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TMP117: TMP117 as Cold junction Temperature Sensor for thermocouple Temperature Measurement

Balaji Appadurai45
Prodigy 200 points
Part Number: TMP117

Hi,

In one of our Temperature Sensor Board, We have chosen P/N#TMP117MAIDRVR. We didn't get the accuracy as as per datasheet (+/-0.3degC). This IC is used for cold Junction reference for Thermocouple Temperature measurement. Thermal Pad is soldered and connected to GND with 2 vias (refer the attached screen shot). Can this impact? TMP117EVM also has the thermal pad connected to GND with 2 vias.

Should we need to make thermal pad as no net and No paste but only Solder mask opening, Will that help in improving accuracy?

What else could impact accuracy? Please suggest if there is any improvement required from design & also from layout point of view?

Schematic:

 

Layout:

Regards,

Balaji Appadurai

  • 0
    TI__Expert 8940 points

    Hi Balaji,

    Thank you for posting to the Sensing forum.

    What is the temperature range where you are seeing the temperature delta? An increase in temperature error has been observed if the thermal pad of the device is soldered, as this can introduce additional stresses and degrade accuracy. Please refer to section 9 of the following Precise Temperature Measurements application report.

    Best regards,

    Nicole