AD597AHZ

(@ +608C and VS = 10 V, Type J (AD596), Type K (AD597) Thermocouple, AD596/AD597–SPECIFICATIONS unless otherwise noted) Model AD596AH Typ Max Min ABSOLUTE MAXIMUM RATINGS +VS to –VS Common-Mode Input Voltage Differential Input Voltage Alarm Voltages +ALM –ALM Operating Temperature Range Output Short Circuit to Common TEMPERATURE MEASUREMENT (Specified Temperature Range +25°C to +100°C) Calibration Error1 Stability vs. Temperature2 Gain Error Nominal Transfer Function AMPLIFIER CHARACTERISTICS Closed Loop Gain3 Input Offset Voltage Input Bias Current Differential Input Range Common-Mode Range Common-Mode Sensitivity–RTO Power Supply Sensitivity–RTO Output Voltage Range Dual Supplies Single Supply Usable Output Current4 3 dB Bandwidth (–VS – 0.15) –VS –VS –VS –55 Indefinite –4 ± 0.02 –1.5 36 +VS +VS AD597AH Typ Min (–VS – 0.15) –VS (–VS +36) +VS +125 –VS –VS –55 Indefinite +4 ± 0.05 +1.5 –4 ± 0.02 –1.5 10 Min 36 +VS +VS (–VS – 0.15) –VS (–VS +36) +VS +125 –VS –VS –40 Indefinite +4 ± 0.05 +1.5 –4 POWER REQUIREMENTS Operating Quiescent Current +VS –VS –1.5 (+VS – 2) (+VS – 2) 245.5 °C × 41.27 – 37 0.1 –10 (+VS – 0.15) 1 (–VS + 2.5) 0 ±5 Max Units 36 +VS +VS Volts Volts Volts (–VS +36) +VS +125 Volts Volts °C +4 ± 0.05 +1.5 °C °C/°C % mV/°C 10 245.5 °C × 41.27 – 37 0.1 +50 (+VS – 4) 10 10 –10 (–VS – 0.15) (+VS – 2) (+VS – 2) (–VS + 2.5) 0 ±5 1 15 +50 (+V S – 4) 10 10 (+VS – 2) (+VS – 2) 15 5 ALARM CHARACTERISTICS VCE(SAT) at 2 mA Leakage Current Operating Voltage at – ALM Short Circuit Current ± 0.02 10 180.6 °C × 53.21 + 235 0.1 –10 +50 (–VS – 0.15) (+V S – 4) 10 1 10 (–VS + 2.5) 0 ±5 15 AD597AR Typ Max V/V µV µA mV Volts mV/V mV/V Volts Volts mA kHz Alarm Function Not Pinned Out 0.3 0.3 61 (+VS – 4) 20 20 (+VS to –VS) ≤ 30 160 100 Volts µA Volts mA 61 (+VS – 4) (+VS to –VS) ≤ 30 (+VS to –VS) ≤ 30 160 100 160 100 300 200 300 200 300 200 Volts µA µA NOTES 1 This is a measure of the deviation from ideal with a measuring thermocouple junction of 175°C and a chip temperature of 60°C. The ideal transfer function is given by: AD596: VOUT = 180.57 × (Vm – Va + (ambient in °C) × 53.21 µV/°C + 235 µV) AD597: VOUT = 245.46 × (Vm – Va + (ambient in °C) × 41.27 µV/°C – 37 µV) where Vm , and Va represent the measuring and ambient temperatures and are taken from the appropriate J or K thermocouple table. The ideal transfer function minimizes the error over the ambient temperature range of 25°C to 100°C with a thermocouple temperature of approximately 175°C. 2 Defined as the slope of the line connecting the AD596/AD597 CJC errors measured at 25°C and 100°C ambient temperature. 3 Pin 6 shorted to Pin 7. 4 Current Sink Capability in single supply configuration is limited to current drawn to ground through a 50 kΩ resistor at output voltages below 2.5 V. 5 Alarm function available on H package option only. 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. ORDERING GUIDE Model Package Description Package Options AD596AH AD597AH AD597AR* TO-100 TO-100 Plastic SOIC H-10A H-10A SO-8 *Consult factory for availability. –2– REV. B AD596/AD597 Table I. Output Voltage vs. Thermocouple Temperature (Ambient +608C, VS = –5 V, +15 V) Thermocouple Temperature 8C Type J Voltage mV AD596 Output mV Type K Voltage mV Type J Voltage mV AD596 Output mV Type K Voltage mV AD597 Output mV –200 –180 –160 –140 –120 –7.890 –7.402 –6.821 –6.159 –5.426 –1370 –1282 –1177 –1058 –925 –5.891 –5.550 –5.141 –4.669 –4.138 –1446 –1362 –1262 –1146 –1016 500 520 540 560 580 27.388 28.511 29.642 30.782 31.933 5000 5203 5407 5613 5821 20.640 21.493 22.346 23.198 24.050 5066 5276 5485 5694 5903 –100 –80 –60 –40 –20 –4.632 –3.785 –2.892 –1.960 –.995 –782 –629 –468 –299 –125 –3.553 –2.920 –2.243 –1.527 –.777 –872 –717 –551 –375 –191 600 620 640 660 680 33.096 34.273 35.464 36.671 37.893 6031 6243 6458 6676 6897 24.902 25.751 26.599 27.445 28.288 6112 6321 6529 6737 6944 –10 0 10 20 25 –.501 0 .507 1.019 1.277 –36 54 146 238 285 –.392 0 .397 .798 1.000 –96 0 97 196 245 700 720 740 750 760 39.130 40.382 41.647 42.283 – 7120 7346 7575 7689 – 29.128 29.965 30.799 31.214 31.629 7150 7355 7560 7662 7764 