MAX31855 Datasheet by Maxim Integrated

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General Description
The MAX31855 performs cold-junction compensation
and digitizes the signal from a K-, J-, N-, T-, S-, R-, or
E-type thermocouple. The data is output in a signed
14-bit, SPI-compatible, read-only format. This converter
resolves temperatures to 0.25°C, allows readings as
high as +1800°C and as low as -270°C, and exhibits
thermocouple accuracy of ±2°C for temperatures ranging
from -200°C to +700°C for K-type thermocouples. For full
range accuracies and other thermocouple types, see the
Thermal Characteristics specifications.
Applications
Industrial
Appliances
HVAC
Benefits and Features
Integration Reduces Design Time and Lowers
System Cost
14-Bit, 0.25°C Resolution Converter
Integrated Cold-Junction Compensation
Versions Available for Most Common
Thermocouple
Types: K-, J-, N-, T-, S-, R-, and E-Type
Detects Thermocouple Shorts to GND or VCC
Detects Open Thermocouple
Interfaces to Most Microcontrollers
Simple SPI-Compatible Interface (Read-Only)
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part, refer
to www.maximintegrated.com/MAX31855.related.
19-5793; Rev 5; 1/15
VCC
GND
T+
T-
SO
SCK
CS
MICROCONTROLLER
MISO
SCK
SS
0.1µF
MAX31855
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
Typical Application Circuit
Supply Voltage Range (VCC to GND)...................-0.3V to +4.0V
All Other Pins............................................. -0.3V to (VCC + 0.3V)
Continuous Power Dissipation (TA = +70°C)
SO (derate 5.9mW/°C above +70°C).......................470.6mW
ESD Protection (All Pins, Human Body Model)....................±2kV
Operating Temperature Range......................... -40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range ........................... -65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
Soldering Temperature (reflow) ......................................+260°C
SO
Junction-to-Ambient Thermal Resistance JA) ........170°C/W
Junction-to-Case Thermal Resistance JC) ...............40°C/W
(Note 1)
(TA = -40°C to +125°C, unless otherwise noted.)
(3.0V ≤ VCC P 3.6V, TA = -40°C to +125°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Power-Supply Voltage VCC (Note 2) 3.0 3.3 3.6 V
Input Logic 0 VIL -0.3 +0.8 V
Input Logic 1 VIH 2.1 VCC +
0.3 V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Power-Supply Current ICC 900 1500 µA
Thermocouple Input Bias Current TA = -40°C to +125°C, 100mV across the
thermocouple inputs -100 +100 nA
Power-Supply Rejection -0.3 °C/V
Power-On Reset Voltage
Threshold VPOR (Note 3) 2 2.5 V
Power-On Reset Voltage
Hysteresis 0.2 V
Output High Voltage VOH IOUT = -1.6mA VCC -
0.4 V
Output Low Voltage VOL IOUT = 1.6mA 0.4 V
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
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Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Package Thermal Characteristics
Recommended Operating Conditions
DC Electrical Characteristics
(3.0V ≤ VCC P 3.6V, TA = -40°C to +125°C, unless otherwise noted.) (Note 4)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX31855K Thermocouple
