FEATURES
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LTC2983
Multi-Sensor High Accuracy
Digital Temperature
Measurement System
DESCRIPTION
The
LTC
®
2983
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 LTC2983 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. It
has 20 reconfigurable analog inputs enabling many sen-
sor connections and configuration options. The LTC2983
includes excitation current sources and fault detection
circuitry appropriate for each type of temperature sensor.
The LTC2983 allows direct interfacing to ground referenced
sensors without the need for level shifters, negative supply
voltages, or external amplifiers. All signals are buffered and
simultaneously digitized with three high accuracy, 24-bit ∆∑
ADCs, driven by an internal 15ppm/°C (maximum) reference.
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
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Directly Digitize RTDs, Thermocouples, Thermistors
and Diodes
Single 2.85V to 5.25V Supply
Results Reported in °C or °F
20 Flexible Inputs Allow Interchanging Sensors
Automatic Thermocouple Cold Junction Compensation
Built-In Standard and User-Programmable Coefficients
for Thermocouples, RTDs and Thermistors
Configurable 2-, 3- or 4-Wire RTD Configurations
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 (I-Grade)
Direct Thermocouple Measurements
Direct RTD Measurements
Direct Thermistor Measurements
Custom Sensor Applications
APPLICATIONS
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TYPICAL APPLICATION
Thermocouple Measurement with Automatic Cold Junction Compensation
2.85V TO 5.25V
1k
0.1µF
1k
24-BIT
∆∑ ADC
LTC2983
Typical Temperature Error Contribution
0.5
0.4
0.3
0.2
ERROR (°C)
0.1
0
–0.1
–0.2
°C/°F
THERMISTOR
THERMOCOUPLE
R
SENSE
2k
LINEARIZATION/
FAULT DETECTION
24-BIT
∆∑ ADC
SPI
INTERFACE
3904 DIODE
–0.3
–0.4
–0.5
–200 0
RTD
4 3
PT-100
RTD
24-BIT
∆∑ ADC
V
REF
(10ppm/°C)
2983 TA01a
200 400 600 800 1000 1200 1400
TEMPERATURE (°C)
2983 TA01b
2
1
2983fc
For more information
www.linear.com/LTC2983
1
LTC2983
TABLE OF CONTENTS
Features ............................................................................................................................ 1
Applications ....................................................................................................................... 1
Typical Application ............................................................................................................... 1
Description......................................................................................................................... 1
Absolute Maximum Ratings ..................................................................................................... 3
Order Information ................................................................................................................. 3
Complete System Electrical Characteristics .................................................................................. 3
Pin Configuration ................................................................................................................. 3
ADC Electrical Characteristics .................................................................................................. 4
Reference Electrical Characteristics ........................................................................................... 4
Digital Inputs and Digital Outputs .............................................................................................. 5
Typical Performance Characteristics .......................................................................................... 6
Pin Functions ...................................................................................................................... 9
Block Diagram....................................................................................................................10
Test Circuits ......................................................................................................................11
Timing Diagram ..................................................................................................................11
Overview ..........................................................................................................................12
Applications Information .......................................................................................................16
Thermocouple Measurements .............................................................................................................................. 21
Diode Measurements ............................................................................................................................................ 24
RTD Measurements .............................................................................................................................................. 28
Thermistor Measurements .................................................................................................................................... 43
Direct ADC Measurements .................................................................................................................................... 55
Supplemental Information......................................................................................................55
Fault Protection and Anti-Aliasing ......................................................................................................................... 57
2- and 3-Cycle Conversion Modes ........................................................................................................................ 57
Running Conversions Consecutively on Multiple Channels................................................................................... 58
MUX Configuration Delay...................................................................................................................................... 58
Global Configuration Register ............................................................................................................................... 59
Custom Thermocouples .........................................................................................................59
Custom RTDs .....................................................................................................................62
Custom Thermistors .............................................................................................................65
Package Description ............................................................................................................70
Revision History .................................................................................................................71
