max31855 Cold-Junction Converter:Pinout Benefits and Application
6 Weeks weeks 8-SOIC (0.154, 3.90mm Width) Tube Active Sensor & Detector Interface ICs Thermocouple to Digital Converter Surface Mount 1 (Unlimited) ROHS3 Compliant









6 Weeks weeks 8-SOIC (0.154, 3.90mm Width) Tube Active Sensor & Detector Interface ICs Thermocouple to Digital Converter Surface Mount 1 (Unlimited) ROHS3 Compliant
The MAX31855 performs cold-junction compensationand digitizes the signal from a K-, J-, N-, T-, S-, R-, orE-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.

Arduino MAX31855 Thermocouple Tutorial | SPI
- max31855 Descriptions
- max31855 Pinout
- max31855 CAD Model
- max31855 Features
- Specifications
- max31855 Functional Block Diagram
- max31855 Equivalent
- Parts with Similar Specs
- max31855 Pin Description
- max31855 Typical Application Circuit
- max31855 Serial-Interface Diagrams
- max31855 Application
- max31855 Package/Dimension
- max31855 Manufacturer
- Trend Analysis
- "Datasheet PDF
max31855 Descriptions
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 compensation sensing and correction, a digital controller, an SPIcompatible 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 thermocouple 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 convert 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 equivalent temperature values, it is necessary to compensate for the difference between the thermocouple coldjunction side (device ambient temperature) and a 0°C virtual reference. 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 temperature 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. The reference junction, or “cold” end (which should be at the 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 continues 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 compensation. It does this by first measuring its internal die temperature, which should be held at the same temperature as the reference junction. It then measures the voltage from the thermocouple’s output at the reference junction and converts this to the noncompensated thermocouple temperature value. This value is then added to the device’s die temperature to calculate the thermocouple’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
max31855 Pinout

