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CDCM7005: cdcm7005

Carles Torrents
Prodigy 45 points

Part Number: CDCM7005

We have had to change the VCXO Vectron VX-705-ECE-KEAN-100M000000 used with the CDCM7005 due to a lack of stock and we have changed to the Abracon ASG-P-V-A-100.000MHz.

With the first one we don't have any problem to synvhronize. With the secon one we have important problems.

The problem identified is that the Texas CDCM7005 do not provide Control Voltage output until it has a signal at its input, and this signal it is not provided by the Abracon VCXO until it has Control voltage, producing a blocking situation (This did not happen with the Vectron VCXO because it provided always signal at its output). 

We have initially solved this problem by using the Preset Charge Pump output voltage of the CDCM7005 which forces a voltage at the output of the Control Voltage. This allows the VCXO to start providing signal at its output.  Removing this preset immediately, it is obtained, apparently, a way to break of the blocking status. Unfortunately, this methode do not always  work, due to it is not controlable the timing of the process.  Do you have any suggestion on the CDCM7005 control to solve the problem?

  • 0
    TI__Expert 5370 points
    Dear Carles,

    apology for the delay. I am looking how to potentially adress the issue you describe.

    Regards, Simon.
  • 0 in reply to Simon Damphousse
    TI__Expert 5370 points
    Dear Carles,

    I looked at the issue you describe.

    I have a few suggestions:

    1) You may consider a replacement for ASG device.

    2) THe 7005 device can provide you a status bit for the VCXO health (pin 22 of the QFN STATUS_VCXO), at start up, you can force the preset mode (mid rail voltage) and wait until pin 22 goes high so you know you have a valid frequency.

    3) You may try to go in and out of the preset mode with various duration to see how long it takes before the ASG start. That will provide you a time frame on how long to wait in preset mode before going active.

    I hope this helps,

    Regards, Simon.