Part: MAX31855 — Maxim Integrated Type: Thermocouple-to-Digital Converter Description: The MAX31855 performs cold-junction compensation and digitizes the signal from K-, J-, N-, T-, S-, R-, or E-type thermocouples, outputting signed 14-bit, SPI-compatible data with 0.25 °C resolution and a temperature range of -270 °C to +1800 °C.

Operating Conditions:

• Supply voltage: 3.0–3.6 V
• Operating temperature: -40 to +125 °C

Absolute Maximum Ratings:

• Max supply voltage: +4.0 V
• Max junction temperature: +150 °C
• Max storage temperature: +150 °C

Key Specs:

• Thermocouple temperature resolution: 0.25 °C
• K-type thermocouple accuracy: ±2 °C (T_THERMOCOUPLE = -200 °C to +700 °C, T_A = -20 °C to +85 °C)
• Internal cold-junction temperature error: ±2 °C (T_A = -20 °C to +85 °C)
• Cold-junction temperature data resolution: 0.0625 °C
• Power-supply current: 900 μA (typ), 1500 μA (max)
• Thermocouple input bias current: -100 nA to 100 nA (T_A = -40 °C to +125 °C)
• Temperature conversion time: 70 ms (typ), 100 ms (max)
• Serial-clock frequency: 5 MHz (max)

Features:

• Cold-Junction Compensation
• 14-Bit, 0.25 °C Resolution
• Versions available for K-, J-, N-, T-, S-, R-, and E-Type Thermocouples
• Simple SPI-Compatible Interface (Read-Only)
• Detects Thermocouple Shorts to GND or VCC
• Detects Open Thermocouple

Applications:

• Industrial
• Appliances
• HVAC
• Automotive

Package:

• SO

Features

• S Cold-Junction Compensation
• S 14-Bit, 0.25 N C 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.

For related parts and recommended products to use with this part, refer to: www.maxim-ic.com/MAX31855.related

MAX31855 – 8-pin SO Package

Notes

• The MAX31855 is a thermocouple-to-digital converter with integrated cold-junction compensation.
• T− and T+ form the thermocouple input pair; polarity must be observed.
• SCK, CS, and SO implement a standard SPI interface for reading temperature data.
• ONC (Open Circuit) output indicates an open thermocouple condition.

(3.0V P VCC P 3.6V, TA = -40 N C to +125 N C, unless otherwise noted.)

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.

(TA = -40 N C to +125 N C, unless otherwise noted.)

SO

Junction-to-Ambient Thermal Resistance ( B JA) ........170 N C/W Junction-to-Case Thermal Resistance ( B JC) ...............40 N C/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 .

Pin Configurations appear at end of data sheet.

Functional Diagrams continued at end of data sheet.

UCSP is a trademark of Maxim Integrated Products, Inc.

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.