Typical Application ..............................................................................................................72
Related Parts .....................................................................................................................72
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For more information
www.linear.com/LTC2983
LTC2983
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
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LX PACKAGE
48-LEAD (7mm
×
7mm) PLASTIC LQFP
ORDER INFORMATION
LEAD FREE FINISH
LTC2983CLX#PBF
LTC2983ILX#PBF
LTC2983HLX#PBF
TRAY
LTC2983CLX#PBF
LTC2983ILX#PBF
LTC2983HLX#PBF
PART MARKING*
LTC2983LX
LTC2983LX
LTC2983LX
PACKAGE DESCRIPTION
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
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/
which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
PARAMETER
Supply Voltage
Supply Current
Sleep Current
Input Range
Output Rate
Output Rate
Input Common Mode Rejection
Input Normal Mode Rejection
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)
CONDITIONS
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COMPLETE SYSTEM ELECTRICAL CHARACTERISTICS
MIN
2.85
CH10
CH11
CH12
CH13
CH14
CH15
CH16
CH17
CH18
CH19
CH20
COM
Supply Voltage (V
DD
) ................................... –0.3V to 6V
Analog Input Pins (CH1 to
CH20, COM) ................................. –0.3V to (V
DD
+ 0.3V)
Input Current (CH1 to CH20, 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
Q
1
, Q
2
, Q
3
, LDO, V
REFOUT
, V
REF_BVP
(Note 17)
Reference Short-Circuit Duration ..................... Indefinite
Operating Temperature Range
LTC2983C .................................................0ºC to 70ºC
LTC2983I ............................................. –40ºC to 85ºC
LTC2983H ...........................................–40ºC to 125ºC
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
25
26
27
28
29
30
31
32
33
34
35
36
T
JMAX
= 150°C,
θ
JA
= 57°C/W
The
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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
2983fc
–0.05
150
225
120
120
For more information
www.linear.com/LTC2983
3
LTC2983
COMPLETE SYSTEM ELECTRICAL CHARACTERISTICS
PARAMETER
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
50Hz (Notes 4, 8)
50Hz/60Hz (Notes 4, 6, 9)
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The
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denotes the specifications
TYP
MAX
UNITS
dB
dB
2.25
100
100
V
ms
ms
MIN
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 18)
H-Grade
(Notes 3, 15)
(Notes 3, 15)
(Note 5)
H-Grade
CONDITIONS
–F
S
≤ V
IN
≤ + F
S
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 30
Table 53
0.5
1.5
2.0
V
DD
– 0.3
25
37.5
Error within Noise Level of ADC
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
the full operating temperature range, otherwise specifications are at T
A
= 25°C.
The
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denotes the specifications which apply over
MIN
2.49
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TYP
3
3
MAX
2.51
15
20
10
5
5
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
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4.5
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30
115
60
30
70
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For more information
www.linear.com/LTC2983
LTC2983
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)
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All voltage values are with respect to GND.
Note 3:
Full scale ADC error. Measurements do not include reference error.
Note 4:
Guaranteed by design, not subject to test.
Note 5:
The input referred noise includes the contribution of internal
calibration operations.
Note 6:
MUX configuration delay = default 1ms
Note 7:
Global configuration set to 60Hz rejection.
Note 8:
Global configuration set to 50Hz rejection.
Note 9:
Global configuration default 50Hz/60Hz rejection.
Note 10:
The exact value of V
REF
is stored in the LTC2983 and used
for all measurement calculations. Temperature coefficient is measured
by dividing the maximum change in output voltage by the specified
temperature range.
Note 11:
Analog power-up. Command status register inaccessible during
this time.
Note 12:
Digital initialization. Begins at the conclusion of Analog Power-
Up. Command status register is 0
×
80 at the beginning of digital
initialization and 0
×
40 at the conclusion.
Note 13:
Long-term stability typically has a logarithmic characteristic
and therefore, changes after 1000 hours tend to be much smaller than
before that time. Total drift in the second thousand hours is normally less
CS,
SDI, SCK,
RESET
CS,
SDI, SCK,
RESET
CS,
SDI, SCK,
RESET
CS,
SDI, SCK,
RESET
I
O
= –800µA
I
O
= 1.6mA
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DIGITAL INPUTS AND DIGITAL OUTPUTS
CONDITIONS
The
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denotes the specifications which apply over the
MIN
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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
0.4
V
DD
– 0.5
–10
10
10
V
µA
pF
V
V
µA
than one third that of the first thousand hours with a continuing trend
toward reduced drift with time. Long-term stability will also be affected by
differential stresses between the IC and the board material created during
board assembly.
Note 14:
Hysteresis in output voltage is created by package stress
that differs depending on whether the IC was previously at a higher or
lower temperature. Output voltage is always measured at 25°C, but
the IC is cycled to the hot or cold temperature limit before successive
measurements. Hysteresis measures the maximum output change for the
averages of three hot or cold temperature cycles. For instruments that
are stored at well controlled temperatures (within 20 or 30 degrees of
operational temperature), it is usually not a dominant error source. Typical
hysteresis is the worst-case of 25°C to cold to 25°C or 25°C to hot to
25°C, preconditioned by one thermal cycle.
Note 15:
Differential Input Range is ±V
REF
/2.
Note 16:
RTD and thermistor measurements are made ratiometrically. As a
result current source excitation variation does not affect absolute accuracy.
Choose an excitation current such that largest sensor or R
SENSE
resistance
value, when driven by the nominal excitation current, will drop 1V or less.
The extended ADC input range will accommodate variation in excitation
current and the ratiometric calculation will negate the absolute value of the
excitation current.
Note 17:
Do not apply voltage or current sources to these pins. They must
be connected to capacitive loads only, otherwise permanent damage may
occur.
Note 18:
Input leakage measured with V
IN
= –10mV and V
IN
= 2.5V.
2983fc
For more information
www.linear.com/LTC2983
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