LT1025 Micropower Thermocouple Cold Junction Compensator FEATURES DESCRIPTIO n 80m A Supply Current The LT 1025 is a micropower thermocouple cold junction n 4V to 36V Operation compensator for use with type E, J, K, R, S, and T n 0.5 C Initial Accuracy (A Version) thermocouples. It utilizes wafer level and post-package n Compatible with Standard Thermocouples trimming to achieve 0.5 C initial accuracy. Special curvature (E, J, K, R, S, T) correction circuitry is used to match the bow found in all n Auxiliary 10mV/ C Output thermocouples so that accurate cold junction compensation n Available in 8-Lead PDIP and SO Packages is maintained over a wider temperature range. The LT1025 will operate with a supply voltage from 4V to 36V. U Typical supply current is 80m A, resulting in less than 0.1 C APPLICATIO S internal temperature rise for supply voltages under 10V. n Thermocouple Cold Junction Compensator A 10mV/ C output is available at low impedance, in addition n Centigrade Thermometer to the direct thermocouple voltages of 60.9m V/ C (E), n Temperature Compensation Network 51.7m V/ C (J), 40.3m V/ C (K, T) and 5.95m V/ C (R, S). All outputs are essentially independent of power supply voltage. A special kit is available (LTK001) which contains an LT1025 and a custom tailored thermocouple amplifier. The amplifier and compensator are matched to allow a much tighter specifi- cation of temperature error than would be obtained by adding the compensator and amplifier errors on a worst-case basis. The amplifier from this kit is available separately as LTKA0x. The LT1025 is available in either an 8-pin PDIP or 8-pin SO package for temperatures between 0 C and 70 C. , LTC and LT are registered trademarks of Linear Technology Corporation. BLOCK DIAGRA TYPICAL APPLICATIO Type K 10mV/ C Thermometer E 60.9V/C R2 R3** 100 255k V IN J 51.7V/C FULL-SCALE TRIM 1% + R1 BUFFER K,T 40.6V/C BOW* + 1k V CORRECTION + 1% C2 V VOLTAGE 0.1F R, S 6V/C V OUT LTKA0x 10mV/C V 10mV/C IN K + + TEMPERATURE V R COMMON *R4 , R4 IS NOT REQUIRED SENSOR LT1025 30A V (OPEN) FOR LT1025 TEMPERATURES 0C TYPE K V 10mV/C V 0 O C1 GND R **SELECTED FOR 0C TO 100C RANGE 0.1F R4* GND *CORRECTS FOR BOW OR EQUIVALENT. SEE IN COLD JUNCTION, NOT AMPLIFIER CONSIDERATIONS IN PROBE (HOT JUNCTION) LT1025 BD01 V LT1025 TA01 1025fb 1 U W ULT1025 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW ORDER PART Input Supply Voltage .......................................... 36V E J 1 NUMBER 8 60.9V/C 51.7V/C Output Voltage (Forced)........................................ 5V K, T V 2 7 IN 40.6V/C Output Short-Circuit Duration ..................... Indefinite LT1025ACN8 V R, S O 3 6 Operating Temperature Range 10mV/C 6V/C LT1025CN8 R 4 5 GND COMMON LT1025AC, LT1025C ............................0 C to 70 C LT1025CS8 N8 PACKAGE S8 PACKAGE LT1025AM, LT1025M .................. 55 C to 125 C 8-LEAD PDIP 8-LEAD PLASTIC SO S8 PART MARKING Storage Temperature Range ............ 55 C to 150 C T = 150 C, q = 130 C/W (N8) JMAX JA 1025 T = 150 C, q = 190 C/W (S8) JMAX JA J8 PACKAGE 8-LEAD CERDIP LT1025AMJ8 T = 150 C, q = 100 C/W JMAX JA LT1025MJ8 OBSOLETE PACKAGE Consider the N8 Package for Alternate Source Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specificatons are at T = 25 C. V = 5V, Pin 5 tied to Pin 4, unless otherwise noted. A S PARAMETER CONDITIONS MIN TYP MAX UNITS Temperature Error at T = 25 C J 10mV/ C Output (Notes 4, 5) LT1025A 0.3 0.5 C LT1025 0.5 2.0 C Full Temperature Span l See Curve Resistor Divider Accuracy V = 10mV/ C OUT (Notes 2, 4) LT1025A E 60.6 60.9 61.3 m V/ C J 51.4 51.7 52.1 m V/ C K, T 40.3 40.6 41.0 m V/ C R, S 5.8 5.95 6.2 m V/ C LT1025 E 60.4 60.9 61.6 m V/ C J 51.2 51.7 52.3 m V/ C K, T 40.2 40.6 41.2 m V/ C R, S 5.75 5.95 6.3 m V/ C Supply Current 4V V 36V 50 80 100 m A IN LT1025AC, LT1025C l 50 150 m A LT1025AM, LT1025M l 200 m A Line Regulation (Note 3) 4V V 36V l 0.003 0.02 C/V IN Load Regulation (Note 3) 0 I 1mA l 0.04 0.2 C O Divider Impedance E 2.5 kW J 2.1 kW K, T 4.4 kW R, S 3.8 kW Change in Supply Current 4V V 36V 0.01 0.05 m A/V IN Note 1: Absolute Maximum Ratings are those values beyond which the Note 4: To calculate total temperature error at individual thermocouple life of a device may be impaired. outputs, add 10mV/ C output error to the resistor divider error. Total error for type K output at 25 C with an LT1025A is 0.5 C plus (0.4m V/ C)(25 C)/ Note 2: Divider accuracy is measured by applying a 10.000V signal to the (40.6m V/ C) = 0.5 C + 0.25 C = 0.75 C. output divider and measuring the individual outputs. Note 5: Temperature error is defined as the deviation from the following Note 3: Regulation does not include the effects of self-heating. See -4 2 formula: V = 10mV(T) + (10mV)(5.5 10 )(T 25 C) . The second Internal Temperature Rise in Application Guide. Load regulation is OUT term is a built-in nonlinearity designed to help compensate the nonlinearity 30m A I 1mA for T 0 C. O A of the cold junction. This bow is 0.34 C for a 25 C temperature change. 1025fb 2 U WWW