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crystal LDC1000

Carlos Scorzato
Prodigy 30 points

Hi Team
I use LDC100 IC, and connected 8MHz crystal, between 14 and 15 pins. With capacitor 20pF in both pins to ground.
I adjusted PWR register to active (0x01) and CLK selected register (0x02) xtal selected and enable.
But don't have any signal over crystal pins.
Could you help me.

Carlos

  • 0
    TI__Genius 14270 points

    Hello Carlos,

    Please use the capacitor value for crystal recommended by the crystal manufacturer if a value other than 20pF is recommended.

    Regards,

    ChrisO

  • 0 in reply to Chris Oberhauser66
    Prodigy 30 points

    Dear ChrisO

    In documentation September 2013 have 20pF capacitor in both pins ( external oscillator) to ground, but in a document of September 2015 and online document don't have any capacitor. But I tried in two conditions without result.
    The pin crystal out appears 0V. Thanks in advance .

    Carlos

  • 0 in reply to Carlos Scorzato
    TI__Genius 14270 points
    Hello Carlos,

    There are a few things to check. First, every crystal has its own recommended capacitor settings; these value should be used. The previous version of the datasheet recommended 20pF as that was a common value for the caps, but some crystals may need a different value. You should use the value recommended by the crystal manufacturer for that specific crystal you are using.

    In addition, crystals are very sensitive to capacitive loading; so make sure that you are not inadvertently loading the crystal.

    Regards,

    ChrisO
  • 0 in reply to Chris Oberhauser66
    Prodigy 30 points

    Hello ChrisO
    I agree with you about capacitive load, in my opinion this is not a real problem , because in pin 15 don't have any voltage to excitation crystal.
    I changed the value of capacitors (10 to 47pf). I change the IC and problem repeated.
    I'll use one external clock to check the all of IC functions..
    Regards
    Carlos