Temperature Gain and Offset
Error (41.276µV/°C nominal
sensitivity) (Note 4)
TTHERMOCOUPLE = -200°C to +700°C,
TA = -20°C to +85°C (Note 3) -2 +2
°C
TTHERMOCOUPLE = +700°C to +1350°C,
TA = -20°C to +85°C (Note 3) -4 +4
TTHERMOCOUPLE = -270°C to +1372°C,
TA = -40°C to +125°C (Note 3) -6 +6
MAX31855J Thermocouple
Temperature Gain and Offset
Error (57.953µV/°C nominal
sensitivity) (Note 4)
TTHERMOCOUPLE = -210°C to +750°C,
TA = -20°C to +85°C (Note 3) -2 +2
°C
TTHERMOCOUPLE = -210°C to +1200°C,
TA = -40°C to +125°C (Note 3) -4 +4
MAX31855N Thermocouple
Temperature Gain and Offset
Error (36.256µV/°C nominal
sensitivity) (Note 4)
TTHERMOCOUPLE = -200°C to +700°C,
TA = -20°C to +85°C (Note 3) -2 +2
°C
TTHERMOCOUPLE = +700°C to +1300°C,
TA = -20°C to +85°C (Note 3) -4 +4
TTHERMOCOUPLE = -270°C to +1300°C,
TA = -40°C to +125°C (Note 3) -6 +6
MAX31855T Thermocouple
Temperature Gain and Offset
Error (52.18µV/°C nominal
sensitivity) (Note 4)
TTHERMOCOUPLE = -270°C to +400°C,
TA = -20°C to +85°C (Note 3) -2 +2
°C
TTHERMOCOUPLE = -270°C to +400°C,
TA = -40°C to +125°C (Note 3) -4 +4
MAX31855E Thermocouple
Temperature Gain and Offset
Error (76.373µV/°C nominal
sensitivity) (Note 4)
TTHERMOCOUPLE = -200°C to +700°C,
TA = -20°C to +85°C (Note 3) -2 +2
°C
TTHERMOCOUPLE = +700°C to +1000°C,
TA = -20°C to +85°C (Note 3) -3 +3
TTHERMOCOUPLE = -270°C to +1000°C,
TA = -40°C to +125°C (Note 3) -5 +5
MAX31855R Thermocouple
Temperature Gain and Offset
Error (10.506µV/°C nominal
sensitivity) (Note 4)
TTHERMOCOUPLE = -50°C to +700°C,
TA = -20°C to +85°C (Note 3) -2 +2
°C
TTHERMOCOUPLE = +700°C to +1768°C,
TA = -20°C to +85°C (Note 3) -4 +4
TTHERMOCOUPLE = -50°C to +1768°C,
TA = -40°C to +125°C (Note 3) -6 +6
MAX31855S Thermocouple
Temperature Gain and Offset
Error (9.587µV/°C nominal
sensitivity) (Note 4)
TTHERMOCOUPLE = -50°C to +700°C,
TA = -20°C to +85°C (Note 3) -2 +2
°C
TTHERMOCOUPLE = +700°C to +1768°C,
TA = -20°C to +85°C (Note 3) -4 +4
TTHERMOCOUPLE = -50°C to +1768°C,
TA = -40°C to +125°C (Note 3) -6 +6
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
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Thermal Characteristics
(3.0V ≤ VCC P 3.6V, TA = -40°C to +125°C, unless otherwise noted.) (Note 4)
(See Figure 1 and Figure 2.)
Note 2: All voltages are referenced to GND. Currents entering the IC are specified positive, and currents exiting the IC are negative.
Note 3: Guaranteed by design; not production tested.
Note 4: Not including cold-junction temperature error or thermocouple nonlinearity.
Note 5: Specification is 100% tested at TA = +25°C. Specification limits over temperature (TA = TMIN to TMAX) are guaranteed by
design and characterization; not production tested.
Note 6: Because the thermocouple temperature conversions begin at VPOR, depending on VCC slew rates, the first thermocouple
temperature conversion may not produce an accurate result. Therefore, the tCONV_PU specification is required after VCC is
greater than VCCMIN to guarantee a valid thermocouple temperature conversion result.
Note 7: For all pins except T+ and T- (see the Thermocouple Input Bias Current parameter in the DC Electrical Characteristics
table).
