Precision Thermocouple Amplifiers with Cold Junction Compensation Data Sheet AD8494/AD8495/AD8496/AD8497 FEATURES FUNCTIONAL BLOCK DIAGRAM REF Low cost and easy to use Pretrimmed for J or K type thermocouples AD8494/AD8495/ AD8496/AD8497 +IN Internal cold junction compensation ESD AND OVP A2 High impedance differential input Standalone 5 mV/C thermometer COLD JUNCTION Reference pin allows offset adjustment THERMO- A3 OUT COMPENSATION COUPLE Thermocouple break detection Laser wafer trimmed to 1C initial accuracy and A1 IN 0.025C/C ambient temperature rejection ESD AND OVP 1M Low power: <1 mW at V = 5 V S Wide power supply range SENSE Single supply: 2.7 V to 36 V Figure 1. Dual supply: 2.7 V to 18 V Small, 8-lead MSOP Table 1. Device Temperature Ranges Optimized Temperature Range Thermo- APPLICATIONS Couple Ambient Temperature Measurement J or K type thermocouple temperature measurement Part No. Type (Reference Junction) Junction Setpoint controller AD8494 J 0C to 50C Full J type range Celsius thermometer AD8495 K 0C to 50C Full K type range Universal cold junction compensator AD8496 J 25C to 100C Full J type range White goods (oven, stovetop) temperature measurements AD8497 K 25C to 100C Full K type range Exhaust gas temperature sensing Catalytic converter temperature sensing GENERAL DESCRIPTION The AD8494/AD8495/AD8496/AD8497 are precision The AD8494/AD8495/AD8496/AD8497 allow a wide variety of instrumentation amplifiers with thermocouple cold junction supply voltages. With a 5 V single supply, the 5 mV/C output compensators on an integrated circuit. They produce a high allows the devices to cover nearly 1000 degrees of a thermo- level (5 mV/C) output directly from a thermocouple signal by couples temperature range. combining an ice point reference with a precalibrated amplifier. The AD8494/AD8495/AD8496/AD8497 work with 3 V supplies, They can be used as standalone thermometers or as switched allowing them to interface directly to lower supply ADCs. They output setpoint controllers using a fixed or remote setpoint can also work with supplies as large as 36 V in industrial systems control. that require a wide common-mode input range. The AD8494/AD8495/AD8496/AD8497 can be powered from a PRODUCT HIGHLIGHTS single-ended supply (less than 3 V) and can measure temperatures 1. Complete, precision laser wafer trimmed thermocouple below 0C by offsetting the reference input. To minimize self- signal conditioning system in a single IC package. heating, an unloaded AD849x typically operates with a total 2. Flexible pinout provides for operation as a setpoint supply current of 180 A, but it is also capable of delivering in controller or as a standalone Celsius thermometer. excess of 5 mA to a load. 3. Rugged inputs withstand 4 kV ESD and provide over- The AD8494 and AD8496 are precalibrated by laser wafer voltage protection (OVP) up to VS 25 V. trimming to match the characteristics of J type (iron-constantan) 4. Differential inputs reject common-mode noise on the thermocouples the AD8495 and AD8497 are laser trimmed to thermocouple leads. match the characteristics of K type (chromel-alumel) thermo- 5. Reference pin voltage can be offset to measure 0C on couples. See Table 1 for the optimized ambient temperature single supplies. range of each part. 6. Available in a small, 8-lead MSOP that is fully RoHS compliant. Rev. D Document Feedback 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20102018 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 08529-001AD8494/AD8495/AD8496/AD8497 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Thermocouples ........................................................................... 11 Applications ....................................................................................... 1 Thermocouple Signal Conditioner .......................................... 11 Functional Block Diagram .............................................................. 1 AD8494/AD8495/AD8496/AD8497 Architecture .................. 11 General Description ......................................................................... 1 Maximum Error Calculation .................................................... 12 Product Highlights ........................................................................... 1 Recommendations for Best Circuit Performance .................. 13 Revision History ............................................................................... 2 Applications Information .............................................................. 14 Specif icat ions ..................................................................................... 3 Basic Connection ....................................................................... 14 Absolute Maximum Ratings ............................................................ 5 Ambient Temperature Sensor ................................................... 14 Thermal Resistance ...................................................................... 5 Setpoint Controller .................................................................... 15 ESD Caution .................................................................................. 5 Measuring Negative Temperatures .......................................... 15 Pin Configuration and Function Descriptions ............................. 6 Reference Pin Allows Offset Adjustment ................................ 15 Typical Performance Characteristics ............................................. 7 Outline Dimensions ....................................................................... 16 Theory of Operation ...................................................................... 11 Ordering Guide .......................................................................... 16 REVISION HISTORY 4/2018Rev. C to Rev. D Changes to Table 3 ............................................................................ 5 10/2010Rev. 0 to Rev. A Changes to Linearity Error of the Thermocouple Section ....... 12 6/2011Rev. B to Rev. C Changes to Ambient Temperature Sensor Section .................... 14 Changes to Ordering Guide .......................................................... 16 Changes to Figure 35 and Figure 36 ............................................. 15 4/2011Rev. A to Rev. B 7/2010Revision 0: Initial Version Changes to Figure 1 .......................................................................... 1 Changes to Figure 33 and Figure 34 ............................................. 14 Changes to Figure 35 and Figure 36 ............................................. 15 Changes to Ordering Guide .......................................................... 16 Rev. D Page 2 of 16