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LDC1312EVM: external 40-MHz oscillator

K.Yaita
Guru 29690 points
Part Number: LDC1312EVM

Hi Team,

There is external 40-MHz oscillator on LDC1312EVM.
Should we divide more than 2 if using single channel operation because of the following Table 1?


I would like to ask what is concern if we use fREFx=40MHz when single channel operation.

Best Regards,
Yaita / Japan disty

  • 0
    TI__Genius 13335 points
    Hello Yaita-san,
    If using a single channel measurement, then yes the reference frequency should be divided. However, if you are using both channels then you can safely operate at 40MHz.
    Regards,
    Luke
  • 0 in reply to Luke LaPointe
    Guru 29690 points

    Hi Luke-san,

    Thank you always for your support.

    >However, if you are using both channels then you can safely operate at 40MHz.
    Should I set external coil and capacitor at unused channel that is just enabled for 40MHz operation?

    I saw the following application note and it seems external coil and capacitor are required but would like to confirm just in case.
    -----------------------------------------------------------------
    (page 5)
    If the Channel 0 activation time (which is roughly Q/fSENSOR) is short enough, it may be advantageous to
    attach an additional sensor onto channel 1 but ignore the conversion data from Channel 1. In this way the
    LDC131x can operate with fREF=40 MHz, but at the cost of conversion time on the second channel. The
    sensor geometries do not need to match Channel 0’s sensor.
    http://www.tij.co.jp/jp/lit/an/snoa945/snoa945.pdf
    -----------------------------------------------------------------

    Best Regards,
    Yaita / Japan disty

  • 0 in reply to K.Yaita
    TI__Genius 13335 points
    Hello Yaita-san,
    Yes, the unused channel should still have a valid sensor connected to it. You can set the conversion time to the minimum and ignore its data.
    Regards,
    Luke
  • 0 in reply to Luke LaPointe
    Guru 29690 points

    Hi Luke-san,

    Thank you for your reply.
    Could you tell me the background why valid sensor(LC tank) required although it is unused?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 13335 points
    Hi Yaita-san,
    The issue you will run into is that with no sensor connected you will get error flags like the Watchdog Timeout Error. I believe that is the only issue though.
    Regards,
    Luke