19-5793; Rev 2; 2/12 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter General Description The MAX31855 performs cold-junction compensation and digitizes the signal from a K-, J-, N-, T-, S-, R-, or E-type thermocouple. The data is output in a signed 14-bit, SPI-compatible, read-only format. This converter resolves temperatures to 0.25NC, allows readings as high as +1800NC and as low as -270NC, and exhibits thermocouple accuracy of ±2NC for temperatures ranging from -200NC to +700NC for K-type thermocouples. For full range accuracies and other thermocouple types, see the Thermal Characteristics specifications. Applications Features S Cold-Junction Compensation S 14-Bit, 0.25NC Resolution S Versions Available for K-, J-, N-, T-, S-, R-, and E-Type Thermocouples (see Table 1) S Simple SPI-Compatible Interface (Read-Only) S Detects Thermocouple Shorts to GND or VCC S Detects Open Thermocouple Ordering Information appears at end of data sheet. Industrial Appliances For related parts and recommended products to use with this part, refer to: www.maxim-ic.com/MAX31855.related HVAC Automotive Typical Application Circuit VCC 0.1µF MAX31855 GND MICROCONTROLLER SO MISO T+ SCK SCK T- CS SS ����������������������������������������������������������������� Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter ABSOLUTE MAXIMUM RATINGS Supply Voltage Range (VCC to GND)...................-0.3V to +4.0V All Other Pins............................................. -0.3V to (VCC + 0.3V) Continuous Power Dissipation (TA = +70NC) SO (derate 5.9mW/NC above +70NC)........................470.6mW ESD Protection (All Pins, Human Body Model)....................±2kV Operating Temperature Range......................... -40NC to +125NC Junction Temperature......................................................+150NC Storage Temperature Range ........................... -65NC to +150NC Lead Temperature (soldering, 10s).................................+300NC 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 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) SO Junction-to-Ambient Thermal Resistance (BJA).........170NC/W Junction-to-Case Thermal Resistance (BJC)................40NC/W Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. RECOMMENDED OPERATING CONDITIONS (TA = -40NC to +125NC, unless otherwise noted.) PARAMETER SYMBOL Power-Supply Voltage VCC Input Logic 0 VIL Input Logic 1 VIH CONDITIONS (Note 2) MIN TYP MAX UNITS 3.0 3.3 3.6 V -0.3 +0.8 V 2.1 VCC + 0.3 V TYP MAX UNITS 900 1500 FA +100 nA DC ELECTRICAL CHARACTERISTICS (3.0V P VCC P 3.6V, TA = -40NC to +125NC, unless otherwise noted.) PARAMETER Power-Supply Current SYMBOL CONDITIONS MIN ICC TA = -40NC to +125NC, 100mV across the thermocouple inputs Thermocouple Input Bias Current -100 Power-Supply Rejection Power-On Reset Voltage Threshold -0.3 VPOR (Note 3) 2 Power-On Reset Voltage Hysteresis NC/V 2.5 0.2 Output High Voltage VOH IOUT = -1.6mA Output Low Voltage VOL IOUT = 1.6mA V V VCC 0.4 V 0.4 V ����������������������������������������������������������������� Maxim Integrated Products 2 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter THERMAL CHARACTERISTICS (3.0V P VCC P 3.6V, TA = -40NC to +125NC, unless otherwise noted.) (Note 4) PARAMETER MAX31855K Thermocouple Temperature Gain and Offset Error (41.276FV/NC nominal sensitivity) (Note 4) MAX31855J Thermocouple Temperature Gain and Offset Error (57.953FV/NC nominal sensitivity) (Note 4) MAX31855N Thermocouple Temperature Gain and Offset Error (36.256FV/NC nominal sensitivity) (Note 4) MAX31855T Thermocouple Temperature Gain and Offset Error (52.18FV/NC nominal sensitivity) (Note 4) MAX31855E Thermocouple Temperature Gain and Offset Error (76.373FV/NC nominal sensitivity) (Note 4) MAX31855R Thermocouple Temperature Gain and Offset Error (10.506FV/NC nominal sensitivity) (Note 