30 40 50 60 80 1.536 2.058 2.585 3.115 4.186 332 426 521 617 810 1.203 1.611 2.022 2.436 3.266 295 395 496 598 802 780 800 820 840 860 – – – – – – – – – – 32.455 33.277 34.095 34.909 35.718 7966 8168 8369 8569 8767 100 120 140 160 180 5.268 6.359 7.457 8.560 9.667 1006 1203 1401 1600 1800 4.095 4.919 5.733 6.539 7.338 1005 1207 1407 1605 1801 880 900 920 940 960 – – – – – – – – – – 36.524 37.325 38.122 38.915 39.703 8965 9162 9357 9552 9745 200 220 240 260 280 10.777 11.887 12.998 14.108 15.217 2000 2201 2401 2602 2802 8.137 8.938 9.745 10.560 11.381 1997 2194 2392 2592 2794 980 1000 1020 1040 1060 – – – – – – – – – – 40.488 41.269 42.045 42.817 43.585 9938 10130 10320 10510 10698 300 320 340 360 380 16.325 17.432 18.537 19.640 20.743 3002 3202 3402 3601 3800 12.207 13.039 13.874 14.712 15.552 2996 3201 3406 3611 3817 1080 1100 1120 1140 1160 – – – – – – – – – – 44.439 45.108 45.863 46.612 47.356 10908 11072 11258 11441 11624 400 420 440 460 480 21.846 22.949 24.054 25.161 26.272 3999 4198 4398 4598 4798 16.395 17.241 18.088 18.938 19.788 4024 4232 4440 4649 4857 1180 1200 1220 1240 1250 – – – – – – – – – – 48.095 48.828 49.555 50.276 50.633 11805 11985 12164 12341 12428 REV. B AD597 Output mV Thermocouple Temperature 8C –3– AD596/AD597 Excluding calibration errors, the above transfer function is accurate to within 1°C from +80°C to +550°C for the AD596 and –20°C to +350°C for the AD597. The different temperature ranges are due to the differences in J and K type thermocouple curves. TEMPERATURE PROPORTIONAL OUTPUT MODE The AD596/AD597 can be used to generate a temperature proportional output of 10 mV/°C when operated with J and K type thermocouples as shown in Figure 1. Thermocouples produce low level output voltages which are a function of both the temperature being measured and the reference or cold junction temperature. The AD596/AD597 compensates for the cold junction temperature and amplifies the thermocouple signal to produce a high level 10 mV/°C voltage output which is a function only of the temperature being measured. The temperature stability of the part indicates the sensitivity of the output voltage to changes in ambient or device temperatures. This is typically 0.02°C/°C over the +25°C to +100°C recommended ambient temperature range. The parts will operate over the extended ambient temperature ranges from –55°C to +125°C, but thermocouple nonlinearity at the reference junction will degrade the temperature stability over this extended range. Table I is a list of ideal AD596/AD597 output voltages as a function of Celsius temperature for type J and K ANSI standard thermocouples with package and reference junction at 60°C. As is normally the case, these outputs are subject to calibration and temperature sensitivity errors. These tables are derived using the ideal transfer functions: European DIN FE-CuNi thermocouple vary slightly from ANSI type J thermocouples. Table I does not apply when these types of thermocouples are used. The transfer functions given previously and a thermocouple table should be used instead. Figure 1 also shows an optional trimming network which can be used to change the device’s offset voltage. Injecting or sinking 200 nA from Pin 3 will offset the output approximately 10 mV (1°C). The AD596/AD597 can operate from a single supply from 5 V to 36 V or from split supplies totalling 36 V or less as shown. Since the output can only swing to within 2 V of the positive supply, the usable measurement temperature range will be restricted when positive supplies less than 15 V for the AD597 and 10 V for the AD596 are used. If the AD596/AD597 is to be used to indicate negative Celsius temperatures, then a negative supply is required. Common-mode voltages on the thermocouple inputs must remain within the common-mode voltage range of the AD596/ AD597, with a return path provided for the bias currents. If the thermocouple is not remotely grounded, then the dotted line connection shown in Figure 1 must be made to one of the thermocouple inputs. If there is no return path for the bias currents, the input stage will saturate, causing