Name: AD594CD
SKU: AD594CD
Price: 45.28367 USD
Availability: InStock

FUNCTIONAL BLOCK DIAGRAM

14 13 12 11 10 9 8

OVERLOAD

DETECT

ICE

POINT

COMP.

–TC

+TC

1234567

AD594/AD595

+IN +C +T COM –T –C V–

–IN –ALM +ALM V+ COMP VO FB

Monolithic Thermocouple Amplifiers

with Cold Junction Compensation

AD594/AD595

FEATURES

Pretrimmed for Type J (AD594) or

Type K (AD595) Thermocouples

Can Be Used with Type T Thermocouple Inputs

Low Impedance Voltage Output: 10 mV/ⴗC

Built-In Ice Point Compensation

Wide Power Supply Range: +5 V to ⴞ15 V

Low Power: <1 mW typical

Thermocouple Failure Alarm

Laser Wafer Trimmed to 1ⴗC Calibration Accuracy

Setpoint Mode Operation

Self-Contained Celsius Thermometer Operation

High Impedance Differential Input

Side-Brazed DIP or Low Cost Cerdip

PRODUCT DESCRIPTION

The AD594/AD595 is a complete instrumentation amplifier and

thermocouple cold junction compensator on a monolithic chip.

It combines an ice point reference with a precalibrated amplifier

to produce a high level (10 mV/°C) output directly from a ther-

mocouple signal. Pin-strapping options allow it to be used as a

linear amplifier-compensator or as a switched output setpoint

controller using either fixed or remote setpoint control. It can

be used to amplify its compensation voltage directly, thereby

converting it to a stand-alone Celsius transducer with a low

impedance voltage output.

The AD594/AD595 includes a thermocouple failure alarm that

indicates if one or both thermocouple leads become open. The

alarm output has a flexible format which includes TTL drive

capability.

The AD594/AD595 can be powered from a single ended supply

(including +5 V) and by including a negative supply, tempera-

tures below 0°C can be measured. To minimize self-heating, an

unloaded AD594/AD595 will typically operate with a total sup-

ply current 160 µA, but is also capable of delivering in excess of

±5 mA to a load.

The AD594 is precalibrated by laser wafer trimming to match

the characteristic of type J (iron-constantan) thermocouples and

the AD595 is laser trimmed for type K (chromel-alumel) inputs.

The temperature transducer voltages and gain control resistors

are available at the package pins so that the circuit can be

recalibrated for the thermocouple types by the addition of two

or three resistors. These terminals also allow more precise cali-

bration for both thermocouple and thermometer applications.

The AD594/AD595 is available in two performance grades. The

C and the A versions have calibration accuracies of ±1°C and

±3°C, respectively. Both are designed to be used from 0°C to

+50°C, and are available in 14-pin, hermetically sealed, side-

brazed ceramic DIPs as well as low cost cerdip packages.

PRODUCT HIGHLIGHTS

1. The AD594/AD595 provides cold junction compensation,

amplification, and an output buffer in a single IC package.

2. Compensation, zero, and scale factor are all precalibrated by

laser wafer trimming (LWT) of each IC chip.

3. Flexible pinout provides for operation as a setpoint control-

ler or a stand-alone temperature transducer calibrated in

degrees Celsius.

4. Operation at remote application sites is facilitated by low

quiescent current and a wide supply voltage range +5 V to

dual supplies spanning 30 V.

5. Differential input rejects common-mode noise voltage on the

thermocouple leads.

REV. C

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., 1999

AD594/AD595–SPECIFICATIONS

REV. C

–2–

Model AD594A AD594C AD595A AD595C

Min Typ Max Min Typ Max Min Typ Max Min Typ Max Units

ABSOLUTE MAXIMUM RATING

to –V

36 36 36 36 Volts

Common-Mode Input Voltage –V

– 0.15 +V

–V

– 0.15 +V

–V

– 0.15 +V

–V

– 0.15 +V

Volts

Differential Input Voltage –V

–V

Volts

Alarm Voltages

+ALM –V

–V

+ 36 –V

–V

+ 36 –V

–V

+ 36 –V

–V

+ 36 Volts

–ALM –V

–V

Volts

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

Output Short Circuit to Common Indefinite Indefinite Indefinite Indefinite

TEMPERATURE MEASUREMENT

(Specified Temperature Range

0°C to +50°C)

Calibration Error at +25°C

ⴞ3 ⴞ1 ⴞ3 ⴞ1 °C

Stability vs. Temperature

ⴞ0.05 ⴞ0.025 ⴞ0.05 ⴞ0.025 °C/°C

Gain Error ⴞ1.5 ⴞ0.75 ⴞ1.5 ⴞ0.75 %

Nominal Transfer Function 10 10 10 10 mV/°C

AMPLIFIER CHARACTERISTICS

Closed Loop Gain

193.4 193.4 247.3 247.3

Input Offset Voltage (Temperature in °C) × (Temperature in °C) × (Temperature in °C) × (Temperature in °C) ×