4) MAX31855S Thermocouple Temperature Gain and Offset Error (9.587FV/NC nominal sensitivity) (Note 4) SYMBOL CONDITIONS MIN TYP MAX TTHERMOCOUPLE = -200NC to +700NC, TA = -20NC to +85NC (Note 3) -2 +2 TTHERMOCOUPLE = +700NC to +1350NC, TA = -20NC to +85NC (Note 3) -4 +4 TTHERMOCOUPLE = -270NC to +1372NC, TA = -40NC to +125NC (Note 3) -6 +6 TTHERMOCOUPLE = -210NC to +750NC, TA = -20NC to +85NC (Note 3) -2 +2 TTHERMOCOUPLE = -210NC to +1200NC, TA = -40NC to +125NC (Note 3) -4 +4 TTHERMOCOUPLE = -200NC to +700NC, TA = -20NC to +85NC (Note 3) -2 +2 TTHERMOCOUPLE = +700NC to +1300NC, TA = -20NC to +85NC (Note 3) -4 +4 TTHERMOCOUPLE = -270NC to +1300NC, TA = -40NC to +125NC (Note 3) -6 +6 TTHERMOCOUPLE = -270NC to +400NC, TA = -20NC to +85NC (Note 3) -2 +2 TTHERMOCOUPLE = -270NC to +400NC, TA = -40NC to +125NC (Note 3) -4 +4 TTHERMOCOUPLE = -200NC to +700NC, TA = -20NC to +85NC (Note 3) -2 +2 TTHERMOCOUPLE = +700NC to +1000NC, TA = -20NC to +85NC (Note 3) -3 +3 TTHERMOCOUPLE = -270NC to +1000NC, TA = -40NC to +125NC (Note 3) -5 +5 TTHERMOCOUPLE = -50NC to +700NC, TA = -20NC to +85NC (Note 3) -2 +2 TTHERMOCOUPLE = +700NC to +1768NC, TA = -20NC to +85NC (Note 3) -4 +4 TTHERMOCOUPLE = -50NC to +1768NC, TA = -40NC to +125NC (Note 3) -6 +6 TTHERMOCOUPLE = -50NC to +700NC, TA = -20NC to +85NC (Note 3) -2 +2 TTHERMOCOUPLE = +700NC to +1768NC, TA = -20NC to +85NC (Note 3) -4 +4 TTHERMOCOUPLE = -50NC to +1768NC, TA = -40NC to +125NC (Note 3) -6 +6 UNITS NC NC NC NC NC NC NC ����������������������������������������������������������������� Maxim Integrated Products 3 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter THERMAL CHARACTERISTICS (continued) (3.0V P VCC P 3.6V, TA = -40NC to +125NC, unless otherwise noted.) (Note 4) PARAMETER SYMBOL CONDITIONS MIN Thermocouple Temperature Data Resolution Cold-Junction Temperature Data Resolution Thermocouple Conversion Power-Up Time MAX 0.25 Internal Cold-Junction Temperature Error Temperature Conversion Time (Thermocouple, Cold Junction, Fault Detection) TYP NC TA = -20NC to +85NC (Note 3) -2 +2 TA = -40NC to +125NC (Note 3) -3 +3 0.0625 TA = -40NC to +125NC tCONV (Note 5) tCONV_PU (Note 6) 70 UNITS NC NC 100 200 ms ms SERIAL-INTERFACE TIMING CHARACTERISTICS (See Figure 1 and Figure 2.) PARAMETER Input Leakage Current SYMBOL ILEAK CONDITIONS (Note 7) MIN Input Capacitance CIN Serial-Clock Frequency fSCL SCK Pulse-High Width tCH 100 SCK Pulse-Low Width tCL 100 MAX UNITS +1 µA 8 pF 5 SCK Rise and Fall Time CS Fall to SCK Rise TYP -1 ns ns 200 tCSS 100 ns ns 100 SCK to CS Hold MHz ns CS Fall to Output Enable tDV 100 ns CS Rise to Output Disable SCK Fall to Output Data Valid tTR 40 ns 40 ns CS Inactive Time tDO (Note 3) 200 ns All voltages are referenced to GND. Currents entering the IC are specified positive, and currents exiting the IC are negative. Guaranteed by design; not production tested. Not including cold-junction temperature error or thermocouple nonlinearity. Specification is 100% tested at TA = +25NC. Specification limits over temperature (TA = TMIN to TMAX) are guaranteed by design and characterization; not production tested. Note 6: Because the thermocouple temperature conversions begin at VPOR, depending on VCC slew rates, the first thermocouple temperature conversion may not produce an accurate result. Therefore, the tCONV_PU specification is required after VCC is greater than VCCMIN to guarantee a valid thermocouple temperature conversion result. Note 7: For all pins except T+ and T- (see the Thermocouple Input Bias Current parameter in the DC Electrical Characteristics table). Note 2: Note 3: Note 4: Note 5: ����������������������������������������������������������������� Maxim Integrated Products 4 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Serial-Interface Diagrams CS SCK SO D31 D8 D7 D6 D5 D4 D2 D3 D1 D0 Figure 1. Serial-Interface Protocol tCSS CS tCH tCL SCK tDV tDO tTR SO D31 D3 D2 D1 D0 Figure 2. Serial-Interface Timing ����������������������������������������������������������������� Maxim Integrated Products 5 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Typical Operating Characteristics (VCC = +3.3V, TA = +25NC, unless otherwise noted.) 