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Thermocouple Temperature Data
Resolution 0.25 °C
Internal Cold-Junction
Temperature Error
TA = -20°C to +85°C (Note 3) -2 +2 °C
TA = -40°C to +125°C (Note 3) -3 +3
Cold-Junction Temperature Data
Resolution TA = -40°C to +125°C 0.0625 °C
Temperature Conversion Time
(Thermocouple, Cold Junction,
Fault Detection)
tCONV (Note 5) 70 100 ms
Thermocouple Conversion
Power-Up Time tCONV_PU (Note 6) 200 ms
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Leakage Current ILEAK (Note 7) -1 +1 µA
Input Capacitance CIN 8 pF
Serial-Clock Frequency fSCL 5 MHz
SCK Pulse-High Width tCH 100 ns
SCK Pulse-Low Width tCL 100 ns
SCK Rise and Fall Time 200 ns
CS Fall to SCK Rise tCSS 100 ns
SCK to CS Hold 100 ns
CS Fall to Output Enable tDV 100 ns
CS Rise to Output Disable tTR 40 ns
SCK Fall to Output Data Valid tDO 40 ns
CS Inactive Time (Note 3) 200 ns
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
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Thermal Characteristics (continued)
Serial-Interface Timing Characteristics
mm mm
Figure 1. Serial-Interface Protocol
Figure 2. Serial-Interface Timing
CS
SCK
SO D31 D8 D7 D6 D5 D4 D3 D2 D1
D0
D31 D0D1D2D3
SCK
SO
tDV
tCSS
tDO
CS
tTR
tCH tCL
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
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Serial-Interface Diagrams
(VCC = +3.3V, TA = +25°C, unless otherwise noted.)
INTERNAL TEMPERATURE SENSOR
ACCURACY
MAX31855 toc02
TEMPERATURE (°C)
MEASUREMENT ERROR (°C)
806020 400-20
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
-0.2
-40 100
VCC = 3.3V
NOTE: THIS DATA WAS TAKEN
IN PRECISION BATH SO HIGH
TEMPERATURE LIMIT IS 90°C
ADC ACCURACY vs. ADC INPUT VOLTAGE
ACROSS TEMPERATURE
MAX31855 toc03
ADC INPUT VOLTAGE (mV)
ADC ACCURACY (°C)
4020
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
-0.7
0 60
AT -40°C
VCC = 3.3V
AT +85°C
AT +25°C
ADC ACCURACY vs. ADC INPUT VOLTAGE
ACROSS VCC
MAX31855 toc04
ADC INPUT VOLTAGE (mV)
ADC ACCURACY (°C)
4020
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
-1.0
0 60
VCC = 3.6V
VCC = 3.3V
VCC = 3.0V
INTERNAL TEMPERATURE = +25°C
SUPPLY CURRENT vs. TEMPERATURE
MAX31855 toc01
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
100 120806040200-20
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0
-40
VCC = 3.6V
VCC = 3.3V
VCC = 3.0V
Maxim Integrated
6
www.maximintegrated.com
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
Typical Operating Characteristics
3311 g, CCCC
PIN NAME FUNCTION
1 GND Ground
2T- Thermocouple Input. See Table 1. Do not
connect to GND.
3 T+ Thermocouple Input. See Table 1.
4 VCC Power-Supply Voltage
5 SCK Serial-Clock Input
6CS Active-Low Chip Select. Set CS low to
enable the serial interface.
7 SO Serial-Data Output
8 DNC Do Not Connect
CS
SCKVCC
1
+
2
8
7
DNC
SOT-
T+
GND
SO
TOP VIEW
3
4
6
5
MAX31855
MAX31855
ADC
DIGITAL
CONTROL
COLD-JUNCTION
COMPENSATION
FAULT
DETECTION
REFERENCE
VOLTAGE
S4
S1
S2
S3
S5 SCK
VCC
VCC
SO
CS
GND
T+
T-
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
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Pin DescriptionPin Configuration
Block Diagram
Detailed Description
The MAX31855 is a sophisticated thermocouple-to-digital
converter with a built-in 14-bit analog-to-digital converter
(ADC). The device also contains cold-junction compensa-
tion sensing and correction, a digital controller, an SPI-
compatible interface, and associated control logic. The
device is designed to work in conjunction with an external
microcontroller (µC) in thermostatic, process-control, or
monitoring applications. The device is available in several
versions, each optimized and trimmed for a specific thermo-
couple type (K, J, N, T, S, R, or E.). The thermocouple type is
indicated in the suffix of the part number (e.g., MAX31855K).
See the Ordering Information table for all options.
