The Maxim 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, and a precision delta-sigma ADC converts the ratio of the RTD resistance to the reference resistance into digital form. The MAX31865 inputs resist overvoltage faults as large as ±50 V. Programmable detection of RTD open, cable open, and short conditions is included.
The MAX31865 simply and elegantly solves the common industrial design problem of digitizing a platinum RTD (such as a PT100 or PT1000) resistance, protects against ±50 V input overvoltages, and detects sensor and cable faults. In addition, the device simplifies resistance measurement by eliminating the precisely matched current sources used for 3-wire sensor connections in conventional designs. The built-in overvoltage protection (OVP) also eliminates the need for external protection circuitry, which lowers cost, reduces board space, and increases factory uptime.
- Simple conversion of platinum RTD resistance to digital value
- Handles 100 Ω to 1 kΩ (at 0°C) platinum RTDs (PT100 to PT1000)
- Compatible with 2-, 3-, and 4-wire sensor connections
- Conversion time: 21 ms max
- 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
- ±50 V input protection
- Fully differential VREF inputs
- Fault detection (open RTD element, RTD shorted to out-of-range voltage, or short across RTD element)
- SPI-compatible interface
- 20-pin TQFN package