51.70 µV/°C 51.70 µV/°C 40.44 µV/°C 40.44 µV/°C µV

Input Bias Current 0.1 0.1 0.1 0.1 µA

Differential Input Range –10 +50 –10 +50 –10 +50 mV

Common-Mode Range –V

– 0.15 –V

– 4 –V

– 0.15 –V

– 4 –V

– 0.15 –V

– 4 –V

– 0.15 –V

– 4 Volts

Common-Mode Sensitivity – RTO 10 10 10 10 mV/V

Power Supply Sensitivity – RTO 10 10 10 10 mV/V

Output Voltage Range

Dual Supply –V

+ 2.5 +V

– 2 –V

+ 2.5 +V

– 2 –V

+ 2.5 +V

– 2 –V

+ 2.5 +V

– 2 Volts

Single Supply 0 +V

– 2 0 –V

– 2 0 +V

+ 2 0 +V

– 2 Volts

Usable Output Current

±5 ±5 ±5 ± 5mA

3 dB Bandwidth 15 15 15 15 kHz

ALARM CHARACTERISTICS

CE(SAT)

at 2 mA 0.3 0.3 0.3 0.3 Volts

Leakage Current ⴞ1 ⴞ1 ⴞ1 ⴞ1 µA max

Operating Voltage at – ALM +V

– 4 +V

– 4 Volts

Short Circuit Current 20 20 20 20 mA

POWER REQUIREMENTS

Specified Performance +V

= 5, –V

= 0 +V

= 5, –V

= 0 +V

= 5, –V

= 0 +V

= 5, –V

= 0 Volts

Operating

to –V

≤ 30 +V

to –V

≤ 30 +V

to –V

≤ 30 +V

to –V

≤ 30 Volts

Quiescent Current (No Load)

160 300 160 300 160 300 160 300 µA

–V

100 100 100 100 µA

PACKAGE OPTION

TO-116 (D-14) AD594AD AD594CD AD595AD AD595CD

Cerdip (Q-14) AD594AQ AD594CQ AD595AQ AD595CQ

NOTES

Calibrated for minimum error at +25°C using a thermocouple sensitivity of 51.7 µV/°C. Since a J type thermocouple deviates from this straight line approximation, the AD594 will normally

read 3.1 mV when the measuring junction is at 0°C. The AD595 will similarly read 2.7 mV at 0°C.

Defined as the slope of the line connecting the AD594/AD595 errors measured at 0°C and 50°C ambient temperature.

Pin 8 shorted to Pin 9.

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.

–V

must not exceed –16.5 V.

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.

Specifications subject to change without notic

(@ +25ⴗC and V

= 5 V, Type J (AD594), Type K (AD595) Thermocouple,

unless otherwise noted)

INTERPRETING AD594/AD595 OUTPUT VOLTAGES

To achieve a temperature proportional output of 10 mV/°C and

accurately compensate for the reference junction over the rated

operating range of the circuit, the AD594/AD595 is gain trimmed

to match the transfer characteristic of J and K type thermocouples

at 25°C. For a type J output in this temperature range the TC is

51.70 µV/°C, while for a type K it is 40.44 µV/°C. The resulting

gain for the AD594 is 193.4 (10 mV/°C divided by 51.7 µV/°C)

and for the AD595 is 247.3 (10 mV/°C divided by 40.44 µV/°C).

In addition, an absolute accuracy trim induces an input offset to

the output amplifier characteristic of 16 µV for the AD594 and

11 µV for the AD595. This offset arises because the AD594/

AD595 is trimmed for a 250 mV output while applying a 25°C

thermocouple input.

Because a thermocouple output voltage is nonlinear with respect

to temperature, and the AD594/AD595 linearly amplifies the

compensated signal, the following transfer functions should be

used to determine the actual output voltages:

AD594 output = (Type J Voltage + 16 µV) × 193.4

AD595 output = (Type K Voltage + 11 µV) × 247.3 or conversely:

Type J voltage = (AD594 output/193.4) – 16 µV

Type K voltage = (AD595 output/247.3) – 11 µV

Table I lists the ideal AD594/AD595 output voltages as a func-

tion of Celsius temperature for type J and K ANSI standard

thermocouples, with the package and reference junction at

25°C. As is normally the case, these outputs are subject to cali-

bration, gain and temperature sensitivity errors. Output values

for intermediate temperatures can be interpolated, or calculated

using the output equations and ANSI thermocouple voltage

tables referred to zero degrees Celsius. Due to a slight variation

in alloy content between ANSI type J and DIN F

-C

AD594/AD595

REV. C

–3–

Thermocouple Type J AD594 Type K AD595

Temperature Voltage Output Voltage Output

°C mVmVmVmV

–200 –7.890 –1523 –5.891 –1454

–180 –7.402 –1428 –5.550 –1370

–160 –6.821 –1316 –5.141 –1269

–140 –6.159 –1188 –4.669 –1152

–120 –5.426 –1046 –4.138 –1021

–100 –4.632 –893 –3.553 –876

–80 –3.785 –729 –2.920 –719

–60 –2.892 –556 –2.243 –552

–40 –1.960 –376 –1.527 –375

–20 –.995 –189 –.777 –189

–10 –.501 –94 –.392 –94

0 0 3.1 0 2.7

10 .507 101 .397 101

20 1.019 200 .798 200

25 1.277 250 1.000 250

30 1.536 300 1.203 300

40 2.058 401 1.611 401

50 2.585 503 2.022 503

60 3.115 606 2.436 605

80 4.186 813 3.266 810

100 5.268 1022 4.095 1015

120 6.359 1233 4.919 1219

140 7.457 1445 5.733 1420

160 8.560 1659 6.539 1620

180 9.667 1873 7.338 1817

200 10.777 2087 8.137 2015

220 11.887 2302 8.938 2213

240 12.998 2517 9.745 2413

260 14.108 2732 10.560 2614

280 15.217 2946 11.381 2817

300 16.325 3160 12.207 3022

320 17.432 3374 13.039 3227

340 18.537 3588 13.874 3434

360 19.640 3801 14.712 3641

380 20.743 4015 15.552 3849

400 21.846 4228 16.395 4057

420 22.949 4441 17.241 4266

440 24.054 4655 18.088 4476

460 25.161 4869 18.938 4686

480 26.272 5084 19.788 4896

Thermocouple Type J AD594 Type K AD595

Temperature Voltage Output Voltage Output

°CmVmVmVmV

500 27.388 5300 20.640 5107

520 28.511 5517 21.493 5318

540 29.642 5736 22.346 5529

560 30.782 5956 23.198 5740

580 31.933 6179 24.050 5950

600 33.096 6404 24.902 6161

620 34.273 6632 25.751 6371

640 35.464 6862 26.599 6581

660 36.671 7095 27.445 6790

680 37.893 7332 28.288 6998

700 39.130 7571 29.128 7206

720 40.382 7813 29.965 7413

740 41.647 8058 30.799 7619

750 42.283 8181 31.214 7722

760 – – 31.629 7825

780 – – 32.455 8029

800 – – 33.277 8232

820 – – 34.095 8434

840 – – 34.909 8636

860 – – 35.718 8836

880 – – 36.524 9035

900 – – 37.325 9233

920 – – 38.122 9430

940 – – 38.915 9626

960 – – 39.703 9821

980 – – 40.488 10015

1000 – – 41.269 10209

1020 – – 42.045 10400

1040 – – 42.817 10591

1060 – – 43.585 10781

1080 – – 44.439 10970

1100 – – 45.108 11158

1120 – – 45.863 11345

1140 – – 46.612 11530

1160 – – 47.356 11714

1180 – – 48.095 11897

1200 – – 48.828 12078

1220 – – 49.555 12258

1240 – – 50.276 12436

1250 – – 50.633 12524

Table I. Output Voltage vs. Thermocouple Temperature (Ambient +25°C, V

= –5 V, +15 V)

thermocouples Table I should not be used in conjunction with

European standard thermocouples. Instead the transfer function

given previously and a DIN thermocouple table should be used.

ANSI type K and DIN N

-N

thermocouples are composed

OVERLOAD

DETECT

–TC

+TC

1234567

13 12 11 10

AD594/

AD595

CONSTANTAN

(ALUMEL)

IRON

(CHROMEL)

+5V

COMMON

ICE

POINT

COMP.

10mV/8C

Figure 1. Basic Connection, Single Supply Operation

of identical alloys and exhibit similar behavior. The upper tem-

perature limits in Table I are those recommended for type J and

type K thermocouples by the majority of vendors.

SINGLE AND DUAL SUPPLY CONNECTIONS

The AD594/AD595 is a completely self-contained thermocouple

conditioner. Using a single +5 V supply the interconnections

shown in Figure 1 will provide a direct output from a type J

thermocouple (AD594) or type K thermocouple (AD595) mea-

suring from 0°C to +300°C.

Any convenient supply voltage from +5 V to +30 V may be

used, with self-heating errors being minimized at lower supply

levels. In the single supply configuration the +5 V supply con-

nects to Pin 11 with the V– connection at Pin 7 strapped to

power and signal common at Pin 4. The thermocouple wire in-

puts connect to Pins 1 and 14 either directly from the measuring

point or through intervening connections of similar thermo-

couple wire type. When the alarm output at Pin 13 is not used it

should be connected to common or –V. The precalibrated feed-

back network at Pin 8 is tied to the output at Pin 9 to provide a

10 mV/°C nominal temperature transfer characteristic.

By using a wider ranging dual supply, as shown in Figure 2, the

AD594/AD595 can be interfaced to thermocouples measuring

both negative and extended positive temperatures.

Part #	AD594CD
Description	Temp Sensor Analog 14-Pin TO-116 Tube
Category	IC
Availability	In Stock
Qty	50

Qty	Price
1 - 3	$45.28367
4 - 8	$36.02110
9 - 16	$33.96275
17 - 24	$31.56135
25 +	$28.13076

AD594CD

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