LTC2984 Multi-Sensor High Accuracy Digital Temperature Measurement System with EEPROM FEATURES DESCRIPTION n Directly Digitizes 2-, 3-, or 4-Wire RTDs, The LTC 2984 measures a wide variety of temperature Thermocouples, Thermistors, and Diodes sensors and digitally outputs the result, in C or F, with n On-Chip EEPROM Stores Channel Configuration Data 0.1C accuracy and 0.001C resolution. The LTC2984 can and Custom Coefficients measure the temperature of virtually all standard (type B, n Single 2.85V to 5.25V Supply E, J, K, N, S, R, T) or custom thermocouples, automatically n 20 Flexible Inputs Allow Interchanging Sensors compensate for cold junction temperatures and linearize n Automatic Thermocouple Cold Junction Compensation the results. The device can also measure temperature with n Built-In Standard and User-Programmable Coefficients standard 2-, 3-, or 4-wire RTDs, thermistors, and diodes. for Thermocouples, RTDs and Thermistors It has 20 reconfigurable analog inputs enabling many sen- n Measures Negative Thermocouple Voltages sor connections and configuration options. The LTC2984 n Automatic Burn Out, Short-Circuit and Fault Detection includes excitation current sources and fault detection n Buffered Inputs Allow External Protection circuitry appropriate for each type of temperature sensor n Simultaneous 50Hz/60Hz Rejection as well as an EEPROM for storing custom coefficients and n Includes 15ppm/C (Max) Reference (I-Grade) channel configuration data. The LTC2984 allows direct interfacing to ground referenced APPLICATIONS sensors without the need for level shifters, negative supply n voltages, or external amplifiers. All signals are buffered and Direct Thermocouple Measurements n simultaneously digitized with three high accuracy, 24-bit Direct RTD Measurements n ADC s, driven by an internal 10ppm/C (maximum) reference. Direct Thermistor Measurements L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear n Custom Sensor Applications Technology Corporation. All other trademarks are the property of their respective owners. Patents Pending TYPICAL APPLICATION Thermocouple Measurement with Automatic Cold Junction Compensation Typical Temperature Error Contribution 2.85V TO 5.25V 0.5 1k LTC2984 0.4 0.1F 24-BIT 0.3 1k THERMISTOR ADC 0.2 THERMOCOUPLE 0.1 0 LINEARIZATION/ SPI 0.1 FAULT DETECTION INTERFACE R SENSE 3904 DIODE 24-BIT 0.2 2k C/F ADC RTD 0.3 0.4 4 3 0.5 200 200 400 600 800 1000 1200 1400 0 PT-100 TEMPERATURE (C) 24-BIT RTD ADC 2 2984 TA01b 1 V (10ppm/C) REF EEPROM 2984 TA01a 2984fb 1 For more information www.linear.com/LTC2984 ERROR (C)LTC2984 TABLE OF CONTENTS Features ............................................................................................................................ 1 Applications ....................................................................................................................... 1 Typical Application ............................................................................................................... 1 Description......................................................................................................................... 1 Absolute Maximum Ratings ..................................................................................................... 3 Order Information ................................................................................................................. 3 Pin Configuration ................................................................................................................. 3 Complete System Electrical Characteristics .................................................................................. 4 ADC Electrical Characteristics .................................................................................................. 4 Reference Electrical Characteristics ........................................................................................... 5 Digital Inputs and Digital Outputs .............................................................................................. 5 EEPROM Characteristics ......................................................................................................... 6 Typical Performance Characteristics .......................................................................................... 7 Pin Functions .....................................................................................................................10 Block Diagram ....................................................................................................................11 Test Circuits ......................................................................................................................12 Timing Diagram ..................................................................................................................12 Overview ..........................................................................................................................13 Applications Information .......................................................................................................17 EEPROM Overview................................................................................................................................................ 23 EEPROM Read/Write Validation ............................................................................................................................ 23 EEPROM Write Operation ..................................................................................................................................... 23 EEPROM Read Operation ...................................................................................................................................... 24 Thermocouple Measurements .............................................................................................................................. 25 Diode Measurements ............................................................................................................................................ 28 RTD Measurements .............................................................................................................................................. 32 Thermistor Measurements .................................................................................................................................... 50 Supplemental Information ......................................................................................................61 Direct ADC Measurements .................................................................................................................................... 61 Fault Protection and Anti-Aliasing ......................................................................................................................... 63 2- and 3-Cycle Conversion Modes ........................................................................................................................ 63 Running Conversions Consecutively on Multiple Channels ................................................................................... 64 Entering/Exiting Sleep Mode ................................................................................................................................. 64 MUX Configuration Delay ...................................................................................................................................... 64 Global Configuration Register ............................................................................................................................... 65 Reference Considerations ..................................................................................................................................... 65 Custom Thermocouples .........................................................................................................65 Custom RTDs .....................................................................................................................68 Custom Thermistors .............................................................................................................71 Package Description ............................................................................................................76 Revision History .................................................................................................................77 Typical Application ..............................................................................................................78 Related Parts .....................................................................................................................78 2984fb 2 For more information www.linear.com/LTC2984