1.0 VCC = 3.3V 0.8 VCC = 3.0V 0.6 0.4 0.7 0.2 0.5 0.4 NOTE: THIS DATA WAS TAKEN IN PRECISION BATH SO HIGH TEMPERATURE LIMIT IS 90°C 0.3 0.2 0.1 0 -0.1 0 -40 -20 0 20 40 60 80 -0.2 100 120 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) ADC ACCURACY vs. ADC INPUT VOLTAGE ACROSS TEMPERATURE ADC ACCURACY vs. ADC INPUT VOLTAGE ACROSS VCC 0.1 AT +85°C -0.2 -0.3 -0.4 AT +25°C -0.5 VCC = 3.0V -0.1 -0.2 ADC ACCURACY (°C) 0 -0.1 0 MAX31855 toc03 AT -40°C 0.2 MAX31855 toc04 TEMPERATURE (°C) 0.3 ADC ACCURACY (°C) VCC = 3.3V 0.6 MEASUREMENT ERROR (°C) VCC = 3.6V 1.2 SUPPLY CURRENT (mA) MAX31855 toc01 1.4 MAX31855 toc02 INTERNAL TEMPERATURE SENSOR ACCURACY SUPPLY CURRENT vs. TEMPERATURE -0.3 VCC = 3.3V -0.4 -0.5 -0.6 VCC = 3.6V -0.7 -0.8 -0.6 -0.9 VCC = 3.3V -0.7 0 INTERNAL TEMPERATURE = +25°C -1.0 20 40 ADC INPUT VOLTAGE (mV) 60 0 20 40 60 ADC INPUT VOLTAGE (mV) ����������������������������������������������������������������� Maxim Integrated Products 6 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Pin Description Pin Configuration TOP VIEW T- 2 T+ MAX31855 3 1 GND FUNCTION Ground 2 T- 8 DNC 3 T+ Thermocouple Input. See Table 1. 7 SO 4 VCC Power-Supply Voltage 5 SCK Serial-Clock Input 6 CS Active-Low Chip Select. Set CS low to enable the serial interface. 7 SO Serial-Data Output 8 DNC 6 VCC 4 NAME Thermocouple Input. See Table 1. Do not connect to GND. + GND 1 PIN CS 5 SCK SO Do Not Connect Block Diagram VCC MAX31855 COLD-JUNCTION COMPENSATION T+ S5 DIGITAL CONTROL VCC SCK SO CS S4 ADC TS1 S2 FAULT DETECTION GND S3 REFERENCE VOLTAGE ����������������������������������������������������������������� Maxim Integrated Products 7 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Detailed Description The MAX31855 is a sophisticated thermocouple-todigital converter with a built-in 14-bit analog-to-digital converter (ADC). The device also contains cold-junction compensation sensing and correction, a digital controller, an SPI-compatible interface, and associated control logic. The device is designed to work in conjunction with an external microcontroller (FC) in thermostatic, process-control, or monitoring applications. The device is available in several versions, each optimized and trimmed for a specific thermocouple type (K, J, N, T, S, R, or E.). The thermocouple type is indicated in the suffix of the part number (e.g., MAX31855K). See the Ordering Information table for all options. Temperature Conversion The device includes signal-conditioning hardware to convert the thermocouple’s signal into a voltage compatible with the input channels of the ADC. The T+ and T- inputs connect to internal circuitry that reduces the introduction of noise errors from the thermocouple wires. Before converting the thermoelectric voltages into equivalent temperature values, it is necessary to compensate for the difference between the thermocouple coldjunction side (device ambient temperature) and a 0NC virtual reference. For a K-type thermocouple, the voltage changes by about 41FV/NC, which approximates the thermocouple characteristic with the following linear equation: VOUT = (41.276FV/NC) x (TR - TAMB) where VOUT is the thermocouple output voltage (FV), TR is the temperature of the remote thermocouple junction (NC), and TAMB is the temperature of the device (NC). Other thermocouple types use a similar straight-line approximation but with different gain terms. Note that the MAX31855 assumes a linear relationship between temperature and voltage. Because all