FEATURES
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LTC2986/LTC2986-1
Multi-Sensor High
Accuracy Digital Temperature
Measurement System with EEPROM
DESCRIPTION
The
LTC 2986
measures a wide variety of temperature
sensors and digitally outputs the result, in °C or °F with
,
0.1°C accuracy and 0.001°C resolution. The LTC2986 can
measure the temperature of virtually all standard (Type B,
E, J, K, N, S, R, T) or custom thermocouples, automatically
compensate for cold junction temperatures and linearize
the results. The device can also measure temperature
with standard 2-, 3- or 4-wire RTDs, thermistors, and
diodes. The LTC2986 includes excitation current sources
and fault detection circuitry appropriate for each type of
temperature sensor.
®
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Directly Digitizes 2-, 3- or 4-Wire RTDs,
Thermocouples, Thermistors, and Diodes
On-Chip EEPROM (LTC2986-1) Stores Channel
Configuration Data and Custom Coefficients
Single 2.85V to 5.25V Supply
10 Flexible Inputs Allow Interchanging Sensors
Automatic Thermocouple Cold Junction Compensation
Built-In Standard and User-Programmable Coefficients
for Thermocouples, RTDs and Thermistors
Measures Negative Thermocouple Voltages
Automatic Burn Out, Short-Circuit and Fault Detection
Buffered Inputs Allow External Protection
Simultaneous 50Hz/60Hz Rejection
Includes 15ppm/°C (Max) Reference
Includes Special Protection Modes
Direct Thermocouple Measurements
Direct RTD Measurements
Direct Thermistor Measurements
Custom Sensor Applications
APPLICATIONS
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The LTC2986/LTC2986-1 are 10-channel software and pin-
compatible versions of the 20-channel LTC2983/LTC2984.
Additional features include special modes that enable easy
protection in universal multi-sensor applications, custom
tables for generic ADC readings, and direct temperature
readout from active analog temperature sensors. The
LTC2986-1 is the EEPROM version of the LTC2986.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Patents Pending
TYPICAL APPLICATION
Thermocouple Measurement with Automatic Cold Junction Compensation
2.85V TO 5.25V
1k
0.1µF
1k
24-BIT
∆∑ ADC
LTC2986-1
Typical Temperature Error
Contribution
0.5
0.4
0.3
0.2
ERROR (°C)
0.1
0
–0.1
–0.2
–0.3
–0.4
3904 DIODE
RTD
THERMISTOR
THERMOCOUPLE
R
SENSE
2k
24-BIT
∆∑ ADC
LINEARIZATION/
FAULT DETECTION
SPI
INTERFACE
°C/°F
4 3
PT-100
RTD
24-BIT
∆∑ ADC
V
REF
(15ppm/°C)
COM
29861 TA01a
–0.5
–200 0
200 400 600 800 1000 1200 1400
TEMPERATURE (°C)
29861 TA01b
2
1
EEPROM
29861fa
For more information
www.linear.com/LTC2986
1
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
LTC2986/LTC2986-1
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
GND
V
REF_BYP
NC
GND
V
DD
GND
V
DD
GND
V
DD
GND
V
DD
GND
13
14
15
16
17
18
19
20
21
22
23
24
12
11
10
9
8
7
6
5
4
3
2
1
LX PACKAGE
48-LEAD (7mm
×
7mm) PLASTIC LQFP
T
JMAX
= 150°C,
θ
JA
= 57°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC2986CLX#PBF
LTC2986ILX#PBF
LTC2986HLX#PBF
LTC2986CLX-1#PBF
LTC2986ILX-1#PBF
LTC2986HLX-1#PBF
TRAY
LTC2986CLX#PBF
LTC2986ILX#PBF
LTC2986HLX#PBF
LTC2986CLX-1#PBF
LTC2986ILX-1#PBF
LTC2986HLX-1#PBF
http://www.linear.com/product/LTC2986#orderinfo
PART MARKING*
LTC2986LX
LTC2986LX
LTC2986LX
LTC2986LX-1
LTC2986LX-1
LTC2986LX-1
PACKAGE DESCRIPTION
48-Lead (7mm
×
7mm) LQFP
48-Lead (7mm
×
7mm) LQFP
48-Lead (7mm
×
7mm) LQFP
48-Lead (7mm
×
7mm) LQFP
48-Lead (7mm
×
7mm) LQFP
48-Lead (7mm
×
7mm) LQFP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
CH10
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
COM
25
26
27
28
29
30
31
32
33
34
35
36
Supply Voltage (V
DD
) ................................... –0.3V to 6V
Analog Input Pins (CH1 to
CH10, COM) ................................. –0.3V to (V
DD
+ 0.3V)
Input Current (CH1 to CH10, COM) ...................... ±15mA
Digital Inputs (CS, SDI,
SCK,
RESET)
................................ –0.3V to (V
DD
+ 0.3V)
Digital Outputs (SDO, INTERRUPT) –0.3V to (V
DD
+ 0.3V)
V
REFP
........................................................ –0.3V to 2.8V
Q1, Q2, Q3, LDO, V
REFOUT,
V
REF_BYP
(Note 18)
Reference Short-Circuit Duration ..................... Indefinite
Operating Temperature Range
LTC2986C ................................................ 0°C to 70°C
LTC2986I .............................................–40°C to 85°C
LTC2986H .......................................... –40°C to 125°C
V
REFOUT
V
REFP
GND
CH1
CH2
CH3
CH4
CH5
CH6
CH7
CH8
CH9
48
47
46
45
44
43
42
41
40
39
38
37
Q1
Q2
Q3
V
DD
GND
LDO
RESET
CS
SDI
SDO
SCK
INTERRUPT
29861fa
For more information
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3
LTC2986/LTC2986-1
COMPLETE SYSTEM ELECTRICAL CHARACTERISTICS
PARAMETER
Supply Voltage
Supply Current
Sleep Current
Input Range
Output Rate
Output Rate
Input Common Mode Rejection
Input Normal Mode Rejection
Input Normal Mode Rejection
Input Normal Mode Rejection
Power-On Reset Threshold
Analog Power-Up
Digital Initialization
(Note 11)
(Note 12)
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which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
CONDITIONS
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The
l
denotes the specifications
TYP
15
25
MAX
5.25
20
60
V
DD
– 0.3
164
246
170
255
UNITS
V
mA
µA
V
ms
ms
dB
dB
dB
dB
2.25
100
100
V
ms
ms
MIN
2.85
All Analog Input Channels
Two Conversion Cycle Mode (Notes 6, 9)
Three Conversion Cycle Mode (Notes 6, 9)
50Hz/60Hz (Note 4)
60Hz (Notes 4, 7)
50Hz (Notes 4, 8)
50Hz/60Hz (Notes 4, 6, 9)
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–0.05
150
225
120
120
120
75
The
l
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C.