Temperature Conversion
The device includes signal-conditioning hardware to con-
vert the thermocouple’s signal into a voltage compatible
with the input channels of the ADC. The T+ and T- inputs
connect to internal circuitry that reduces the introduction
of noise errors from the thermocouple wires.
Before converting the thermoelectric voltages into equiva-
lent temperature values, it is necessary to compensate
for the difference between the thermocouple coldjunction
side (device ambient temperature) and a 0°C virtual ref-
erence. For a K-type thermocouple, the voltage changes
by about 41µV/°C, which approximates the thermocouple
characteristic with the following linear equation:
VOUT = (41.276µV/°C) x (TR - TAMB)
where VOUT is the thermocouple output voltage (µV), TR
is the temperature of the remote thermocouple junction
(°C), and TAMB is the temperature of the device (°C).
Other thermocouple types use a similar straight-line
approximation but with different gain terms. Note that the
MAX31855 assumes a linear relationship between tem-
perature and voltage. Because all thermocouples exhibit
some level of nonlinearity, apply appropriate correction to
the device’s output data.
Cold-Junction Compensation
The function of the thermocouple is to sense a difference
in temperature between two ends of the thermocouple
wires. The thermocouple’s “hot” junction can be read
across the operating temperature range (Table 1). The
reference junction, or “cold” end (which should be at the
Table 1. Thermocouple Wire Connections and Nominal Sensitivities
TYPE T- WIRE T+ WIRE TEMP RANGE (°C) SENSITIVITY (µV/°C)
COLD-JUNCTION
SENSITIVITY (µV/°C)
(0°C TO +70°C)
KAlumel Chromel -270 to +1372 41.276
(0°C to +1000°C) 40.73
JConstantan Iron -210 to +1200 57.953
(0°C to +750°C) 52.136
NNisil Nicrosil -270 to + 1300 36.256
(0°C to +1000°C) 27.171
SPlatinum Platinum/Rhodium -50 to +1768 9.587
(0°C to +1000°C) 6.181
TConstantan Copper -270 to +400 52.18
(0°C to +400°C) 41.56
EConstantan Chromel -270 to +1000 76.373
(0°C to +1000°C) 44.123
RPlatinum Platinum/Rhodium -50 to +1768 10.506
(0°C to +1000°C) 6.158
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
8
same temperature as the board on which the device is
mounted) can range from -55°C to +125°C. While the
temperature at the cold end fluctuates, the device contin-
ues to accurately sense the temperature difference at the
opposite end.
The device senses and corrects for the changes in the
reference junction temperature with cold-junction com-
pensation. It does this by first measuring its internal die
temperature, which should be held at the same tem-
perature as the reference junction. It then measures the
voltage from the thermocouple’s output at the reference
junction and converts this to the noncompensated ther-
mocouple temperature value. This value is then added
to the device’s die temperature to calculate the thermo-
couple’s “hot junction” temperature. Note that the “hot
junction” temperature can be lower than the cold junction
(or reference junction) temperature.
Optimal performance from the device is achieved when
the thermocouple cold junction and the device are at the
same temperature. Avoid placing heat-generating devices
or components near the MAX31855 because this could
produce cold-junction-related errors.
Conversion Functions
During the conversion time, tCONV, three functions are
performed: the temperature conversion of the internal
cold-junction temperature, the temperature conversion of
the external thermocouple, and the detection of thermo-
couple faults.
When executing the temperature conversion for the inter-
nal cold-junction compensation circuit, the connection to
signal from the external thermocouple is opened (switch
S4) and the connection to the cold-junction compensa-
tion circuit is closed (switch S5). The internal T- reference
to ground is still maintained (switch S3 is closed) and
the connections to the fault-detection circuit are open
(switches S1 and S2).
When executing the temperature conversion of the
external thermocouple, the connections to the internal
fault-detection circuit are opened (switches S1 and S2 in
the Block Diagram) and the switch connecting the cold-
junction compensation circuit is opened (switch S5). The
internal ground reference connection (switch S3) and the
connection to the ADC (switch S4) are closed. This allows
the ADC to process the voltage detected across the T+
and T- terminals.