thermocouples exhibit some level of nonlinearity, apply appropriate correction to the device’s output data. Cold-Junction Compensation The function of the thermocouple is to sense a difference in temperature between two ends of the thermocouple wires. The thermocouple’s “hot” junction can be read across the operating temperature range (Table 1). The reference junction, or “cold” end (which should be at Table 1. Thermocouple Wire Connections and Nominal Sensitivities TYPE T- WIRE T+ WIRE TEMP RANGE (°C) SENSITIVITY (µV/°C) COLD-JUNCTION SENSITIVITY (µV/°C) (0NC TO +70NC) K Alumel Chromel -270 to +1372 41.276 (0NC to +1000NC) 40.73 J Constantan Iron -210 to +1200 57.953 (0NC to +750NC) 52.136 N Nisil Nicrosil -270 to + 1300 36.256 (0NC to +1000NC) 27.171 S Platinum Platinum/Rhodium +50 to +1768 9.587 (0NC to +1000NC) 6.181 T Constantan Copper -270 to +400 52.18 (0NC to +400NC) 41.56 E Constantan Chromel -270 to +1000 76.373 (0NC to +1000NC) 44.123 R Platinum Platinum/Rhodium -50 to +1768 10.506 (0NC to +1000NC) 6.158 ����������������������������������������������������������������� Maxim Integrated Products 8 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter the same temperature as the board on which the device is mounted) can range from -55NC to +125NC. While the temperature at the cold end fluctuates, the device continues to accurately sense the temperature difference at the opposite end. The device senses and corrects for the changes in the reference junction temperature with cold-junction compensation. It does this by first measuring its internal die temperature, which should be held at the same temperature as the reference junction. It then measures the voltage from the thermocouple’s output at the reference junction and converts this to the noncompensated thermocouple temperature value. This value is then added to the device’s die temperature to calculate the thermocouple’s “hot junction” temperature. Note that the “hot junction” temperature can be lower than the cold junction (or reference junction) temperature. Optimal performance from the device is achieved when the thermocouple cold junction and the device are at the same temperature. Avoid placing heat-generating devices or components near the MAX31855 because this could produce cold-junction-related errors. Conversion Functions During the conversion time, tCONV, three functions are performed: the temperature conversion of the internal cold-junction temperature, the temperature conversion of the external thermocouple, and the detection of thermocouple faults. When executing the temperature conversion for the internal cold-junction compensation circuit, the connection to signal from the external thermocouple is opened (switch S4) and the connection to the cold-junction compensation circuit is closed (switch S5). The internal T- reference to ground is still maintained (switch S3 is closed) and the connections to the fault-detection circuit are open (switches S1 and S2). When executing the temperature conversion of the external thermocouple, the connections to the internal fault-detection circuit are opened (switches S1 and S2 in the Block Diagram) and the switch connecting the coldjunction compensation circuit is opened (switch S5). The internal ground reference connection (switch S3) and the connection to the ADC (switch S4) are closed. This allows the ADC to process the voltage detected across the T+ and T- terminals. During fault detection, the connections from the external thermocouple and cold-junction compensation circuit to the ADC are opened (switches S4 and S5). The internal ground reference on T- is also opened (switch S3). The connections to the internal fault-detection circuit are closed (switch S1 and S2). The fault-detection circuit tests for shorted connections to VCC or GND on the T+ and T- inputs, as well