearity errors previ- ously unattainable at a comparable price. the ad592 can be employed in applications between C25 c and +105 c where conventional temperature sensors (i.e., ther- mistor, rtd, thermocouple, diode) are currently being used. the inherent low cost of a monolithic integrated circuit in a plastic package, combined with a low total parts count in any given application, make the ad592 the most cost effective tem- perature transducer currently available. expensive linearization circuitry, precision voltage references, bridge components, resis- tance measuring circuitry and cold junction compensation are not required with the ad592. typical application areas include: appliance temperature sens- ing, automotive temperature measurement and control, hvac (heating/ventilating/air conditioning) system monitoring, indus- trial temperature control, thermocouple cold junction compen- sation, board-level electronics temperature diagnostics, temperature readout options in instrumentation, and tempera- ture correction circuitry for precision electronics. particularly useful in remote sensing applications, the ad592 is immune to voltage drops and voltage noise over long lines due to its high impedance current output. ad592s can easily be multiplexed; the signal current can be switched by a cmos multiplexer or the supply voltage can be enabled with a tri-state logic gate. the ad592 is available in three performance grades: the ad592an, ad592bn and ad592cn. all devices are pack- aged in a plastic to-92 case rated from C45 c to +125 c. per- formance is specified from C25 c to +105 c. ad592 chips are also available, contact the factory for details. * protected by patent no. 4,123,698. product highlights 1. with a single supply (4 v to 30 v) the ad592 offers 0.5 c temperature measurement accuracy. 2. a wide operating temperature range (C25 c to +105 c) and highly linear output make the ad592 an ideal sub- stitute for older, more limited sensor technologies (i.e., thermistors, rtds, diodes, thermocouples). 3. the ad592 is electrically rugged; supply irregularities and variations or reverse voltages up to 20 v will not damage the device. 4. because the ad592 is a temperature dependent current source, it is immune to voltage noise pickup and ir drops in the signal leads when used remotely. 5. the high output impedance of the ad592 provides greater than 0.5 c/v rejection of supply voltage drift and ripple. 6. laser wafer trimming and temperature testing insures that ad592 units are easily interchangeable. 7. initial system accuracy will not degrade significantly over time. the ad592 has proven long term performance and repeatability advantages inherent in integrated cir- cuit design and construction. 378 343 273 248 1?/ o k ?5 ?5 0 +70 +105 +125 temperature ? o c i out ??
ordering guide max cal max error max nonlinearity package model error @ +25 8 c C25 8 c to +105 8 c C25 8 c to +105 8 c option ad592cn 0.5 c 1.0 c 0.35 c to-92 ad592bn 1.0 c 2.0 c 0.4 c to-92 ad592an 2.5 c 3.5 c 0.5 c to-92 ad592Cspecifications ad592an ad592bn ad592cn model min typ max min typ max min typ max units accuracy calibration error @ +25 c 1 1.5 2.5 0.7 1.0 0.3 0.5 c t a = 0 c to +70 c error over temperature 1.8 3.0 0.8 1.5 0.4 0.8 c nonlinearity 2 0.15 0.35 0.1 0.25 0.05 0.15 c t a = C25 c to +105 c error over temperature 3 2.0 3.5 0.9 2.0 0.5 1.0 c nonlinearity 2 0.25 0.5 0.2 0.4 0.1 0.35 c output characteristics nominal current output @ +25 c (298.2k) 298.2 298.2 298.2 m a temperature coefficient 1 1 1 m a/ c repeatability 4 0.1 0.1 0.1 c long term stability 5 0.1 0.1 0.1 c/month absolute maximum ratings operating temperature C25 +105 C25 +105 C25 +105 c package temperature 6 C45 +125 C45 +125 C45 +125 c forward voltage (+ to C) 44 44 44 v reverse voltage (C to +) 20 20 20 v lead temperature (soldering 10 sec) 300 300 300 c power supply operating voltage range 4 30 4 30 4 30 v power supply rejection +4 v < v s < +5 v 0.5 0.5 0.5 c/v +5 v < v s < +15 v 0.2 0.2 0.2 c/v +15 v < v s < +30 v 0.1 0.1 0.1 c/v notes 1 an external calibration trim can be used to zero the error @ +25 c. 2 defined as the maximum deviation from a mathematically best fit line. 3 parameter tested on all production units at +105 c only. c grade at C25 c also. 4 maximum deviation between +25 c readings after a temperature cycle between C45 c and +125 c. errors of this type are noncumulative. 5 operation @ +125 c, error over time is noncumulative. 6 although performance is not specified beyond the operating temperature range, temperature excursions within the package temperature range will not damage the device. specifications subject to change without notice. specifications shown in boldface are tested on all production units at final electrical test. results from those tests are used to calculate outgoing quality levels. all min and max specifications are guaranteed, although only those shown in boldface are tested on all production units. (typical @ t a = +25 8 c, v s = +5 v, unless otherwise noted) temperature scale conversion equations metalization diagram 66mils 42mils v+ v rev. a C2C r = f +459.7 k = c +273.15 8 c = 5 9 ( 8 f C32) 8 f = 9 5 8 c +32
