MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter General Description Benefits and Features The MAX31855 performs cold-junction compensation Integration Reduces Design Time and Lowers and digitizes the signal from a K-, J-, N-, T-, S-, R-, or System Cost E-type thermocouple. The data is output in a signed 14-Bit, 0.25C Resolution Converter 14-bit, SPI-compatible, read-only format. This converter Integrated Cold-Junction Compensation resolves temperatures to 0.25C, allows readings as Versions Available for Most Common Thermocouple high as +1800C and as low as -270C, and exhibits Types: K-, J-, N-, T-, S-, R-, and E-Type thermocouple accuracy of 2C for temperatures ranging from -200C to +700C for K-type thermocouples. For full Detects Thermocouple Shorts to GND or V CC range accuracies and other thermocouple types, see the Detects Open Thermocouple Thermal Characteristics specifications. Interfaces to Most Microcontrollers Applications Simple SPI-Compatible Interface (Read-Only) Industrial Appliances Ordering Information appears at end of data sheet. HVAC For related parts and recommended products to use with this part, refer to www.maximintegrated.com/MAX31855.related. Typical Application Circuit V CC 0.1F MAX31855 GND MICROCONTROLLER SO MISO SCK SCK T+ CS SS T- 19-5793 Rev 5 1/15MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Absolute Maximum Ratings Supply Voltage Range (V to GND)...................-0.3V to +4.0V Operating Temperature Range......................... -40C to +125C CC All Other Pins............................................. -0.3V to (V + 0.3V) Junction Temperature......................................................+150C CC Continuous Power Dissipation (T = +70C) Storage Temperature Range ........................... -65C to +150C A SO (derate 5.9mW/C above +70C).......................470.6mW Lead Temperature (soldering, 10s).................................+300C ESD Protection (All Pins, Human Body Model)....................2kV Soldering Temperature (reflow) ......................................+260C 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. (Note 1) Package Thermal Characteristics SO Junction-to-Ambient Thermal Resistance ( ) ........170C/W JA Junction-to-Case Thermal Resistance ( ) ...............40C/W 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 Operating Conditions (T = -40C to +125C, unless otherwise noted.) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Power-Supply Voltage V (Note 2) 3.0 3.3 3.6 V CC Input Logic 0 V -0.3 +0.8 V IL V + CC Input Logic 1 V 2.1 V IH 0.3 DC Electrical Characteristics (3.0V V P 3.6V, T = -40C to +125C, unless otherwise noted.) CC A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Power-Supply Current I 900 1500 A CC T = -40C to +125C, 100mV across the A Thermocouple Input Bias Current -100 +100 nA thermocouple inputs Power-Supply Rejection -0.3 C/V Power-On Reset Voltage V (Note 3) 2 2.5 V POR Threshold Power-On Reset Voltage 0.2 V Hysteresis V - CC Output High Voltage V I = -1.6mA V OH OUT 0.4 Output Low Voltage V I = 1.6mA 0.4 V OL OUT Maxim Integrated 2 www.maximintegrated.com