on October 24th 147

Understanding the MAX31855 Cold-Junction Converter: Pinout, Features, Applications, and Datasheet

The MAX31855 is a versatile thermocouple-to-digital converter known for its high accuracy and wide-ranging temperature measurement capabilities. It supports multiple thermocouple types, including K, J, and T, and delivers precise 14-bit data with the help of integrated cold-junction compensation. Its ability to measure extreme temperatures, ranging from -270°C to +1800°C, makes it ideal for demanding applications like industrial monitoring and scientific research. In addition, its compatibility with microcontroller systems through an SPI interface enhances ease of integration, positioning the MAX31855 as a reliable solution for precision temperature control and monitoring across various industries.

Catalog

MAX31855 Overview

The MAX31855 acts as a sophisticated link between thermocouples and digital systems, featuring a 14-bit ADC with integrated cold-junction compensation. It enhances the precision of temperature monitoring by connecting seamlessly with microcontrollers (µC). Various versions accommodate different thermocouple types, identifiable by suffixes such as MAX31855K.

Temperature Conversion

The MAX31855 processes thermocouple signals for ADC compatibility, minimizing noise interference. It compensates for environmental temperature variations by aligning thermal voltage to a 0°C benchmark. For K-type thermocouples, voltage shifts approximately 41µV/°C, expressed as

VOUT = (41.276µV/°C) x (TR - TAMB)

Each thermocouple type exhibits distinct traits, necessitating adjustments to address their non-linear performance.

Cold-Junction Compensation

This component identifies temperature disparities across the thermocouple junctions, managing these with cold-junction compensation by synchronizing its internal die temperature to the reference junction. By incorporating this temperature into the raw thermocouple data, it yields accurate "hot junction" readings. Placing the device strategically, so the cold junction and MAX31855 share similar temperatures, enriches measurement consistency. You can often position this in settings with stable temperatures, cherishing the reliability it brings to those who are deeply invested in the distinctions of thermal measurement.

Pin Configuration

CAD Model of MAX31855

Symbolic Representation

Board Layout

3D Model

Features

Feature	Description
Integration Reduces Design Time	Lowers system cost by simplifying the design process.
14-Bit, 0.25°C Resolution Converter	Provides high accuracy temperature measurements.
Integrated Cold-Junction Compensation	Automatically compensates for cold-junction temperature.
Supports Multiple Thermocouple Types	Compatible with K-, J-, N-, T-, S-, R-, and E-Type thermocouples.
Thermocouple Shorts Detection	Detects shorts to GND or VCC, improving system reliability.
Open Thermocouple Detection	Identifies when the thermocouple is disconnected.
Microcontroller Interface Compatibility	Easily interfaces with most microcontrollers.
SPI-Compatible Interface	Simple read-only SPI interface for easy data communication.

Technical Specification

Here’s the table based on the provided specifications for the Maxim Integrated MAX31855TASA+.

Type	Parameter
Factory Lead Time	6 Weeks
Mounting Type	Surface Mount
Package / Case	8-SOIC (0.154, 3.90mm Width)
Surface Mount	YES
Number of Pins	8
Weight	506.605978mg
Operating Temperature	-40°C ~ 125°C
Packaging	Tube
Published	2013
Pbfree Code	YES
Part Status	Active
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Number of Terminations	8
ECCN Code	EAR99
Type	Thermocouple to Digital Converter
Terminal Position	DUAL
Terminal Form	GULL WING
Peak Reflow Temperature (Cel)	NOT SPECIFIED
Number of Functions	1
Supply Voltage	3.3V
Terminal Pitch	1.27mm
Time @ Peak Reflow Temperature-Max (s)	NOT SPECIFIED
Base Part Number	MAX31855
Pin Count	8
Qualification Status	Not Qualified
Output Type	Digital
Operating Supply Voltage	3.3V
Interface	SPI
Max Supply Voltage	3.6V
Min Supply Voltage	3V
Operating Supply Current	900μA
Input Type	Thermocouple (Multiple)
Supply Current-Max (Isup)	1.5mA
Resolution	1.75 B
Length	4.9mm
Height Seated (Max)	1.75mm
Width	3.9mm
REACH SVHC	Unknown
RoHS Status	ROHS3 Compliant

Functional Block Diagram of MAX31855

Comparable Substitutes

Part Number	Descriptions	Manufacturer
MAX31855NASA+SIGNAL CIRCUITS	Analog Circuit, 1 Func, PDSO8, ROHS COMPLIANT, SOP-8	Maxim Integrated Products

