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CDCM9102 - The delay time from power up to RESET for VCO calibration

Hiroshi Katsunaga
Mastermind 6480 points
Other Parts Discussed in Thread: CDCM9102, CDCM6100XEVM

Hello,

My customer has a question about CDCM9102.

[Background]

They generated a delay by applying a 47nF capacitor to gnd on the RESET pin.

They don't use the recommended crystal.(datasheet P.11 Table 1)

Their crystal is FA-238 (Epson).

They failed VCO calibration at some temperature conditions.

They want to get the appropriate delay in their crystal.

I introduced a method to identify the frequency settling by using signal source analyzer.

[Q]

Please tell me the frequency settling threshold where VCO calibration becomes certain, if stable (steady state) oscout frequency is 25MHz +/- 0ppm.

Best Regards,

Hiroshi Katsunaga

  • 0
    TI__Mastermind 20900 points
    Hello Katsunaga-san,

    you could try to use a bigger cap on the RESET pin to delay the calibration even more. Try times 10 or 100.
    What are the temp conditions that the device fails?

    best regards,
    Julian
  • 0 in reply to Julian Hagedorn
    Mastermind 6480 points

    Hello Julian,

    Thank you for your response.

    I show additinal information as follows.

    Their temperature conditions are as follows.

    　* Their test temperature range = -5deg to 60deg.

    　* The temperature condition that the device fails = around 15deg.

    They tried that they delayed the RESET trigger.

    　* 50ms delay -> NG

    　* 80ms delay -> OK

    They want to know the appropriate RESET timing.

    Therefore I measured the frequency settling sample waveform in CDCM6100xEVM.

    The measurement waveform as follows. (This is just sample waveform.)

    I measured this in a default conditions.

    [Q]

    For example, Does VCO Calibration not fail at the red arrow timing ?

    Best Regards,

    Hiroshi Katsunaga

  • 0 in reply to Hiroshi Katsunaga
    TI__Mastermind 20900 points

    Hello Katsunaga-san,

    after the crystal generates a stable frequency the calibration should work fine. i would recommend to use the longer delay to have the crystal oscillation stable.

    regards,

    Julian

  • 0 in reply to Julian Hagedorn
    Mastermind 6480 points
    Hello Julian-san,

    Thank you for your response.
    OK, I understood your comments.

    I will close this post.
    If they have any question in this matter, I will send e-mail to you directly.

    Thank you for your cooperation.

    Best Regards,
    Hiroshi Katsunaga