LTC2986/LTC2986-1
Multi-Sensor High
Accuracy Digital Temperature
Measurement System with EEPROM
FEATURES DESCRIPTION
n
Directly Digitizes 2-, 3- or 4-Wire RTDs, The LTC 2986 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 (LTC2986-1) Stores Channel 0.1C accuracy and 0.001C resolution. The LTC2986 can
ConfigurationData 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
10 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
n
Built-In Standard and User-Programmable Coefficients with standard 2-, 3- or 4-wire RTDs, thermistors, and
for Thermocouples, RTDs and Thermistors diodes. The LTC2986 includes excitation current sources
n
Measures Negative Thermocouple Voltages and fault detection circuitry appropriate for each type of
n
Automatic Burn Out, Short-Circuit and Fault Detection temperature sensor.
n
Buffered Inputs Allow External Protection
The LTC2986/LTC2986-1 are 10-channel software and pin-
n
Simultaneous 50Hz/60Hz Rejection
compatible versions of the 20-channel LTC2983/LTC2984.
n
Includes 15ppm/C (Max) Reference
Additional features include special modes that enable easy
n
Includes Special Protection Modes
protection in universal multi-sensor applications, custom
tables for generic ADC readings, and direct temperature
APPLICATIONS
readout from active analog temperature sensors. The
n
Direct Thermocouple Measurements
LTC2986-1 is the EEPROM version of the LTC2986.
n
Direct RTD Measurements
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
n
Direct Thermistor Measurements Technology Corporation. All other trademarks are the property of their respective owners.
Patents Pending
n
Custom Sensor Applications
TYPICAL APPLICATION
Thermocouple Measurement with Automatic Cold Junction Compensation Typical Temperature Error
Contribution
2.85V TO 5.25V
0.5
1k
LTC2986-1 0.4
0.1F
0.3
THERMISTOR
24-BIT
1k ADC 0.2 THERMOCOUPLE
0.1
0
SPI 0.1
LINEARIZATION/
INTERFACE
FAULT DETECTION
R
SENSE 0.2 3904 DIODE
24-BIT
2k C/F
RTD
ADC
0.3
0.4
4
3
0.5
200 0 200 400 600 800 1000 1200 1400
PT-100
TEMPERATURE (C)
24-BIT
RTD
ADC
2
29861 TA01b
1
V (15ppm/C)
EEPROM
REF
COM
29861 TA01a
29861fa
1
For more information www.linear.com/LTC2986
ERROR (C)LTC2986/LTC2986-1
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
LTC2986-1 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 (LTC2986-1) .......................................................................................................................... 23
EEPROM Read/Write Validation ............................................................................................................................ 23
EEPROM Write Operation ..................................................................................................................................... 23
EEPROM Read Operation (LTC2986-1) ................................................................................................................. 24
Thermocouple Measurements .............................................................................................................................. 25
Diode Measurements ............................................................................................................................................ 28
RTD Measurements .............................................................................................................................................. 32
Thermistor Measurements .................................................................................................................................... 51
Global Configuration Register ............................................................................................................................... 60
Input Overvoltage Protection Overview.............................................................................................................. 60
Active Analog Temperature Sensors ..................................................................................................................... 66
Direct ADC Measurements .................................................................................................................................... 70
2- and 3-Cycle Conversion Modes ........................................................................................................................ 75
Running Conversions Consecutively on Multiple Channels ................................................................................... 75
Entering/Exiting Sleep Mode ................................................................................................................................. 76
MUX Configuration Delay ...................................................................................................................................... 76
Reference Considerations ..................................................................................................................................... 76
Custom Thermocouples .........................................................................................................77
Custom RTDs .....................................................................................................................80
Custom Thermistors .............................................................................................................83
Package Description ............................................................................................................88
Revision History .................................................................................................................89
Typical Application ..............................................................................................................90
Related Parts .....................................................................................................................90
29861fa
2
For more information www.linear.com/LTC2986