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LM5143-Q1: SYNCIN frequency range

Stephen Oberholzer
Intellectual 895 points
Part Number: LM5143-Q1
Other Parts Discussed in Thread: LM5143

Good morning,

It is wonderful to see you are implementing a phase locked loop for synchronising the LM5143.

This is just what I need.

The frequency range for the SYNCIN signal is specified as -20% and +20% of the nominal set frequency.

This range is unfortunately right at the limits of my requirement.

Would the LM5143's SYNCIN be able to lock onto a -30% to +30% variation in frequency, to give me some margin? 

If yes, this will give me peace of mind and make me eager to use the LM5143 in my new design.

Another question I have: What is the duty cycle of the SYNCOUT signal?

If it is 50%, it will be wonderful - unfortunately it is not specified on the datasheet.

Your urgent reply will be appreciated.

Sincerely,

Stephen.

  • 0
    TI__Expert 8245 points

    Hi,

    If the datasheet specify the variation, it's better to follow it because it's guaranteed and might have some issues or cannot work on other conditions.

    From its datasheet, SYNCOUT is a logic level signal with a rising edge approximately 90º lagging HO2, it might be 50% duty approximately base on test results of some other similar devices. You can verify it in your own bench since there is no spec on its datasheet.

  • 0 in reply to Iven Su
    Intellectual 895 points

    Hi Iven,

    Thank you, I understand fully what you are saying.

    Can we not please ask the designer of this ic my questions, since he would give a definite answer.

    It will take too long to obtain a sample, build it into a circuit and to find out practically whether the SYNCOUT is 50% duty cycle.

    The designer will know immediately.

    Regards,

    Stephen.

  • 0 in reply to Stephen Oberholzer
    TI__Expert 8245 points

    Hi,

    I will send your question to dedicated engineers, once get their reply I will update it on this post. At the same you can apply an evaluation board from ti.com to verify it because the SYNC out is just designed for SYNC. A constant duty cycle is not guaranteed because it's not on design spec or datasheet. Thanks for you consideration. 

  • 0 in reply to Stephen Oberholzer
    TI__Expert 8245 points

    Hi,

    I have checked it with dedicated engineer, the Syncout duty cycle is 50%.