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LMK05318B: APLL1 with fractionnal divider

Christian Sillans
Prodigy 50 points
Part Number: LMK05318B

Hi everyboby,

I use LMK05318B for a jitter cleaner following an analog reciever.

The XO input is connected to a 10.7MHz signal and I want to generate and deistribuate clean 10MHz signal.

My first idea was to use APLL1 with BAW VCO  for very low phase noise, but I've read on the forum that we can use APLL1 with integer divider only ?  After reading the data sheet, I must admit that I do not understand why ?

And further, with the TIC Pro tool, I can get such frequency as shown hereafter?

What is the real functionnement ?

Many thanks for your help

Christian

  • 0
    TI__Expert 8585 points

    Hello Christian,

    APLL1 on the LMK05318B can support any output that has an integer relationship with the 2500 MHz BAW VCO on APLL1. Therefore, it will have no issue outputting a 10 MHz clock (2500 MHz / 250 = 10 MHz).

    APLL1 has a fractional feedback divider as shown below which will allow you to use any XO input frequency and obtain the 2500 MHz APLL1 VCO frequency.

    Please note the XO input frequency must be 10 MHz to 100 MHz.

    The LMK05318B also has channel dividers to divide down the APLL VCO frequency to achieve the required output frequency. The channel dividers are always an integer value.

    Therefore, to obtain the 10 MHz output clock from the 2500 MHz APLL1 VCO, you will require a channel divider of 250 (which is an integer value).

    Regards,

    Kia Rahbar

  • 0 in reply to Kia Rahbar
    Prodigy 50 points

    Dear Kia,

    Many thanks for this quick answer.

    Christian