Y LINEAR TECHNOLOGY Micro power Thermonuclear Cold Junction Compensatory FEATURES DESCRIPTION = 80xA Supply Current "The LT1025 is a micro power thermonuclear cold junction m 4V 10 36V Operation compensatory for use with type and T thermos (.5°C Initial Accuracy (A Version) couples. It utilizes wafer level and post-package trimming s Compatible with Standard Thermoplastic to achieve 0.5°C initial accuracy.
LT1025 ABSOLUTE MAXIMUM PARTINGS Input Supply Voltage. .. Output Voltage (Forced). . Output Short Circuit Duration. Operating Temperature Range LT1025AC, LT1025C . LT1025AM, LT1025M Storage Temperature Range.
LT1025 e TYPICAL PERFORMANCE CHARACTERISTICS 10mV/°C Output Temperature 10mVi°C Output Temperature Error LT1025 Error LT10254 Supply Current DOES NOT INCLUDE 308 8 4 180 PULL-DOWN CURRENT . REQUIRED FOR TEMPERATURES 160 o & 8 s 0 GUARANTEED LIMITS® BELOW o4 L2 710254 140 125 120 Tw25°0 —55°c=T ¢ I DETONATE 100 128 JUNCTION TEMPERATURE {°C) AUCTION TEMPERATURE (°C} SUPPLY VOLTAGE (V} *ERROR CURVE FACTORS IN THE NON LINEARITY TERM BUILT % TO THE LT1025. SEE THEORY OF OPERATION IN APPLICATION GUIDE SECTION.
111025 used. This shifts the cold junction from the user termination to the end of the extender so that the LT1025 can be located remotely from the user termination as shown in Figure 2. Rieslings. AMPLIFIER P e e HOT” T TF J Unction protean, / EXTENDER Noway corp CONNECTOR JUNCTION Figure 2 The four thermonuclear outputs on the LT1025 are (B), 51.7aVIPC/ (K and T), and 6xV/°C (R and S). These particular coefficients are chosen to match the room temperature (25°C) slope of the thermoplastic.
11025 A —— T positioned isotherm ally, especially the LT1025 R~ and appropriate output pins, the amplifier input pins, and the gain setting resistor leads. An effect to watch for is amplifier offset voltage warm-up drift caused by mismatched thermonuclear materials in the wire-bandleader system of the IC package. This effect can be as high as tens of micro volts in TO-5 cans with ovary Reads.
LT1025 100mV/°C output, needs a closed loop gain of =2,500. An ordinary op amp with a minimum open loop of 50,000 would have an initial gain error of Although closed loop gain is commonly trimmed, temperature drift of open loop gain will have a very deleterious effect on output accuracy. Minimum suggested open loop gain for type E, J, K, and T thermoplastic is 260,000. This gain is adequate for type R and S if output scaling is less.
LT1025 APPLICATION CIRCUITS Type K Thermometer with Grounded Thermonuclear Eliminating Amplifier Feedback Resistors {Output Goes Negative with Increasing Temperature} 18y 3 R 255k Vin j e Our /G [ ATk 15V “Rbs ok IF OUTPUT MUST SINK CURRENT, Re. MUST BE DECREASED APPROPRIATELY. R4 IS NOT REQUIRED (DEN} FOR 111026 TEMPERATURES 20°C WHEN SOURCING CURRENT ONLY. THAR EQUIVALENT.
11025 Type S Thermonuclear Amplifier with Ultra-Low Offset and Drift o 1000 R3 FULL-SCALE 906k TRIM 1% Sous 10my G R7 750k 0.000mY {INPUT OF AMPLIFIER GROUNDED) TRIM P2 FOR Vpyyp = @7 =1000°C. UR FOR V)@ + INPUT OF AMPLIFIER = ¢ Shiv THIS AMPLIFIER HAS A DELIBERATE OFFSET TO ALLOW OUTPUT SLOPE T0 BE SET INDEPENDENTLY FROM A2 ARBITRARY HIGH TEMPERATURE CENTER POINT (1000°C).
