MAX31865 RTD-to-Digital Converter General Description Benefits and Features The MAX31865 is an easy-to-use resistance-to-digital Integration Lowers System Cost, Simplifies Design converter optimized for platinum resistance temperature Efforts, and Reduces Design Cycle Time detectors (RTDs). An external resistor sets the sensitivity Simple Conversion of Platinum RTD Resistance to for the RTD being used and a precision delta-sigma ADC Digital Value converts the ratio of the RTD resistance to the reference Handles 100 to 1k (at 0C) Platinum RTDs (PT100 to PT1000) resistance into digital form. The MAX31865s inputs are protected against overvoltage faults as large as Q45V. Compatible with 2-, 3-, and 4-Wire Sensor Connections SPI-Compatible Interface Programmable detection of RTD and cable open and short conditions is included. 20-Pin TQFN and SSOP Packages High Accuracy Facilitates Meeting Error Budgets Applications 15-Bit ADC Resolution Nominal Temperature Industrial Equipment Resolution 0.03125NC (Varies Due to RTD Nonlin- Medical Equipment earity) Instrumentation Total Accuracy Over All Operating Conditions: 0.5NC (0.05% of Full Scale) max Fully Differential V Inputs REF 21ms (max) Conversion Time Integrated Fault Detection Increases System Reliability Ordering Information appears at end of data sheet. 45V Input Protection Fault Detection (Open RTD Element, RTD Shorted to Out-of-Range Voltage, or Short Across RTD Element) Typical Application Circuits V V DD DD 4-WIRE SENSOR CONNECTION 0.1F 0.1F BIAS REFIN+ R REF DRDY REFIN- SDI ISENSOR R CABLE MAX31865 HOST SCLK FORCE+ INTERFACE FORCE2 CS R CABLE SDO RTDIN+ N.C. C * I RTD R CABLE RTDIN- FORCE- *C = 10nF FOR 1k RTD I R CABLE 100nF FOR 100 RTD Typical Application Circuits continued at end of data sheet. 19-6478 Rev 3 7/15 GND1 DVDD GND2 V DD DGNDMAX31865 RTD-to-Digital Converter Absolute Maximum Ratings Voltage Range on V Relative to GND1 ............-0.3V to +4.0V Continuous Power Dissipation (T = +70NC) DD A Voltage Range on BIAS, REFIN+, TQFN (derate 34.5mW/NC above +70NC)...............2758.6mW SSOP (derate 11.9mW/C above +70 C)...............952.4mW REFIN-, ISENSOR ................................. -0.3V to (V + 0.3V) DD ESD Protection (all pins, Human Body Model) ...................2kV Voltage Range on FORCE+, FORCE2, Operating Temperature Range ........................ -40NC to +125NC FORCE-, RTDIN+, RTDIN- Relative to GND1 ....-50V to +50V Junction Temperature .....................................................+150NC Voltage Range on DVDD Relative to DGND ........-0.3V to +4.0V Storage Temperature Range ............................ -65NC to +150NC Voltage Range on All Digital Pins Soldering Temperature (reflow) ......................................+260NC Relative to DGND ............................. -0.3V to (V + 0.3V) DVDD Lead Temperature (soldering,10s) .................................+300NC 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 (Note 1) TQFN SSOP Junction-to-Ambient Thermal Resistance (q ) ..........29C/W Junction-to-Ambient Thermal Resistance (q ) ..........84C/W JA JA Junction-to-Case Thermal Resistance (q ) .................2C/W Junction-to-Case Thermal Resistance (q ) ...............32C/W JC JC 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. Recommended DC Operating Conditions (T = -40NC to +125NC, unless otherwise noted.) (Notes 2 and 3) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V V 3.0 3.3 3.6 V DD DD DVDD V 3.0 3.3 3.6 V DVDD 0.3 x Input Logic 0 V -0.3 V CS, SDI, SCLK IL V DVDD 0.7 x V DVDD Input Logic 1 V V CS, SDI, SCLK IH V + 0.3 DVDD Analog Voltages (FORCE+,FORCE2, FORCE-, Normal conversion results 0 V V BIAS RTDIN+, RTDIN-) Reference Resistor R 350 10k I REF Cable Resistance R Per lead 0 50 I CABLE Electrical Characteristics (3.0V P V P 3.6V, T = -40NC to +125NC, unless otherwise noted. Typical values are T = +25NC, V = V = 3.3V.) (Notes 2 DD A A DD DVDD and 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS ADC Resolution No missing codes 15 Bits ADC Full-Scale Input Voltage REFIN+ - V (RTDIN+ - RTDIN-) REFIN- Maxim Integrated 2 www.maximintegrated.com