erroneous output voltages. AD596 output = (Type J voltage + 301.5 µV) × 180.57 AD597 output = (Type K voltage) × 245.46 CONSTANTAN (ALUMEL) IRON (CHROMEL) +5V TO +30V AD596/ AD597* +15V 100kV OPTIONAL OFFSET 10kV ADJUST 100kV VOUT SPAN OF +5V TO +30V 1MV –15V In this configuration, the AD596/AD597 H package option has circuitry which detects the presence of an open thermocouple. If the thermocouple loop becomes open, one or both of the inputs to the device will be deprived of bias current causing the output to saturate. It is this saturation which is detected internally and used to activate the alarm circuitry. The output of this feature has a flexible format which can be used to source or sink up to 20 mA of current. The collector (+ALM) should not be allowed to become more positive than (–VS + 36 V), however, it may be permitted to be more positive than +VS. The emitter voltage (–ALM) should be constrained such that it does not become more positive than 4 V below +VS. If the alarm feature is not used, this pin should be connected to Pins 4 or 5 as shown in Figure 1. The alarm function is unavailable on the AR package option. 0.01mF 0.01mF 0 TO –25V *H PACKAGE PINOUT SHOWN Figure 1. Temperature Proportional Output Connection The offsets and gains of these devices have been laser trimmed to closely approximate thermocouple characteristics over measurement temperature ranges centered around 175°C with the AD596/AD597 at an ambient temperature between 25°C and 100°C. This eliminates the need for additional gain or offset adjustments to make the output voltage read: VOUT = 10 mV/°C × (thermocouple temperature in °C) (within specified tolerances). –4– REV. B AD596/AD597 SETPOINT CONTROL MODE The AD596/AD597 can be connected as a setpoint controller as shown in Figure 2. The thermocouple voltage is cold junction compensated, amplified, and compared to an external setpoint voltage. The relationship between setpoint voltage and temperature is given in Table I. If the temperature to be controlled is within the operating range (–55°C to +125°C) of the device, it can monitor its own temperature by shorting the inputs to ground. The setpoint voltage with the thermocouple inputs grounded is given by the expressions: +VS – G + 0.01mF ICE POINT COMP – G + + +A AD596/ AD597* AD596 Setpoint Voltage = °C × 9.6 mV/°C + 42 mV AD597 Setpoint Voltage = °C × 10.1 mV/°C – 9.1 mV *H PACKAGE PINOUT SHOWN The input impedance of the setpoint pin of the AD596/AD597 is approximately 50 kΩ. The temperature coefficient of this resistance is ± 15 ppm/°C. Therefore, the 100 ppm/°C 5 kΩ pot shown in Figure 2 will only introduce an additional ± 1°C degradation of temperature stability over the +25°C to +100°C ambient temperature range. TEMPERATURE CONTROLLED CONSTANTAN (ALUMEL) REGION R VREF SETPOINT VOLTAGE SETPOINT VOLTAGE 5kV 100ppm/8C HYSTERESIS (OPTIONAL) HEATER DRIVER *H PACKAGE PINOUT SHOWN Figure 2. Setpoint Control Mode Switching hysteresis is often used in setpoint systems of this type to provide noise immunity and increase system reliability. By reducing the frequency of on-off cycling, mechanical component wear is reduced leading to enhanced system reliability. This can easily be implemented with a single external resistor between Pins 7 and 3 of the AD596/AD597. Each 200 nA of current injected into Pin 3 when the output switches will cause about 1°C of hysteresis; that is: RHYST (Ω) = 0.01mF –VS Figure 3. Stand-Alone Temperature Transducer Temperature Proportional Output Connection TEMPERATURE COMPARATOR 0.01mF OUTPUT +V AD596/ AD597* IRON (CHROMEL) Simply omit the thermocouple and connect the inputs (Pins 1 and 2) to common. The output will now reflect the compensation voltage and hence will indicate the AD596/AD597 temperature. In this three terminal, voltage output, temperature sensing mode, the AD596/AD597 will operate over the full extended –55°C to +125°C temperature range. The output scaling will be 9.6 mV per °C with the AD596 and 10.1 mV per °C with the AD597. Additionally there will be a 42 mV offset with the AD596 causing it to read slightly high when used in