LTC2984
Multi-Sensor High
Accuracy Digital Temperature
Measurement System with EEPROM
FEATURES DESCRIPTION
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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
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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,
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Single 2.85V to 5.25V Supply
E, J, K, N, S, R, T) or custom thermocouples, automatically
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20 Flexible Inputs Allow Interchanging Sensors
compensate for cold junction temperatures and linearize
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Automatic Thermocouple Cold Junction Compensation
the results. The device can also measure temperature with
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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-
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Measures Negative Thermocouple Voltages
sor connections and configuration options. The LTC2984
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Automatic Burn Out, Short-Circuit and Fault Detection
includes excitation current sources and fault detection
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Buffered Inputs Allow External Protection
circuitry appropriate for each type of temperature sensor
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Simultaneous 50Hz/60Hz Rejection
as well as an EEPROM for storing custom coefficients and
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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
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voltages, or external amplifiers. All signals are buffered and
Direct Thermocouple Measurements
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simultaneously digitized with three high accuracy, 24-bit
Direct RTD Measurements
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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
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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
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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
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For more information www.linear.com/LTC2984