typical performance curvesCad592 typical @ v s = +5 v total error ? o c temperature ? o c ?5 0 +25 +70 +105 +2.0 +1.5 +1.0 +0.5 0 ?.5 ?.0 ?.5 ?.0 ad592cn accuracy over temperature +2.0 +1.5 +1.0 +0.5 0 ?.5 ?.0 ?.5 ?.0 ?5 0 +25 +70 +105 temperature ? o c total error ? o c ad592an accuracy over temperature total error ? o c temperature ? o c ?5 0 +25 +70 +105 +2.0 +1.5 +1.0 +0.5 0 ?.5 ?.0 ?.5 ?.0 ad592bn accuracy over temperature 0.75 0.50 0.25 0 ?.25 ?.50 ?.75 0 500 1000 1500 2000 time ?hours total error ? o c long-term stability @ +85 c and 85% relative humidity rev. a C3C 0.75 0.50 0.25 0 ?.25 ?.50 ?.75 0 500 1000 1500 2000 time ?hours total error ? o c long-term stability @ +125 c
ad592 rev. a C4C theory of operation the ad592 uses a fundamental property of silicon transistors to realize its temperature proportional output. if two identical transistors are operated at a constant ratio of collector current densities, r, then the difference in base-emitter voltages will be (kt/q)(ln r). since both k, boltzmans constant and q, the charge of an electron are constant, the resulting voltage is directly proportional to absolute temperature (ptat). in the ad592 this difference voltage is converted to a ptat current by low temperature coefficient thin film resistors. this ptat current is then used to force the total output current to be pro- portional to degrees kelvin. the result is a current source with an output equal to a scale factor times the temperature (k) of the sensor. a typical v-i plot of the circuit at +25 c and the temperature extremes is shown in figure 1. supply voltage ?volts 378 248 06 1 i out ?? 2345 298 +105 o c +25 o c ?5 o c up to 30v figure 1. v-i characteristics factory trimming of the scale factor to 1 m a/k is accomplished at the wafer level by adjusting the ad592s temperature reading so it corresponds to the actual temperature. during laser trim- ming the ic is at a temperature within a few degrees of 25 c and is powered by a 5 v supply. the device is then packaged and automatically temperature tested to specification. factors affecting ad592 system precision the accuracy limits given on the specifications page for the ad592 make it easy to apply in a variety of diverse applications. to calculate a total error budget in a given system it is impor- tant to correctly interpret the accuracy specifications, non- linearity errors, the response of the circuit to supply voltage variations and the effect of the surrounding thermal environ- ment. as with other electronic designs external component se- lection will have a major effect on accuracy. calibration error, absolute accuracy and nonlinearity specifications three primary limits of error are given for the ad592 such that the correct grade for any given application can easily be chosen for the overall level of accuracy required. they are the calibra- tion accuracy at +25 c, and the error over temperature from 0 c to +70 c and C25 c to +105 c. these specifications cor- respond to the actual error the user would see if the current out- put of an ad592 were converted to a voltage with a precision resistor. note that the maximum error at room temperature, over the commercial ic temperature range, or an extended range including the boiling point of water, can be directly read from the specifications table. all three error limits are a combi- nation of initial error, scale factor variation and nonlinearity de- viation from the ideal 1 m a/k output. figure 2 graphically depicts the guaranteed limits of accuracy for an ad592cn. temperature ? o c +1.0 +0.5 ?5 +105 0 +25 +70 0 ?.5 ?.0 total error ? o c maximum error over temperature typical error calibration error limit maximum error over temperature figure 2. error specifications (ad592cn) the ad592 has a highly linear output in comparison to older technology sensors (i.e., thermistors, rtds and thermo- couples), thus a nonlinearity error specification is separated from the absolute accuracy given over temperature. as a maxi- mum deviation from a best-fit straight line this specification rep- resents the only error which cannot be trimmed out. figure 3 is a plot of typical ad592cn nonlinearity over the full rated tem- perature range. typical nonlinearity +0.2 +0.1 ?5 +105 0 +25 +70 0 ?.1 ?.2 temperature ? o c nonlinearity ? o c figure 3. nonlinearity error (ad592cn) trimming for higher accuracy calibration error at 25 c can be removed with a single tempera- ture trim. figure 4 shows how to adjust the ad592s scale fac- tor in the basic voltage output circuit.