PARAMETER
Resolution (No Missing Codes)
Integral Nonlinearity
Offset Error
Offset Error Drift
Positive Full-Scale Error
Positive Full-Scale Drift
Input Leakage
Negative Full-Scale Error
Negative Full-Scale Drift
Input Referred Noise
Common Mode Input Range
RTD Excitation Current
RTD Excitation Current Matching
Thermistor Excitation Current
(Note 16)
Continuously Calibrated
(Note 16)
(Note 4)
(Notes 3, 15)
(Notes 3, 15)
(Note 19)
H-Grade
(Notes 3, 15)
(Notes 3, 15)
(Note 5)
H-Grade
CONDITIONS
–V
REFOUT/2
≤ V
IN
≤ +V
REFOUT/2
V
IN(CM)
= 1.25V (Note 15)
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ADC ELECTRICAL CHARACTERISTICS
MIN
24
TYP
2
0.5
10
0.1
MAX
30
2
20
100
0.5
1
10
100
UNITS
Bits
ppm of V
REF
µV
nV/°C
ppm of V
REF
ppm of V
REF
/°C
nA
nA
ppm of V
REF
ppm of V
REF
/°C
µV
RMS
µV
RMS
V
%
%
0.1
0.8
–0.05
–25
–37.5
Table 33
Table 57
0.5
1.5
2.0
V
DD
– 0.3
25
37.5
Error within Noise Level of ADC
29861fa
4
For more information
www.linear.com/LTC2986
LTC2986/LTC2986-1
REFERENCE ELECTRICAL CHARACTERISTICS
PARAMETER
Output Voltage
Output Voltage Temperature Coefficient
Output Voltage Temperature Coefficient
Line Regulation
Load Regulation
Output Voltage Noise
Output Short-Circuit Current
Turn-On Time
Long Term Drift of Output Voltage (Note 13)
Hysteresis (Note 14)
∆T = 0°C to 70°C
∆T = –40°C to 85°C
I
OUT(SOURCE)
= 100µA
I
OUT(SINK)
= 100µA
0.1Hz ≤ f ≤ 10Hz
10Hz ≤ f ≤ 1kHz
Short V
REFOUT
to GND
Short V
REFOUT
to V
DD
0.1% Setting, C
LOAD
= 1µF
CONDITIONS
V
REFOUT
(Note 10)
I-Grade, H-Grade
C-Grade
l
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l
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the full operating temperature range, otherwise specifications are at T
A
= 25°C.
The
l
denotes the specifications which apply over
MIN
2.49
3
3
TYP
MAX
2.51
15
20
10
5
5
4
4.5
40
30
115
60
30
70
UNITS
V
ppm/°C
ppm/°C
ppm/V
mV/mA
mV/mA
µV
P-P
µV
P-P
mA
mA
µs
ppm/√kHr
ppm
ppm
full operating temperature range, otherwise specifications are at T
A
= 25°C.
SYMBOL
PARAMETER
External SCK Frequency Range
External SCK LOW Period
External SCK HIGH Period
t
1
t
2
t
3
t
4
t
5
t
6
t
7
CS↓
to SDO Valid
CS↑
to SDO Hi-Z
CS↓
to SCK↑
SCK↓ to SDO Valid
SDO Hold After SCK↓
SDI Setup Before SCK↑
SDI HOLD After SCK↑
High Level Input Voltage
Low Level Input Voltage
Digital Input Current
Digital Input Capacitance
LOW Level Output Voltage (SDO, INTERRUPT)
High Level Output Voltage (SDO, INTERRUPT)
Hi-Z Output Leakage (SDO)
CS,
SDI, SCK,
RESET
CS,
SDI, SCK,
RESET
CS,
SDI, SCK,
RESET
CS,
SDI, SCK,
RESET
I
O
= –800µA
I
O
= 1.6mA
CONDITIONS
DIGITAL INPUTS AND DIGITAL OUTPUTS
The
l
denotes the specifications which apply over the
MIN
l
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l
l
l
l
l
l
l
l
TYP
MAX
2
UNITS
MHz
ns
ns
0
250
250
0
0
100
200
200
225
ns
ns
ns
ns
ns
ns
ns
V
10
100
100
V
DD
– 0.5
0.5
–10
10
10
0.4
V
DD
– 0.5
–10
10
V
µA
pF
V
V
µA
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29861fa
For more information
www.linear.com/LTC2986
5
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