as looking for an open thermocouple condition. Bits D0, D1, and D2 of the output data are normally low. Bit D2 goes high to indicate a thermocouple short to VCC, bit D1 goes high to indicate a thermocouple short to GND, and bit D0 goes high to indicate a thermocouple open circuit. If any of these conditions exists, bit D16 of the SO output data, which is normally low, also goes high to indicate that a fault has occurred. Serial Interface The Typical Application Circuit shows the device interfaced with a microcontroller. In this example, the device processes the reading from the thermocouple and transmits the data through a serial interface. Drive CS low and apply a clock signal at SCK to read the results at SO. Conversions are always being performed in the background. The fault and temperature data are only be updated when CS is high. Drive CS low to output the first bit on the SO pin. A complete serial-interface read of the cold-junction compensated thermocouple temperature requires 14 clock cycles. Thirty-two clock cycles are required to read both the thermocouple and reference junction temperatures (Table 2 and Table 3.) The first bit, D31, is the thermocouple temperature sign bit, and is presented to the SO pin within tDV of the falling edge of CS. Bits D[30:18] contain the converted temperature in the order of MSB to LSB, and are presented to the SO pin within tD0 of the falling edge of SCK. Bit D16 is normally low and goes high when the thermocouple input is open or shorted to GND or VCC. The reference junction temperature data begins with D15. CS can be taken high at any point while clocking out conversion data. If T+ and T- are unconnected, the thermocouple temperature sign bit (D31) is 0, and the remainder of the thermocouple temperature value (D[30:18]) is 1. Figure 1 and Figure 2 show the serial-interface timing and order. Table 2 and Table 3 show the SO output bit weights and functions. ����������������������������������������������������������������� Maxim Integrated Products 9 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Table 2. Memory Map—Bit Weights and Functions 14-BIT THERMOCOUPLE RES TEMPERATURE DATA D31 BIT VALUE D30 Sign … MSB 210 (1024NC) … D18 LSB 2-2 (0.25NC) D17 Reserved FAULT 12-BIT INTERNAL TEMPERATURE BIT DATA D16 1= Fault D15 D14 … MSB 26 Sign … (64NC) D4 LSB 2-4 (0.0625NC) RES D3 Reserved SCV SCG OC BIT BIT BIT D2 D1 D0 1= 1= Short Short to to VCC GND 1= Open Circuit Table 3. Memory Map—Descriptions BIT NAME DESCRIPTION D[31:18] 14-Bit Thermocouple Temperature Data D17 Reserved D16 Fault D[15:4] 12-Bit Internal Temperature Data These bits contain the signed 14-bit thermocouple temperature value. See Table 4. This bit always reads 0. This bit reads at 1 when any of the SCV, SCG, or OC faults are active. Default value is 0. These bits contain the signed 12-bit value of the reference junction temperature. See Table 5. D3 Reserved This bit always reads 0. D2 SCV Fault D1 SCG Fault This bit is a 1 when the thermocouple is short-circuited to VCC. Default value is 0. This bit is a 1 when the thermocouple is short-circuited to GND. Default value is 0. D0 OC Fault This bit is a 1 when the thermocouple is open (no connections). Default value is 0. Table 4. Thermocouple Temperature Data Format Table 5. Reference Junction Temperature Data Format TEMPERATURE (NC) DIGITAL OUTPUT (D[31:18]) TEMPERATURE (NC) DIGITAL OUTPUT (D[15:4]) +1600.00 0110 0100 0000 00 +127.0000 0111 1111 0000 +1000.00 0011 1110 1000 00 +100.5625 0110 0100 1001 +100.75 0000 0110 0100 11 +25.0000 0001 1001 0000 +25.00 0000 0001 1001 00 0.0000 0000 0000 0000 0.00 0000 0000 0000 00 -0.0625 1111 1111 1111 -0.25 1111 1111 1111 11 -1.0000 1111 1111 0000 -1.00 1111 1111 1111 00 -20.0000 1110 1100 0000 -250.00 1111 0000 0110 00 -55.0000 1100 1001 0000 Note: The practical temperature ranges vary