max31855 Pinout
max31855 CAD Model

max31855 Symbol

max31855 Footprint

max31855 3D Model
max31855 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)
Specifications
- TypeParameter
- Factory Lead Time6 Weeks
- Mounting Type
The "Mounting Type" in electronic components refers to the method used to attach or connect a component to a circuit board or other substrate, such as through-hole, surface-mount, or panel mount.
Surface Mount - Package / Case
refers to the protective housing that encases an electronic component, providing mechanical support, electrical connections, and thermal management.
8-SOIC (0.154, 3.90mm Width) - Surface Mount
having leads that are designed to be soldered on the side of a circuit board that the body of the component is mounted on.
YES - Number of Pins8
- Weight506.605978mg
- Operating Temperature
The operating temperature is the range of ambient temperature within which a power supply, or any other electrical equipment, operate in. This ranges from a minimum operating temperature, to a peak or maximum operating temperature, outside which, the power supply may fail.
-40°C~125°C - Packaging
Semiconductor package is a carrier / shell used to contain and cover one or more semiconductor components or integrated circuits. The material of the shell can be metal, plastic, glass or ceramic.
Tube - Published2013
- Pbfree Code
The "Pbfree Code" parameter in electronic components refers to the code or marking used to indicate that the component is lead-free. Lead (Pb) is a toxic substance that has been widely used in electronic components for many years, but due to environmental concerns, there has been a shift towards lead-free alternatives. The Pbfree Code helps manufacturers and users easily identify components that do not contain lead, ensuring compliance with regulations and promoting environmentally friendly practices. It is important to pay attention to the Pbfree Code when selecting electronic components to ensure they meet the necessary requirements for lead-free applications.
yes - Part Status
Parts can have many statuses as they progress through the configuration, analysis, review, and approval stages.
Active - Moisture Sensitivity Level (MSL)
Moisture Sensitivity Level (MSL) is a standardized rating that indicates the susceptibility of electronic components, particularly semiconductors, to moisture-induced damage during storage and the soldering process, defining the allowable exposure time to ambient conditions before they require special handling or baking to prevent failures
1 (Unlimited) - Number of Terminations8
- ECCN Code
An ECCN (Export Control Classification Number) is an alphanumeric code used by the U.S. Bureau of Industry and Security to identify and categorize electronic components and other dual-use items that may require an export license based on their technical characteristics and potential for military use.
EAR99 - TypeThermocouple to Digital Converter
- Terminal Position
In electronic components, the term "Terminal Position" refers to the physical location of the connection points on the component where external electrical connections can be made. These connection points, known as terminals, are typically used to attach wires, leads, or other components to the main body of the electronic component. The terminal position is important for ensuring proper connectivity and functionality of the component within a circuit. It is often specified in technical datasheets or component specifications to help designers and engineers understand how to properly integrate the component into their circuit designs.
DUAL - Terminal Form
Occurring at or forming the end of a series, succession, or the like; closing; concluding.
GULL WING - Peak Reflow Temperature (Cel)
Peak Reflow Temperature (Cel) is a parameter that specifies the maximum temperature at which an electronic component can be exposed during the reflow soldering process. Reflow soldering is a common method used to attach electronic components to a circuit board. The Peak Reflow Temperature is crucial because it ensures that the component is not damaged or degraded during the soldering process. Exceeding the specified Peak Reflow Temperature can lead to issues such as component failure, reduced performance, or even permanent damage to the component. It is important for manufacturers and assemblers to adhere to the recommended Peak Reflow Temperature to ensure the reliability and functionality of the electronic components.
NOT SPECIFIED - Number of Functions1
- Supply Voltage
Supply voltage refers to the electrical potential difference provided to an electronic component or circuit. It is crucial for the proper operation of devices, as it powers their functions and determines performance characteristics. The supply voltage must be within specified limits to ensure reliability and prevent damage to components. Different electronic devices have specific supply voltage requirements, which can vary widely depending on their design and intended application.
3.3V - Terminal Pitch
The center distance from one pole to the next.
1.27mm - Time@Peak Reflow Temperature-Max (s)
Time@Peak Reflow Temperature-Max (s) refers to the maximum duration that an electronic component can be exposed to the peak reflow temperature during the soldering process, which is crucial for ensuring reliable solder joint formation without damaging the component.
NOT SPECIFIED - Base Part Number
The "Base Part Number" (BPN) in electronic components serves a similar purpose to the "Base Product Number." It refers to the primary identifier for a component that captures the essential characteristics shared by a group of similar components. The BPN provides a fundamental way to reference a family or series of components without specifying all the variations and specific details.
MAX31855 - Pin Count
a count of all of the component leads (or pins)
8 - Qualification Status
An indicator of formal certification of qualifications.
Not Qualified - Output Type
The "Output Type" parameter in electronic components refers to the type of signal or data that is produced by the component as an output. This parameter specifies the nature of the output signal, such as analog or digital, and can also include details about the voltage levels, current levels, frequency, and other characteristics of the output signal. Understanding the output type of a component is crucial for ensuring compatibility with other components in a circuit or system, as well as for determining how the output signal can be utilized or processed further. In summary, the output type parameter provides essential information about the nature of the signal that is generated by the electronic component as its output.
Digital - Operating Supply Voltage
The voltage level by which an electrical system is designated and to which certain operating characteristics of the system are related.
3.3V - Interface
In electronic components, the term "Interface" refers to the point at which two different systems, devices, or components connect and interact with each other. It can involve physical connections such as ports, connectors, or cables, as well as communication protocols and standards that facilitate the exchange of data or signals between the connected entities. The interface serves as a bridge that enables seamless communication and interoperability between different parts of a system or between different systems altogether. Designing a reliable and efficient interface is crucial in ensuring proper functionality and performance of electronic components and systems.
SPI - Max Supply Voltage
In general, the absolute maximum common-mode voltage is VEE-0.3V and VCC+0.3V, but for products without a protection element at the VCC side, voltages up to the absolute maximum rated supply voltage (i.e. VEE+36V) can be supplied, regardless of supply voltage.
3.6V - Min Supply Voltage
The minimum supply voltage (V min ) is explored for sequential logic circuits by statistically simulating the impact of within-die process variations and gate-dielectric soft breakdown on data retention and hold time.
3V - Operating Supply Current
Operating Supply Current, also known as supply current or quiescent current, is a crucial parameter in electronic components that indicates the amount of current required for the device to operate under normal conditions. It represents the current drawn by the component from the power supply while it is functioning. This parameter is important for determining the power consumption of the component and is typically specified in datasheets to help designers calculate the overall power requirements of their circuits. Understanding the operating supply current is essential for ensuring proper functionality and efficiency of electronic systems.
900μA - Input Type
Input type in electronic components refers to the classification of the signal or data that a component can accept for processing or conversion. It indicates whether the input is analog, digital, or a specific format such as TTL or CMOS. Understanding input type is crucial for ensuring compatibility between different electronic devices and circuits, as it determines how signals are interpreted and interacted with.
Thermocouple (Multiple) - Supply Current-Max (Isup)
Supply Current-Max (Isup) refers to the maximum amount of current that an electronic component can draw from its power supply during operation. It represents the peak current demand of the device under normal operating conditions and is critical for ensuring that the power supply can adequately support the component's needs without risking damage or malfunction. This parameter is essential for designing circuits and selecting appropriate power supply units to prevent overloading and ensure reliable performance.
1.5mA - Resolution
Resolution in electronic components refers to the smallest increment of measurement or change that can be detected or represented by the component. It is a crucial specification in devices such as sensors, displays, and converters, as it determines the level of detail or accuracy that can be achieved. For example, in a digital camera, resolution refers to the number of pixels that make up an image, with higher resolution indicating a greater level of detail. In analog-to-digital converters, resolution is the number of discrete values that can be represented in the digital output, determining the precision of the conversion process. Overall, resolution plays a significant role in determining the performance and capabilities of electronic components in various applications.
1.75 B - Length4.9mm
- Height Seated (Max)
Height Seated (Max) is a parameter in electronic components that refers to the maximum allowable height of the component when it is properly seated or installed on a circuit board or within an enclosure. This specification is crucial for ensuring proper fit and alignment within the overall system design. Exceeding the maximum seated height can lead to mechanical interference, electrical shorts, or other issues that may impact the performance and reliability of the electronic device. Manufacturers provide this information to help designers and engineers select components that will fit within the designated space and function correctly in the intended application.
1.75mm - Width3.9mm
- REACH SVHC
The parameter "REACH SVHC" in electronic components refers to the compliance with the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) regulation regarding Substances of Very High Concern (SVHC). SVHCs are substances that may have serious effects on human health or the environment, and their use is regulated under REACH to ensure their safe handling and minimize their impact.Manufacturers of electronic components need to declare if their products contain any SVHCs above a certain threshold concentration and provide information on the safe use of these substances. This information allows customers to make informed decisions about the potential risks associated with using the components and take appropriate measures to mitigate any hazards.Ensuring compliance with REACH SVHC requirements is essential for electronics manufacturers to meet regulatory standards, protect human health and the environment, and maintain transparency in their supply chain. It also demonstrates a commitment to sustainability and responsible manufacturing practices in the electronics industry.
Unknown - RoHS Status
RoHS means “Restriction of Certain Hazardous Substances” in the “Hazardous Substances Directive” in electrical and electronic equipment.
ROHS3 Compliant
max31855 Functional Block Diagram

