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TMP63: TMP6331DYAR

Kent Liew
Intellectual 325 points
Part Number: TMP63

Tool/software:

Hi,

Good day.

Customer feedback that that they found 1pc of received parts (PN#TMP6331DYAR) is with low resistance value (2.45Kohm) issue.

They have done measured the resistance value using an LCR meter at room temperature (~25 °C). Also, understand that the TMP6331DYAR is specified at 100 kΩ nominal resistance at 25 °C with ±1% tolerance, and that as a PTC thermistor, its resistance should increase at higher temperatures and decrease at lower temperatures. Given this, the measured value of 2.45 kohm appears to deviate significantly from the expected specification.

Kindly advise if there are any special measurement conditions (e.g., bias voltage, test frequency, specific setup requirements) that should be applied to obtain the correct resistance value?

Could you please help to review and advise?

Thanks.

Regards,

Kent

  • 0
    TI__Genius 12375 points

    Hi Kent,

    The key point to understand when using the TMP6x devices is that they are active silicon devices, not passives like NTCs. Hence, their resistance cannot be measured directly with an LCR meter.

    First, the TMP63 must be properly biased either with a current source or a bias resistor, like so:

    For TMP63, the bias resistor should be 100Kohm. You are correct that at 25C the TMP63 should be about 100Kohms. This means the voltage across the TMP63 at 25C should be half of Vbias. 

    To get the resistance, the customer must measure the voltage across the TMP63, and calculate the resistance based on the current flowing through both Rbias and the TMP63.

    Please advise the customer to use a 100Kohm bias resistor if they are not already doing so, and to measure the voltage across the PTC and then calculate resistance. They should get the correct resistance value after doing that.

    Regards

    -Alex Thompson