ad592 rev. a C5C +v ad592 r 100 w 950 w v out = 1mv/k figure 4. basic voltage output (single temperature trim) to trim the circuit the temperature must be measured by a ref- erence sensor and the value of r should be adjusted so the out- put (v out ) corresponds to 1 mv/k. note that the trim procedure should be implemented as close as possible to the temperature highest accuracy is desired for. in most applications if a single temperature trim is desired it can be implemented where the ad592 current-to-output voltage conversion takes place (e.g., output resistor, offset to an op amp). figure 5 illus- trates the effect on total error when using this technique. after single temperature calibration accuracy without trim +1.0 +0.5 ?5 +105 +25 0 ?.5 ?.0 temperature ? o c total error ? o c figure 5. effect of scale factor trim on accuracy if greater accuracy is desired, initial calibration and scale factor errors can be removed by using the ad592 in the circuit of figure 6. 8.66k w r1 1k w 97.6k w r2 5k w 7.87k w ad741 v out = 100mv/ o c +5v ad1403 v ad592 figure 6. two temperature trim circuit with the transducer at 0 c adjustment of r1 for a 0 v output nulls the initial calibration error and shifts the output from k to c. tweaking the gain of the circuit at an elevated temperature by adjusting r2 trims out scale factor error. the only error remaining over the temperature range being trimmed for is nonlinearity. a typical plot of two trim accuracy is given in figure 7. supply voltage and thermal environment effects the power supply rejection characteristics of the ad592 mini- mizes errors due to voltage irregularity, ripple and noise. if a supply is used other than 5 v (used in factory trimming), the power supply error can be removed with a single temperature trim. the ptat nature of the ad592 will remain unchanged. the general insensitivity of the output allows the use of lower cost unregulated supplies and means that a series resistance of several hundred ohms (e.g., cmos multiplexer, meter coil resistance) will not degrade the overall performance. +2.0 +1.0 ?5 +105 +25 0 ?.0 ?.0 temperature ? o c total error ? o c 0 +75 figure 7. typical two trim accuracy the thermal environment in which the ad592 is used deter- mines two performance traits: the effect of self-heating on accu- racy and the response time of the sensor to rapid changes in temperature. in the first case, a rise in the ic junction tempera- ture above the ambient temperature is a function of two vari- ables; the power consumption level of the circuit and the thermal resistance between the chip and the ambient environ- ment ( q ja ). self-heating error in c can be derived by multiply- ing the power dissipation by q ja . because errors of this type can vary widely for surroundings with different heat sinking capaci- ties it is necessary to specify q ja under several conditions. table i shows how the magnitude of self-heating error varies relative to the environment. in typical free air applications at +25 c with a 5 v supply the magnitude of the error is 0.2 c or less. a common clip-on heat sink will reduce the error by 25% or more in critical high temperature, large supply voltage situations. table i. thermal characteristics medium q ja ( c/watt) t (sec)* still air without heat sink 175 60 with heat sink 130 55 moving air without heat sink 60 12 with heat sink 40 10 fluorinert liquid 35 5 aluminum block** 30 2.4 notes * t is an average of five time constants (99.3% of final value). in cases where the thermal response is not a simple exponential function, the actual thermal re- sponse may be better than indicated. **with thermal grease.
