19-5793 Rev 2 2/12 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter General Description Features The MAX31855 performs cold-junction compensation S Cold-Junction Compensation and digitizes the signal from a K-, J-, N-, T-, S-, R-, or S 14-Bit, 0.25NC Resolution E-type thermocouple. The data is output in a signed S Versions Available for K-, J-, N-, T-, S-, R-, and 14-bit, SPI-compatible, read-only format. This converter E-Type Thermocouples (see Table 1) resolves temperatures to 0.25NC, allows readings as high as +1800NC and as low as -270NC, and exhibits thermo- S Simple SPI-Compatible Interface (Read-Only) couple accuracy of 2NC for temperatures ranging from S Detects Thermocouple Shorts to GND or V CC -200NC to +700NC for K-type thermocouples. For full S Detects Open Thermocouple range accuracies and other thermocouple types, see the Thermal Characteristics specifications. Ordering Information appears at end of data sheet. Applications Industrial For related parts and recommended products to use with this part, Appliances refer to: www.maxim-ic.com/MAX31855.related HVAC Automotive Typical Application Circuit V CC 0.1F MAX31855 GND MICROCONTROLLER SO MISO T+ SCK SCK CS SS T- Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter ABSOLUTE MAXIMUM RATINGS Supply Voltage Range (V to GND) ..................-0.3V to +4.0V Operating Temperature Range ........................ -40NC to +125NC CC All Other Pins ............................................ -0.3V to (V + 0.3V) Junction Temperature .....................................................+150NC CC Continuous Power Dissipation (T = +70NC) Storage Temperature Range .......................... -65NC to +150NC A SO (derate 5.9mW/NC above +70NC) .......................470.6mW Lead Temperature (soldering, 10s) ................................+300NC ESD Protection (All Pins, Human Body Model) ...................2kV Soldering Temperature (reflow) .....................................+260NC Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional opera- tion 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) SO Junction-to-Ambient Thermal Resistance (B ) ........170NC/W JA Junction-to-Case Thermal Resistance (B ) ...............40NC/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.maxim-ic.com/thermal-tutorial. RECOMMENDED OPERATING CONDITIONS (T = -40NC to +125NC, 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 P V P 3.6V, T = -40NC to +125NC, unless otherwise noted.) CC A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Power-Supply Current I 900 1500 FA CC T = -40NC to +125NC, 100mV across the A Thermocouple Input Bias Current -100 +100 nA thermocouple inputs Power-Supply Rejection -0.3 NC/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 Products 2