this mode. THERMOCOUPLE CONNECTIONS The connection of the thermocouple wire and the normal wire or printed circuit board traces going to the AD596/AD597 forms an effective reference junction as shown in Figure 4. This junction must be kept at the same temperature as the AD596/ AD597 for the internal cold junction compensation to work properly. Unless the AD596/AD597 is in a thermally stable enclosure, the thermocouple leads should be brought in directly to Pins 1 and 2. REFERENCE JUNCTION LIMITING RESISTOR TO LED 0.01mF CONSTANTAN (ALUMEL) IRON +VS (CHROMEL) AD596/ AD597* NOTE: A BIAS RETURN PATH FROM PINS 1 AND 2 OF LESS THAN 1kV IMPEDANCE MUST BE PROVIDED. V OUT 1 × 200 nA °CHYST VOUT In the setpoint configuration, the AD596/AD597 output is saturated at all times, so the alarm transistor will be ON regardless of whether there is an open circuit or not. However, –ALM must be tied to a voltage below (+VS – 4 V) for proper operation of the rest of the circuit. 0.01mF *H PACKAGE PINOUT SHOWN STAND-ALONE TEMPERATURE TRANSDUCER The AD596/AD597 may be configured as a stand-alone Celsius thermometer as shown in Figure 3. REV. B VOUT 9.6mV/8C GND –VS Figure 4. PCB Connections To ensure secure bonding, the thermocouple wire should be cleaned to remove oxidization prior to soldering. Noncorrosive resin flux is effective with iron, constantan, chromel, and alumel, and the following solders: 95% tin–5% silver, or 90% tin–10% lead. –5– AD596/AD597 temperature differences will result in a direct error at the output. In the temperature proportional mode, the alarm feature will only activate in the event of an open thermocouple or system transient which causes the device output to saturate. Self-Heating errors will not effect the operation of the alarm but two cases do need to be considered. First, after a fault is corrected and the alarm is reset, the AD596/AD597 must be allowed to cool before readings can again be accurate. This can take 5 minutes or more depending upon the thermal environment seen by the device. Second, the junction temperature of the part should not be allowed to exceed 150°C. If the alarm circuit of the AD596/AD597 is made to source or sink 20 mA with 30 V across it, the junction temperature will be 90°C above ambient causing the die temperature to exceed 150°C when ambient is above 60°C. In this case, either the load must be reduced, or a heat sink used to lower the thermal resistance. SINGLE AND DUAL SUPPLY CONNECTIONS In the single supply configuration as used in the setpoint controller of Figure 2, any convenient voltage from +5 V to +36 V may be used, with self-heating errors being minimized at lower supply levels. In this configuration, the –VS connection at Pin 5 is tied to ground. Temperatures below zero can be accommodated in the single supply setpoint mode, but not in the single supply temperature measuring mode (Figure 1 reconnected for single supply). Temperatures below zero can only be indicated by a negative output voltage, which is impossible in the single supply mode. Common-mode voltages on the thermocouple inputs must remain below the positive supply, and not more than 0.15 V more negative than the minus supply. In addition, a return path for the input bias currents must be provided. If the thermocouple is not remotely grounded, then the dotted line connections in Figures 1 and 2 are mandatory. TEMPERATURE READOUT AND CONTROL Figure 6 shows a complete temperature indication and control system based on the AD596/AD597. Here the AD596/AD597 is being used as a closed-loop thermocouple signal conditioner and an external op amp is used to implement setpoint. This has two important advantages. It provides a high level (10 mV/°C) output for the A/D panel meter and also preserves the alarm function for open thermocouples. STABILITY OVER TEMPERATURE The AD596/AD597 is specified for a maximum error of ± 4°C at an ambient temperature of 60°C and a measuring junction temperature at 175°C. The ambient temperature stability is specified to be a maximum of 0.05°C/°C. In other words, for every degree change in the ambient temperature, the