Analog Devices AD597, AD596 Datasheet

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Thermocouple Conditioner and

FEATURES Low Cost Operates with Type J (AD596) or Type K (AD597)

Thermocouples Built-In Ice Point Compensation Temperature Proportional Operation – 10 mV/8C Temperature Setpoint Operation – ON/OFF Programmable Switching Hysteresis High Impedance Differential Input

GENERAL DESCRIPTION

The AD596/AD597 is a monolithic temperature setpoint controller that has been optimized for use at elevated temperatures such as those found in oven control applications. The device cold junction compensates and amplifies a type J or K thermocouple input to derive an internal signal proportional to temperature. The internal signal is then compared with an externally applied setpoint voltage to yield a low impedance switched output voltage. Dead-Band or switching hysteresis can be programmed using a single external resistor. Alternately, the AD596/AD597 can be configured to provide a voltage output (10 mV/°C) directly from a type J or K thermocouple signal. It can also be used as a standalone voltage output temperature sensor.

The AD596/AD597 can be powered with a single supply from +5 V to +30 V, or dual supplies up to a total span of 36 V. Typical quiescent supply current is 160 µA, which minimizes self-heating errors.

The AD596/AD597 H package option includes a thermocouple failure alarm that indicates an open thermocouple lead when operated in the temperature proportional measurement mode. The alarm output has a flexible format which can be used to drive relays, LEDs or TTL logic.

The device is packaged in a reliability qualified, cost effective 10-pin metal can or SOIC and is trimmed to operate over an ambient temperature range from +25°C to +100°C. Operation over an extended ambient temperature range is possible with slightly reduced accuracy. The AD596 will amplify thermocouple signals covering the entire –200°C to +760°C temperature range recommended for type J thermocouples while the AD597 can accommodate –200°C to +1250°C type K inputs.

The AD596/AD597 has a calibration accuracy of ±4°C at an ambient temperature of 60°C and an ambient temperature stability specification of 0.05°C/°C from +25°C to +100°C. If higher accuracy, or a lower ambient operating temperature is required, either the AD594 (J thermocouple) or AD595 (K thermocouple) should be considered.

*Protected by U.S. Patent No. 4,029,974.

Setpoint Controller

AD596*/AD597*

FUNCTIONAL BLOCK DIAGRAM

TO-100

–ALM

AD596/

AD597

–

+ALM

V+

OUT

–IN

V+

OUT

–IN

–

+IN

HYS

ICE POINT COMP

GND

–

V–

SOIC

AD597

+IN

HYS

GND

V–

ICE POINT

COMP

TOP VIEW

(Not to Scale)

PRODUCT HIGHLIGHTS

1. The AD596/AD597 provides cold junction compensation and a high gain amplifier which can be used as a setpoint comparator.

2. The input stage of the AD596/AD597 is a high quality instrumentation amplifier that allows the thermocouple to float over most of the supply voltage range.

3. Linearization not required for thermocouple temperatures close to 175°C (+100°C to +540°C for AD596).

4. Cold junction compensation is optimized for ambient temperatures ranging from +25°C to +100°C.

5. In the stand-alone mode, the AD596/AD597 produces an output voltage that indicates its own temperature.

REV. B

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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 1998

AD596/AD597–SPECIFICA TIONS

(@ +608C and VS = 10 V, Type J (AD596), Type K (AD597) Thermocouple, unless otherwise noted)

Model AD596AH AD597AH AD597AR

Min Typ Max Min Typ Max Min Typ Max Units

ABSOLUTE MAXIMUM RATINGS

+VS to –V Common-Mode Input Voltage (–VS – 0.15) +V Differential Input Voltage –V Alarm Voltages

Operating Temperature Range –55 +125 –55 +125 –40 +125 °C

+ALM –V –ALM –V

S S

36 36 36 Volts +V

S S

(–VS – 0.15) +V –V

(–VS +36) –V +V

–V

S S

(–VS +36) –V +V

(–VS – 0.15) +V –V

–V

S S

+V (–VS +36) Volts

S S

Volts Volts

Volts

Output Short Circuit to Common Indefinite Indefinite Indefinite

TEMPERATURE MEASUREMENT

(Specified Temperature Range +25°C to +100°C)

Calibration Error Stability vs. Temperature

–4 +4 –4 +4 –4 +4 °C

± 0.02 ± 0.05 ± 0.02 ± 0.05 ± 0.02 ± 0.05 °C/°C

Gain Error –1.5 +1.5 –1.5 +1.5 –1.5 +1.5 % Nominal Transfer Function 10 10 10 mV/°C

AMPLIFIER CHARACTERISTICS

Closed Loop Gain

180.6 245.5 245.5 V/V Input Offset Voltage °C × 53.21 + 235 °C × 41.27 – 37 °C × 41.27 – 37 µV Input Bias Current 0.1 0.1 0.1 µA Differential Input Range –10 +50 –10 +50 –10 +50 mV Common-Mode Range (–VS – 0.15) (+VS – 4) (+VS – 0.15) (+VS – 4) (–VS – 0.15) (+VS – 4) Volts Common-Mode Sensitivity–RTO 10 10 10 mV/V Power Supply Sensitivity–RTO 1 10 1 10 1 10 mV/V Output Voltage Range

