MAX6675

Part: MAX6675, Maxim Integrated

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

Description: The MAX6675 is a cold-junction compensated K-thermocouple-to-digital converter with 12-bit, 0.25°C resolution, capable of reading temperatures up to +1024°C, and featuring a simple SPI-compatible serial interface.

Operating Conditions:

• Supply voltage: +3.0V to +5.5V
• Operating temperature: -20°C to +85°C
• Thermocouple temperature range: 0°C to +1024°C
• Resolution: 0.25°C

Absolute Maximum Ratings:

• Max supply voltage: +6V (VCC to GND)
• Max continuous current: 50mA (SO Current)
• Max junction/storage temperature: +150°C (Junction Temperature)

Key Specs:

• Temperature Error: ±8 LSB (T_THERMOCOUPLE = 0°C to +700°C, T_A = +25°C, V_CC = +3.3V)
• Cold-Junction Compensation Error: ±3.0 °C (T_A = -20°C to V_CC = +3.3V)
• Resolution: 0.25 °C
• Supply Voltage: +3.0V to +5.5V
• Supply Current: 1.5 mA (Max)
• Serial Clock Frequency: 4.3 MHz (Max)
• Conversion Time: 0.22 mV s (Max)

Features:

• Direct Digital Conversion of Type-K Thermocouple Output
• Cold-Junction Compensation
• Simple SPI-Compatible Serial Interface
• 12-Bit, 0.25°C Resolution
• Open Thermocouple Detection

Applications:

• Industrial
• Appliances
• HVAC

Package:

• 8 SO

• Direct Digital Conversion of Type -K Thermocouple Output
• Cold-Junction Compensation
• Simple SPI-Compatible Serial Interface
• 12-Bit, 0.25°C Resolution
• Open Thermocouple Detection

(V CC = +3.0V to +5.5V, T A = -20°C to +85°C, unless otherwise noted. Typical values specified at +25°C.) (Note 1)

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• SO, SCK, CS , T-, T+ to GND .....................-0.3V to V CC + 0.3V
• SO Current ....................................................................... 50mA
• ESD Protection (Human Body Model) .......................... ±2000V
• Continuous Power Dissipation (T A = +70°C) 8-Pin SO (derate 5.88mW/°C above +70°C) ............. 471mW
• Operating Temperature Range .......................... -20°C to +85°C

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.

Self-heating degrades the temperature measurement accuracy of the MAX6675 in some applications. The magnitude of the temperature errors depends on the thermal conductivity of the MAX6675 package, the mounting technique, and the effects of airflow. Use a large ground plane to improve the temperature measurement accuracy of the MAX6675.

The accuracy of a thermocouple system can also be improved by following these precautions:

• Use the largest wire possible that does not shunt heat away from the measurement area.
• If 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 twistedpair 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.

For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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.

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