MAX31855

Part: MAX31855 (K, J, N, T, S, R, E versions) — Maxim Integrated

Type: Cold-Junction Compensated Thermocouple-to-Digital Converter

Description: 14-bit, 0.25 °C resolution thermocouple-to-digital converter with cold-junction compensation and a read-only SPI-compatible output, powered from 3.0–3.6 V, with ±2 °C accuracy for K-type from -200 °C to +700 °C.

Operating Conditions:

• Supply voltage: 3.0–3.6 V (3.3 V typical)
• Operating temperature: -40 to +125 °C
• Serial clock frequency: up to 5 MHz
• Thermocouple reading range: -270 °C to +1800 °C (device-level; actual range depends on thermocouple type, see Table 1)

Absolute Maximum Ratings:

• Supply voltage (VCC to GND): -0.3 to +4.0 V
• All other pins: -0.3 V to (VCC + 0.3 V)
• Junction temperature: +150 °C
• Storage temperature: -65 to +150 °C
• Continuous power dissipation (TA = +70 °C, SO): 470.6 mW (derate 5.9 mW/°C above +70 °C)
• ESD (HBM, all pins): ±2 kV
• Lead temperature (soldering, 10 s): +300 °C

Key Specs:

• Supply current (ICC): 900 μA typ, 1500 μA max
• MAX31855K accuracy: ±2 °C (thermocouple -200 to +700 °C, TA -20 to +85 °C); ±4 °C (+700 to +1350 °C); ±6 °C (-270 to +1372 °C, TA -40 to +125 °C)
• Internal cold-junction error: ±2 °C (TA -20 to +85 °C); ±3 °C (TA -40 to +125 °C)
• Thermocouple data resolution: 0.25 °C; cold-junction data resolution: 0.0625 °C
• Conversion time (tCONV): 70 ms typ, 100 ms max
• Power-up conversion time (tCONV_PU): 200 ms min
• Thermocouple input bias current: ±100 nA max
• Logic levels: VIL 0.8 V max, VIH 2.1 V min; VOL 0.4 V max at 1.6 mA; VOH VCC - 0.4 V min at -1.6 mA
• POR threshold: 2 V typ, 2.5 V max

Features:

• Cold-junction compensation
• 14-bit, 0.25 °C resolution
• Versions for K-, J-, N-, T-, S-, R-, and E-type thermocouples
• Simple SPI-compatible read-only interface
• Detects thermocouple shorts to GND or VCC
• Detects open thermocouple

Applications:

• Industrial
• Appliances
• HVAC
• Automotive

Package:

• 8-pin SO (θJA 170 °C/W, θJC 40 °C/W)

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

(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.