Dual Supplies (–VS + 2.5) (+VS – 2) (–VS + 2.5) (+VS – 2) (–VS + 2.5) (+VS – 2) Volts Single Supply 0 (+VS – 2) 0 (+VS – 2) 0 (+VS – 2) Volts

Usable Output Current

± 5 ± 5 ± 5mA

3 dB Bandwidth 15 15 15 kHz

ALARM CHARACTERISTICS

at 2 mA 0.3 0.3 Volts

CE(SAT)

Leakage Current 61 61 µA

Alarm Function Not Pinned Out

Operating Voltage at – ALM (+VS – 4) (+VS – 4) Volts Short Circuit Current 20 20 mA

POWER REQUIREMENTS

Operating (+VS to –VS) ≤ 30 (+VS to –VS) ≤ 30 (+VS to –VS) ≤ 30 Volts Quiescent Current

–V

NOTES

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: V AD597: V where V error over the ambient temperature range of 25°C to 100°C with a thermocouple temperature of approximately 175°C.

Defined as the slope of the line connecting the AD596/AD597 CJC errors measured at 25°C and 100°C ambient temperature.

Pin 6 shorted to Pin 7.

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.

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

= 180.57 × (Vm – Va + (ambient in °C) × 53.21 µV/°C + 235 µV)

OUT

= 245.46 × (Vm – Va + (ambient in °C) × 41.27 µV/°C – 37 µV)

OUT

, 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

160 300 160 300 160 300 µA 100 200 100 200 100 200 µA

are tested on all production units.

ORDERING GUIDE

Model Package Description Package Options

AD596AH TO-100 H-10A AD597AH TO-100 H-10A AD597AR* Plastic SOIC SO-8

*Consult factory for availability.

–2–

REV. B

Table I. Output Voltage vs. Thermocouple Temperature (Ambient +608C, VS = –5 V, +15 V)

Thermocouple Type J AD596 Type K AD597 Temperature Voltage Output Voltage Output 8C mVmVmVmV

–200 –7.890 –1370 –5.891 –1446 –180 –7.402 –1282 –5.550 –1362 –160 –6.821 –1177 –5.141 –1262 –140 –6.159 –1058 –4.669 –1146 –120 –5.426 –925 –4.138 –1016

–100 –4.632 –782 –3.553 –872

–80 –3.785 –629 –2.920 –717 –60 –2.892 –468 –2.243 –551 –40 –1.960 –299 –1.527 –375 –20 –.995 –125 –.777 –191

–10 –.501 –36 –.392 –96

005400 10 .507 146 .397 97 20 1.019 238 .798 196 25 1.277 285 1.000 245

30 1.536 332 1.203 295 40 2.058 426 1.611 395 50 2.585 521 2.022 496 60 3.115 617 2.436 598 80 4.186 810 3.266 802

100 5.268 1006 4.095 1005 120 6.359 1203 4.919 1207 140 7.457 1401 5.733 1407 160 8.560 1600 6.539 1605 180 9.667 1800 7.338 1801

200 10.777 2000 8.137 1997 220 11.887 2201 8.938 2194 240 12.998 2401 9.745 2392 260 14.108 2602 10.560 2592 280 15.217 2802 11.381 2794

300 16.325 3002 12.207 2996 320 17.432 3202 13.039 3201 340 18.537 3402 13.874 3406 360 19.640 3601 14.712 3611 380 20.743 3800 15.552 3817

400 21.846 3999 16.395 4024 420 22.949 4198 17.241 4232 440 24.054 4398 18.088 4440 460 25.161 4598 18.938 4649 480 26.272 4798 19.788 4857

AD596/AD597

Thermocouple Type J AD596 Type K AD597 Temperature Voltage Output Voltage Output 8CmVmVmVmV

500 27.388 5000 20.640 5066 520 28.511 5203 21.493 5276 540 29.642 5407 22.346 5485 560 30.782 5613 23.198 5694 580 31.933 5821 24.050 5903

600 33.096 6031 24.902 6112 620 34.273 6243 25.751 6321 640 35.464 6458 26.599 6529 660 36.671 6676 27.445 6737 680 37.893 6897 28.288 6944

700 39.130 7120 29.128 7150 720 40.382 7346 29.965 7355 740 41.647 7575 30.799 7560 750 42.283 7689 31.214 7662 760 – – 31.629 7764

780 – – 32.455 7966 800 – – 33.277 8168 820 – – 34.095 8369 840 – – 34.909 8569 860 – – 35.718 8767

880 – – 36.524 8965 900 – – 37.325 9162 920 – – 38.122 9357 940 – – 38.915 9552 960 – – 39.703 9745

980 – – 40.488 9938 1000 – – 41.269 10130 1020 – – 42.045 10320 1040 – – 42.817 10510 1060 – – 43.585 10698

1080 – – 44.439 10908 1100 – – 45.108 11072 1120 – – 45.863 11258 1140 – – 46.612 11441 1160 – – 47.356 11624

1180 – – 48.095 11805 1200 – – 48.828 11985 1220 – – 49.555 12164 1240 – – 50.276 12341 1250 – – 50.633 12428

REV. B –3–

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