ad592 rev. a C6C v t avg (1mv/k) ad592 +5v 333.3 w (0.1%) v t avg (10mv/k) 10k w (0.1%) +15v ad592 ad592 ad592 figure 9. average and minimum temperature connections the circuit of figure 10 demonstrates a method in which a voltage output can be derived in a differential temperature measurement. r1 50k w 10k w ad741 v out = (t 1 ?t 2 ) x (10mv/ o c) 10k w 5m w ? +v ad592 ad592 figure 10. differential measurements r1 can be used to trim out the inherent offset between the two devices. by increasing the gain resistor (10 k w ) temperature measurements can be made with higher resolution. if the magni- tude of v+ and vC is not the same, the difference in power con- sumption between the two devices can cause a differential self-heating error. cold junction compensation (cjc) used in thermocouple signal conditioning can be implemented using an ad592 in the circuit configuration of figure 11. expensive simulated ice baths or hard to trim, inaccurate bridge circuits are no longer required. ad op07e reference junction 100k w 10k w v out +7.5v measuring junction 1k w ad592 r thermocouple type approx. r value j k t e s r 52 w 41 w 41 w 61 w 6 w 6 w 2.5v ad1403 r g1 r g2 (1k w ) cu cu figure 11. thermocouple cold junction compensation response of the ad592 output to abrupt changes in ambient temperature can be modeled by a single time constant t expo- nential function. figure 8 shows typical response time plots for several media of interest. percent of final temperature time ?sec 100 80 60 50 40 30 20 10 90 70 a b c d e f 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 a aluminum block b fluorinert liquid c moving air (with heat sink) d moving air (without heat sink) e still air (with heat sink) f still air (without heat sink) figure 8. thermal response curves the time constant, t , is dependent on q ja and the thermal ca- pacities of the chip and the package. table i lists the effective t (time to reach 63.2% of the final value) for several different media. copper printed circuit board connections where ne- glected in the analysis, however, they will sink or conduct heat directly through the ad592s solder dipped kovar leads. when faster response is required a thermally conductive grease or glue between the ad592 and the surface temperature being mea- sured should be used. in free air applications a clip-on heat sink will decrease output stabilization time by 10-20%. mounting considerations if the ad592 is thermally attached and properly protected, it can be used in any temperature measuring situation where the maximum range of temperatures encountered is between C25 c and +105 c. because plastic ic packaging technology is em- ployed, excessive mechanical stress must be safeguarded against when fastening the device with a clamp or screw-on heat tab. thermally conductive epoxy or glue is recommended under typical mounting conditions. in wet or corrosive environments, any electrically isolated metal or ceramic well can be used to shield the ad592. condensation at cold temperatures can cause leakage current related errors and should be avoided by sealing the device in nonconductive epoxy paint or dips. applications connecting several ad592 devices in parallel adds the currents through them and produces a reading proportional to the aver- age temperature. series ad592s will indicate the lowest tem- perature because the coldest device limits the series current flowing through the sensors. both of these circuits are depicted in figure 9.
ad592 rev. a C7C the circuit shown can be optimized for any ambient tempera- ture range or thermocouple type by simply selecting the correct value for the scaling resistor C r. the ad592 output (1 m a/k) times r should approximate the line best fit to the thermocouple curve (slope in v/ c) over the most likely ambient temperature range. additionally, the output sensitivity can be chosen by selecting the resistors r g1 and r g2 for the desired noninverting gain. the offset adjustment shown simply references the ad592 to c. note that the tcs of the reference and the resistors are the primary contributors to error. temperature rejection of 40 to 1 can be easily achieved using the above technique. although the ad592 offers a noise immune current output, it is not compatible with process control/industrial automation cur- rent loop standards. figure 12 is an example of a temperature to 4C20 ma transmitter for use with 40 v, 1 k w systems. in this circuit the 1 m a/k output of the ad592 is amplified to 1 ma/ c and offset so that 4 ma is equivalent to 17 c and 20 ma is equivalent to 33 c. rt is trimmed for proper reading at an intermediate reference temperature. with a suitable choice of resistors, any temperature range within the operating limits of the ad592 may be chosen. ad592 ad581 35.7k w 10mv/ o c 10k w 12.7k w 5k w 500 w +20v ?0v v t 10 w c r t 5k w 1ma/ o c 208 17 c ? 4ma 33 c ? 