MAX31855SASA+ - Maxim Integrated

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

Benets 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-

SCK

MICROCONTROLLER

MISO

SCK

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

Junction-to-Ambient Thermal Resistance (θJA) ........170°C/W

Junction-to-Case Thermal Resistance (θJC) ...............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

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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

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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

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Thermal Characteristics (continued)

Serial-Interface Timing Characteristics

Figure 1. Serial-Interface Protocol

Figure 2. Serial-Interface Timing

SCK

SO D31 D8 D7 D6 D5 D4 D3 D2 D1

D31 D0D1D2D3

SCK

tDV

tCSS

tDO

tTR

tCH tCL

MAX31855 Cold-Junction Compensated

Thermocouple-to-Digital Converter

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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

0.1

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

0.1

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

-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

-40

VCC = 3.6V

VCC = 3.3V

VCC = 3.0V

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MAX31855 Cold-Junction Compensated

Thermocouple-to-Digital Converter

Typical Operating Characteristics

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

SCKVCC

DNC

SOT-

T+

GND

TOP VIEW

MAX31855

ADC

DIGITAL

CONTROL

COLD-JUNCTION

COMPENSATION

FAULT

DETECTION

REFERENCE

VOLTAGE

S5 SCK

VCC

GND

T+

T-

MAX31855 Cold-Junction Compensated

Thermocouple-to-Digital Converter

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Pin DescriptionPin Conguration

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

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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

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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

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

(64°C)

…LSB 2-4

(0.0625°C) Reserved

1 =

Short

VCC

1 =

Short

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

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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

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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

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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 specications 1, 2, 3, 8, 12

2 2/12

Corrected the thermocouple temperature conditions in the Thermal Characteristics

table and Table 1; added clarication 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 Benets 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 specications 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.

│

MAX31855 Cold-Junction Compensated

Thermocouple-to-Digital Converter

Revision History

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MAX31855SASA+ MAX31855SASA+T MAX31855TASA+ MAX31855TASA+T