During fault detection, the connections from the external
thermocouple and cold-junction compensation circuit to
the ADC are opened (switches S4 and S5). The internal
ground reference on T- is also opened (switch S3). The
connections to the internal fault-detection circuit are
closed (switch S1 and S2). The fault-detection circuit tests
for shorted connections to VCC or GND on the T+ and T-
inputs, as well as looking for an open thermocouple condi-
tion. Bits D0, D1, and D2 of the output data are normally
low. Bit D2 goes high to indicate a thermocouple short to
VCC, bit D1 goes high to indicate a thermocouple short
to GND, and bit D0 goes high to indicate a thermocouple
open circuit. If any of these conditions exists, bit D16 of
the SO output data, which is normally low, also goes high
to indicate that a fault has occurred.
Serial Interface
The Typical Application Circuit shows the device inter-
faced with a microcontroller. In this example, the device
processes the reading from the thermocouple and trans-
mits the data through a serial interface. Drive CS low
and apply a clock signal at SCK to read the results at
SO. Conversions are always being performed in the
background. The fault and temperature data are only be
updated when CS is high.
Drive CS low to output the first bit on the SO pin. A com-
plete serial-interface read of the cold-junction compen-
sated thermocouple temperature requires 14 clock cycles.
Thirty-two clock cycles are required to read both the
thermocouple and reference junction temperatures (Table
2 and Table 3.) The first bit, D31, is the thermocouple
temperature sign bit, and is presented to the SO pin within
tDV of the falling edge of CS. Bits D[30:18] contain the
converted temperature in the order of MSB to LSB, and
are presented to the SO pin within tD0 of the falling edge
of SCK. Bit D16 is normally low and goes high when the
thermocouple input is open or shorted to GND or VCC.
The reference junction temperature data begins with D15.
CS can be taken high at any point while clocking out con-
version data. If T+ and T- are unconnected, the thermo-
couple temperature sign bit (D31) is 0, and the remainder
of the thermocouple temperature value (D[30:18]) is 1.
Figure 1 and Figure 2 show the serial-interface timing and
order. Table 2 and Table 3 show the SO output bit weights
and functions.
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
9
Note: The practical temperature ranges vary with the thermo-
couple type.
Table 2. Memory Map—Bit Weights and Functions
Table 3. Memory Map—Descriptions
Table 4. Thermocouple Temperature Data
Format
Table 5. Reference Junction Temperature
Data Format
14-BIT THERMOCOUPLE
TEMPERATURE DATA RES FAULT
BIT
12-BIT INTERNAL TEMPERATURE
DATA RES SCV
BIT
SCG
BIT
OC
BIT
BIT D31 D30 D18 D17 D16 D15 D14 … D4 D3 D2 D1 D0
VALUE Sign MSB 210
(1024°C) LSB 2-2
(0.25°C) Reserved 1 =
Fault Sign
MSB
26
(64°C)
LSB 2-4
(0.0625°C) Reserved
1 =
Short
to
VCC
1 =
Short
to
GND
1 =
Open
Circuit
BIT NAME DESCRIPTION
D[31:18] 14-Bit Thermocouple
Temperature Data These bits contain the signed 14-bit thermocouple temperature value. See Table 4.
D17 Reserved This bit always reads 0.
D16 Fault This bit reads at 1 when any of the SCV, SCG, or OC faults are active. Default value
is 0.
D[15:4] 12-Bit Internal Temperature
Data
These bits contain the signed 12-bit value of the reference junction temperature. See
Table 5.
D3 Reserved This bit always reads 0.
D2 SCV Fault This bit is a 1 when the thermocouple is short-circuited to VCC. Default value is 0.
D1 SCG Fault This bit is a 1 when the thermocouple is short-circuited to GND. Default value is 0.
D0 OC Fault This bit is a 1 when the thermocouple is open (no connections). Default value is 0.