with the thermocouple type. ���������������������������������������������������������������� Maxim Integrated Products 10 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Applications Information The thermocouple system’s accuracy can also be improved by following these precautions: Noise Considerations • Use the largest wire possible that does not shunt heat away from the measurement area. Because of the small signal levels involved, thermocouple temperature measurement is susceptible to powersupply coupled noise. The effects of power-supply noise can be minimized by placing a 0.1FF ceramic bypass capacitor close to the VCC pin of the device and to GND. The input amplifier is a low-noise amplifier designed to enable high-precision input sensing. Keep the thermocouple and connecting wires away from electrical noise sources. It is strongly recommended to add a 10nF ceramic surface-mount differential capacitor, placed across the T+ and T- pins, in order to filter noise on the thermocouple lines. Thermal Considerations Self-heating degrades the device’s temperature measurement accuracy in some applications. The magnitude of the temperature errors depends on the thermal conductivity of the device package, the mounting technique, and the effects of airflow. Use a large ground plane to improve the device’s temperature measurement accuracy. • If a small wire is required, use it only in the region of the measurement, and use extension wire for the region with no temperature gradient. • Avoid mechanical stress and vibration, which could strain the wires. • When using long thermocouple wires, use a twisted pair extension wire. • Avoid steep temperature gradients. • Try to use the thermocouple wire well within its temperature rating. • Use the proper sheathing material in hostile environments to protect the thermocouple wire. • Use extension wire only at low temperatures and only in regions of small gradients. • Keep an event log and a continuous record of thermocouple resistance. ���������������������������������������������������������������� Maxim Integrated Products 11 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Ordering Information PART THERMOCOUPLE TYPE MEASURED TEMP RANGE PIN-PACKAGE MAX31855KASA+ K -200NC to +1350NC 8 SO MAX31855KASA+T K -200NC to +1350NC 8 SO MAX31855JASA+ J -40NC to +750NC 8 SO MAX31855JASA+T J -40NC to +750NC 8 SO MAX31855NASA+ N -200NC to + 1300NC 8 SO MAX31855NASA+T N -200NC to + 1300NC 8 SO MAX31855SASA+ S +50NC to +1600NC 8 SO MAX31855SASA+T S +50NC to +1600NC 8 SO MAX31855TASA+ T -250NC to +400NC 8 SO MAX31855TASA+T T -250NC to +400NC 8 SO MAX31855EASA+ E -40NC to +900NC 8 SO MAX31855EASA+T E -40NC to +900NC 8 SO MAX31855RASA+ R -50NC to +1770NC 8 SO MAX31855RASA+T R -50NC to +1770NC 8 SO Note: All devices are specified over the -40°C to +125°C operating temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. Package Information For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 8 SO S8+4 21-0041 90-0096 ���������������������������������������������������������������� Maxim Integrated Products 12 MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter Revision History REVISION NUMBER REVISION DATE DESCRIPTION 0 3/11 Initial release 1 11/11 Corrected ESD protection value; added “S” and “R” type specifications 2/12 Corrected the thermocouple temperature conditions in the Thermal Characteristics table and Table 1; added clarification to the Serial Interface section to help users better understand how to communicate with the device; added a recommendation to add a 10nF differential capacitor to the T+/T- pins in the Noise Considerations section 2 PAGES CHANGED — 1, 2, 3, 8, 12 3, 8, 9, 11 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2012 Maxim Integrated Products 13 Maxim is a registered trademark of Maxim Integrated Products, Inc.