RTD-to-Digital Converter

Complete Solution Provides a Digital Temperature Reading from an RTD with Fault Detection and Input Voltage Protection


The MAX31865 is an easy-to-use resistance-to-digital converter optimized for platinum resistance temperature detectors (RTDs). An external resistor sets the sensitivity for the RTD being used and a precision delta-sigma ADC converts the ratio of the RTD resistance to the reference resistance into digital form. The MAX31865's inputs are protected against overvoltage faults as large as ±45V. Programmable detection of RTD and cable open and short conditions is included.

MAX31865: Block Diagram MAX31865: Block Diagram Enlarge+

Key Features

  • Integration Lowers System Cost, Simplifies Design Efforts, and Reduces Design Cycle Time
    • Simple Conversion of Platinum RTD Resistance to Digital Value
    • Handles 100Ω to 1kΩ (at 0°C) Platinum RTDs (PT100 to PT1000)
    • Compatible with 2-, 3-, and 4-Wire Sensor Connections
    • SPI-Compatible Interface
    • 20-Pin TQFN and SSOP Packages
  • High Accuracy Facilitates Meeting Error Budgets
    • 15-Bit ADC Resolution; Nominal Temperature Resolution 0.03125°C (Varies Due to RTD Nonlinearity)
    • Total Accuracy Over All Operating Conditions: 0.5°C (0.05% of Full Scale) max
    • Fully Differential VREF Inputs
    • 21ms (max) Conversion Time
  • Integrated Fault Detection Increases System Reliability
    • ±45V Input Protection
    • Fault Detection (Open RTD Element, RTD Shorted to Out-of-Range Voltage, or Short Across RTD Element)


  • Industrial Equipment
  • Instrumentation
  • Medical Equipment
Part Number Sensor Type Functions Interface Channels Accuracy
Parasite Pwr. Temp. Resolution
Oper. Temp.
Package/Pins Budgetary
See Notes
MAX31865  Remote
RTD-to-Digital Converter
Thermistor-to-Digital Converter
SPI One 0.5 No 15 -40 to +125
$3.00 @1k
See All Temperature Sensors (112)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX31865EVKIT: Evaluation Kit for the MAX31865
MAX31865PMB1: Peripheral Module for the MAX31865

Technical Documents

User Guide 6041 MAXREFDES42# IO-Link RTD Temp Sensor Quick Start Guide (IQ2 IO-Link Master Version)

Quality and Environmental Data

Product Reliability Reports: MAX31865.pdf 
Lead-Free Package Tin (Sn) Whisker Reports

Tools & Models

MAX31865 IBIS Model


Related Resources