20? figure 12. temperature to 4C20 ma current transmitter reading temperature with an ad592 in a microprocessor based system can be implemented with the circuit shown in figure 13. ad1403 950 w 9k w 1k w 100 w +5v ad592 span trim center point trim format bpo/upo 200 w ? control gnd v in hi v i hi n v i lo n v i lo n 8 bits out ad670 adcport r/w cs ce v cc figure 13. temperature to digital output by using a differential input a/d converter and choosing the current to voltage conversion resistor correctly, any range of temperatures (up to the 130 c span the ad592 is rated for) centered at any point can be measured using a minimal number of components. in this configuration the system will resolve up to 1 c. a variable temperature controlling thermostat can easily be built using the ad592 in the circuit of figure 14. ad592 10k w r hyst r pull-up +15v comparator (optional) c r high 62.7k w r set 10k w c temp > setpoint output high temp < setpoint output low r low 27.3k w ad581 figure 14. variable temperature thermostat r high and r low determine the limits of temperature controlled by the potentiometer r set . the circuit shown operates over the full temperature range (C25 c to +105 c) the ad592 is rated for. the reference maintains a constant set point voltage and insures that approximately 7 v appears across the sensor. if it is necessary to guardband for extraneous noise hysteresis can be added by tying a resistor from the output to the ungrounded end of r low. multiple remote temperatures can be measured using several ad592s with a cmos multiplexer or a series of 5 v logic gates because of the devices current-mode output and supply-voltage compliance range. the on-resistance of a fet switch or output impedance of a gate will not affect the accuracy, as long as 4 v is maintained across the transducer. muxs and logic driving circuits should be chosen to minimize leakage current related errors. figure 15 illustrates a locally controlled mux switching the signal current from several remote ad592s. cmos or ttl gates can also be used to switch the ad592 supply voltages, with the multiplexed signal being transmitted over a single twisted pair to the load. ad7501 d e c o d e r / d r i v e r t 8 t 2 t 1 remote ad592s s1 s2 s8 e n ttl dtl to cmos i/o channel select +15v ?5v v out 10k w figure 15. remote temperature multiplexing
ad592 rev. a C8C to minimize the number of muxs required when a large num- ber of ad592s are being used, the circuit can be configured in a matrix. that is, a decoder can be used to switch the supply volt- age to a column of ad592s while a mux is used to control which row of sensors are being measured. the maximum num- ber of ad592s which can be used is the product of the number of channels of the decoder and mux. an example circuit controlling 80 ad592s is shown in figure 16. a 7-bit digital word is all that is required to select one of the sensors. the enable input of the multiplexer turns all the sensors off for minimum dissipation while idling. +15v column select 4028 bcd to decimal decoder row select e n +15v ?5v 80 ?ad592s 10k w v out ad7501 8-channel mux figure 16. matrix multiplexer to convert the ad592 output to c or f a single inexpensive reference and op amp can be used as shown in figure 17. al- though this circuit is similar to the two temperature trim circuit shown in figure 6, two important differences exist. first, the gain resistor is fixed alleviating the need for an elevated tem- perature trim. acceptable accuracy can be achieved by choosing an inexpensive resistor with the correct tolerance. second, the ad592 calibration error can be trimmed out at a known conve- nient temperature (i.e., room temperature) with a single pot ad- justment. this step is independent of the gain selection. r r offset /r gain ad741 v out = 100mv/( o c or o f) +5v ad1403 v o c o f ? 9.1k w ? 9.8k w 100k w 180k w r gain r offset ad592 r cal 2.5v r gain r offset figure 17. celsius or fahrenheit thermometer printed in u.s.a. c819bC2C7/93 outline dimensions dimensions shown in inches and (mm). 0.105 (2.66) 0.080 (2.42) 0.105 (2.66) 0.080 (2.42) 0.165 (4.19) 0.125 (3.94) square 0.019 (0.482) 0.016 (0.407) 0.105 (2.66) 0.095 (2.42) 0.055 (1.39) 0.045 (1.15) seating plane 0.500 (12.70) min 0.205 (5.20) 0.175 (4.96) 0.210 (5.33) 0.170 (4.32) 123 bottom view 0.135 (3.43) min 0.050 (1.27) max
analog products -- ad592 page 1 of 1 file://f:\export\projects\bitting2\imaging\bitting\mail_pdf\200\models9.html 5/8/01 package/price information for detailed packaging information, please select the datasheets button. low cost, precision ic temperature transducer * this price is provided for budgetary purposes as recommended list price in u.s. dollars per unit the stated volume. pricing displayed for evaluation boards and kits is based on 1-piece pricing. view pricing and availability (currently available to north american customers) for further information. ?model? status package description pin count temperature range price* (100- 499) ?AD592ACHIPS? ?production? ?chips/die sales? - ?commercial? ?$2.08? ?ad592an? ?production? ?to-92 transistor-style pkg? ?3? ?commercial? ?$2.21? ?ad592bn? ?production? ?to-92 transistor-style pkg? ?3? ?commercial? ?$6.87? ?ad592cn? ?production? ?to-92 transistor-style pkg? ?3? ?commercial? ?$9.16?
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