output will change no more than 0.05 degrees. So, at 25°C the maximum deviation from the temperature-voltage characteristic of Table I is ± 5.75°C, and at 100°C it is ± 6°C maximum (see Figure 5). If the offset error of ± 4°C is removed with a single offset adjustment, these errors will be reduced to ± 1.75°C and ± 2°C max. The optional trim circuit shown in Figure 1 demonstrates how the ambient offset error can be adjusted to zero. The A/D panel meter can easily be offset and scaled as shown to read directly in degrees Fahrenheit. If a two temperature calibration scheme is used, the dominant residual errors will arise from two sources; the ambient temperature rejection (typically ± 2°C over a 25°C to 100°C range) and thermocouple nonlinearity typical +1°C from 80°C to 550°C for type J and +1°C from –20°C to 350°C for type K. An external voltage reference is used both to increase the stability of the A/D converter and supply a stable reference for the setpoint voltage. +2.08C +1.758C MAXIMUM A traditional requirement for the design of setpoint control thermocouple systems has been to configure the system such that the appropriate action is taken in the event of an open thermocouple. The open thermocouple alarm pin with its flexible current-limited output format supports this function when the part operates in the temperature proportional mode. In addition, if the thermocouple is not remotely grounded, it is possible to program the device for either a positive or negative full-scale output in the event of an open thermocouple. This is done by connecting the bias return resistor directly to Pin 1 if a high output voltage is desired to indicate a fault condition. Alternately, if the bias return is provided on the thermocouple lead connected to Pin 2, an open circuit will result in an output low reading. Figure 6 shows the ground return connected to Pin 1 so that if the thermocouple fails, the heater will remain off. At the same time, the alarm circuit lights the LED signalling the need to service the thermocouple. Grounding Pin 2 would lead to low output voltage saturation, and in this circuit would result in a potentially dangerous thermal runaway under fault conditions. +0.88C 0 TYPICAL –0.88C MAXIMUM –1.758C –2.08C 258C 608C 1008C Figure 5. Drift Error vs. Temperature THERMAL ENVIRONMENTAL EFFECTS The inherent low power dissipation of the AD596/AD597 keeps self-heating errors to a minimum. However, device output is capable of delivering ± 5 mA to an external load and the alarm circuitry can supply up to 20 mA. Since the typical junction to ambient thermal resistance in free air is 150°C/W, significant temperature difference between the package pins (where the reference junction is located) and the chip (where the cold junction temperature is measured and then compensated) can exist when the device is operated in a high dissipation mode. These –6– REV. B AD596/AD597 +V TEMPERATURE CONSTANTAN (ALUMEL) IRON (CHROMEL) READOUT 8F 470V – LCD DISPLAY + +V AD596/ AD597* HEATER ICL7136 45.2kV IN HI 10kV IN LO 1.27MV +V *H PACKAGE PINOUT SHOWN 5V 40.2kV REF HI AD584 10kV REF LO SET-POINT ADJUST 5kV – 10kV 1kV OP07 + 10MV Figure 6. Temperature Measurement and Control REV. B –7– 120V AC AD596/AD597 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 10-Pin Metal Can (TO-100) 0.185 (4.70) 0.165 (4.19) 0.160 (4.06) 0.110 (2.79) 0.250 (6.35) MIN 0.050 (1.27) MAX 6 7 0.370 (9.40) 0.335 (8.51) 0.335 (8.51) 0.305 (7.75) 5 0.115 (2.92) BSC C831b–5–2/98 REFERENCE PLANE 0.750 (19.05) 0.500 (12.70) 8 4 0.045 (1.14) 0.027 (0.69) 9 3 2 0.019 (0.48) 0.016 (0.41) 10 1 0.230 (5.84) BSC 0.021 (0.53) 0.016 (0.41) 0.040 (1.02) MAX 0.045 (1.14) 0.010 (0.25) 0.034 (0.86) 0.027 (0.69) 36° BSC BASE & SEATING PLANE 8-Lead Small Outline (SOIC) (SO-8) 0.1968 (5.00) 0.1890 (4.80) 0.1574 (4.00) 0.1497 (3.80) PIN 1 0.0098 (0.25) 0.0040 (0.10) 8 5 1 4 0.2440 (6.20) 0.2284 (5.80) 0.0688 (1.75) 0.0532 (1.35) 8° 0° 0.0500 (1.27) 0.0160 (0.41) PRINTED IN U.S.A. 0.0500 0.0192 (0.49) SEATING (1.27) 0.0098 (0.25) PLANE BSC 0.0138 (0.35) 0.0075 (0.19) 0.0196 (0.50) x 45° 0.0099 (0.25) –8– REV. B