max31855 Functional Block Diagram
max31855 Equivalent
| Part Number | Descriptions | Manufacturer |
| MAX31855NASA+SIGNAL CIRCUITS | Analog Circuit, 1 Func, PDSO8, ROHS COMPLIANT, SOP-8 | Maxim Integrated Products |
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max31855 Pin Description

max31855 Pin Description
max31855 Typical Application Circuit

max31855 Typical Application Circuit
max31855 Serial-Interface Diagrams

max31855 Serial-Interface Timing

max31855 Serial-Interface protocol
max31855 Application
● Industrial
● Appliances
● HVAC
max31855 Package/Dimension

max31855 Package/Dimension
max31855 Manufacturer
Maxim Integrated, a subsidiary of Analog Devices, designs, manufactures and sells analog and mixed-signal integrated circuits for the automotive, industrial, communications, consumer, and computing markets. Maxim's product portfolio includes power and battery management ICs, sensors, analog ICs, interface ICs, communications solutions, digital ICs, embedded security, and microcontrollers. The company is headquartered in San Jose, California, and has design centers, manufacturing facilities, and sales offices worldwide.
Trend Analysis
"Datasheet PDF
What is MAX31855?
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.
What is the difference between a thermistor and a thermocouple?
A thermistor is a thermally sensitive resistor that exhibits a continuous, small, incremental change in resistance correlated to temperature variations. Thermocouples reflect proportional changes in temperature through the varying voltage created between two dissimilar metals electrically bonded together.
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