Parts with Similar Specs of MAX31855

Part Number	Manufacturer	Package / Case	Number of Pins	Number of Terminations	Pbfree Code	RoHS Status	Packaging	Terminal Position
MAX31855TASA+	Maxim Integrated	8-SOIC (0.154, 3.90mm)	8	8	Yes	ROHS3 Compliant	Tube	DUAL
TC4427EOA	Microchip Technology	8-SOIC (0.154, 3.90mm)	8	8	Yes	ROHS3 Compliant	Tube	DUAL
TC7662BCOA	Microchip Technology	8-SOIC (0.154, 3.90mm)	8	8	Yes	ROHS3 Compliant	Tube	DUAL
MCP1404-E/SN	Microchip Technology	8-SOIC (0.154, 3.90mm)	8	8	Yes	ROHS3 Compliant	Tube	DUAL

Typical Application Circuit of MAX31855

Serial-Interface Diagrams of MAX31855

Timing

Protocols

Uses Variations

Industrial Systems

The impact of cutting-edge systems in industrial contexts lies in enhancing productivity and streamlining operations. Automation, data analytics, and IoT are integral to these advancements. A notable aspect is the focus on predictive maintenance leveraging machine learning to prevent disruptions. For instance, factories now employ sensors to continuously monitor equipment health, providing insights that forestall unexpected breakdowns. The transformation of smart factories has redefined industry approaches to innovation and market adaptation.

Home Appliances

Today's home appliances are more interconnected, playing a role in the evolving smart home landscape. Emphasizing energy efficiency and comfort, they harness to understand habits and optimize settings. Picture refrigerators alerting you to expiring items or washing machines calibrating water usage based on load size. These innovations enhance convenience while supporting sustainable living. The movement towards eco-friendly technologies mirrors societal values of mindful consumption.

HVAC Units

Heating, ventilation, and air conditioning systems contribute significantly to indoor environmental quality. Modern HVAC units use smart thermostats and sensors to adjust the temperature based on occupancy and weather, improving both comfort and energy consumption. The growing integration of renewable energy, like solar panels, highlights a move towards cutting carbon emissions. Innovations in air filtration also play a part in improving air quality and supporting health through preventive measures. The efficiency focus in HVAC systems aligns the desire for comfort with the pursuit of environmental stewardship.

MAX31855 Packaging and Dimensions

PACKAGE TYPE	PACKAGE CODE	OUTLINE NO.	LAND PATTERN NO.
8 SO	S8#4	21-0041	90-0096

About the Manufacturer

Maxim Integrated, now a basic part of Analog Devices, brings exceptional expertise in analog and mixed-signal integrated circuits. The company's dedication to sectors like automotive, industrial, and communications has positioned it as a prominent entity in these areas.

Their diverse array of products includes power management solutions, advanced sensors, and robust microcontrollers. These offerings aim to enhance efficiency and functionality, catering to the complex demands of modern electronic systems. Precision in sensor data processing, for instance, plays a major role in automotive safety features, emphasizing the need for meticulous design and execution.

Based in San Jose, California, Maxim Integrated has a remarkable global footprint with numerous facilities and offices across continents. This widespread presence facilitates collaboration with various industries and supports the seamless integration of their technologies in different regional settings. Forming local partnerships has been beneficial in developing solutions that align with specific regulatory and market requirements.

Datasheet PDF

TC4427EOA Datasheets:

TC442(6, 7, 8).pdf

TC7662BCOA Datasheets:

Analog and Interface Product Guide.pdf

MCP1404-E/SN Datasheets:

Cylindrical Battery Holders.pdf

Frequently Asked Questions [FAQ]

1. What is MAX31855?

The MAX31855 is a sophisticated integrated circuit designed to convert thermocouple signals into digital form. It integrates precise cold-junction compensation, yielding a 14-bit digital output via an SPI interface. Its role is notable in scenarios where temperature precision is active. In industrial environments, its dependability and precision are often likened to traditional methods, showcasing how digital data precision elevates automated processes. This transition from analog to digital streamlines temperature monitoring systems, bolstering their efficiency.

2. How do thermistors and thermocouples differ?

Thermistors and thermocouples are requisite in temperature measurement, each operating on distinct underlying principles. Thermistors change resistance with temperature fluctuations. They are highly sensitive and ideal for narrow ranges. Thermocouples generate a voltage between two different metals, allowing them to cover extensive temperature ranges and respond swiftly. Leveraging these sensors involves a deep understanding of their unique characteristics. This permits tailored selection for specific applications, significantly enhancing temperature monitoring efficacy in consumer electronics and intricate engineering systems.