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LDC1612: Temperature Drift

Takashi Onawa
Genius 13200 points
Part Number: LDC1612

Hi Team,

My customer has tested temperature drift trend of LDC1612 resonant frequency using our EVM with their original coil. The resonant frequency tends to be  slightly increased until 60C but it became suddenly down trend over 60C as follows(highlighted red circle). 

Do you have any good idea to explain why it became down trend over 60C condition?
I pointed out strap capacitor's temperature characteristics but they've already change them to CH grade so capacitance should be stable though the tested temperature range.
 

Clock : External Oscillator(40MHz)

Capacitance ：120[pF] , CH Grade

Current setting：15 (0~31)

Sensor：LDC Reference Coil (M) on EVM

Regards,

Takashi Onawa

  • 0
    TI__Expert 8900 points

    Hi Onawa-san,

    Thank you for posting.

    Can you please provide further details on the test setup? For example, was there a target during this test and if so, what was the distance from the sensor to the target? 

    Best regards,

    Nicole

  • 0 in reply to Nicole Khoury
    TI__Genius 13200 points

    Hi Nicole-san,

    Thank you for your prompt response on this.

    The data was took under no target condition(there is no metal around the sensor) in order to measure the offset value of resonance frequency.

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Expert 8900 points

    Hi Onawa-san,

    If C0G capacitors are being used they should be stable across temperature, with a 30 ppm/ºC temperature coefficient. The temperature rise in the copper of the coil will increase the series resistance, and it is possible that this is event is a result of variation in inductance or other components on the EVM. 

    Is it possible to observe the frequency behavior across a higher temperature range, in order to see the behavior across 60ºC before deceasing the temperature? Additionally, if possible it may be helpful to have further information regarding the test setup and the EVM in the temperature chamber.

    Best regards,

    Nicole