TEMPERATURE
(°C)
DIGITAL OUTPUT
(D[31:18])
+1600.00 0110 0100 0000 00
+1000.00 0011 1110 1000 00
+100.75 0000 0110 0100 11
+25.00 0000 0001 1001 00
0.00 0000 0000 0000 00
-0.25 1111 1111 1111 11
-1.00 1111 1111 1111 00
-250.00 1111 0000 0110 00
TEMPERATURE
(°C)
DIGITAL OUTPUT
(D[15:4])
+127.0000 0111 1111 0000
+100.5625 0110 0100 1001
+25.0000 0001 1001 0000
0.0000 0000 0000 0000
-0.0625 1111 1111 1111
-1.0000 1111 1111 0000
-20.0000 1110 1100 0000
-55.0000 1100 1001 0000
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
10
Applications Information
Noise Considerations
Because of the small signal levels involved, thermocouple
temperature measurement is susceptible to powersupply
coupled noise. The effects of power-supply noise can be
minimized by placing a 0.1µF ceramic bypass capacitor
close to the VCC pin of the device and to GND.
The input amplifier is a low-noise amplifier designed
to enable high-precision input sensing. Keep the ther-
mocouple and connecting wires away from electrical
noise sources. It is strongly recommended to add a
10nF ceramic surface-mount differential capacitor, placed
across the T+ and T- pins, in order to filter noise on the
thermocouple lines.
Thermal Considerations
Self-heating degrades the device’s temperature measure-
ment accuracy in some applications. The magnitude of
the temperature errors depends on the thermal conduc-
tivity of the device package, the mounting technique, and
the effects of airflow. Use a large ground plane to improve
the device’s temperature measurement accuracy.
The thermocouple system’s accuracy can also be
improved by following these precautions:
Use the largest wire possible that does not shunt heat
away from the measurement area.
If a small wire is required, use it only in the region
of the measurement, and use extension wire for the
region with no temperature gradient.
• Avoid mechanical stress and vibration, which could
strain the wires.
When using long thermocouple wires, use a twisted
pair extension wire.
Avoid steep temperature gradients.
Try to use the thermocouple wire well within its tem-
perature rating.
Use the proper sheathing material in hostile environ-
ments to protect the thermocouple wire.
Use extension wire only at low temperatures and only
in regions of small gradients.
Keep an event log and a continuous record of thermo-
couple resistance.
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
11
Note: All devices are specified over the -40°C to +125°C operating temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
PART THERMOCOUPLE TYPE MEASURED TEMP RANGE PIN-PACKAGE
MAX31855KASA+ K -200°C to +1350°C 8 SO
MAX31855KASA+T K -200°C to +1350°C 8 SO
MAX31855JASA+ J -40°C to +750°C 8 SO
MAX31855JASA+T J -40°C to +750°C 8 SO
MAX31855NASA+ N -200°C to + 1300°C 8 SO
MAX31855NASA+T N -200°C to + 1300°C 8 SO
MAX31855SASA+ S -50°C to +1600°C 8 SO
MAX31855SASA+T S -50°C to +1600°C 8 SO
MAX31855TASA+ T -250°C to +400°C 8 SO
MAX31855TASA+T T -250°C to +400°C 8 SO
MAX31855EASA+ E -40°C to +900°C 8 SO
MAX31855EASA+T E -40°C to +900°C 8 SO
MAX31855RASA+ R -50°C to +1770°C 8 SO
MAX31855RASA+T R -50°C to +1770°C 8 SO
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
8 SO S8+4 21-0041 90-0096
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com Maxim Integrated
12
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Ordering Information
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 3/11 Initial release
111/11 Corrected ESD protection value; added “S” and “R” type specifications 1, 2, 3, 8, 12
2 2/12
Corrected the thermocouple temperature conditions in the Thermal Characteristics
table and Table 1; added clarification to the Serial Interface section to help users better
understand how to communicate with the device; added a recommendation to add a
10nF differential capacitor to the T+/T- pins in the Noise Considerations section
3, 8, 9, 11
3 7/14 Change “S” type thermocouple minimum temperature in Table 1 and Ordering
Information 8, 12
4 11/14 Removed automotive reference from data sheet 1
5 1/15 Revised Benefits and Features section 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2015 Maxim Integrated Products, Inc.
13
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

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