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ADF4360-1 behavior at 2098 MHz (edge of VCO bands) during REFin drift

Hi,

How would ADF4360-1 behave when frequency is set to 2098 MHz (which is right on the edge of VCO bands) and REFin is drifting within +-1% (see picture from the datasheet below). Will it lose lock or switch the VCO band? 

Regards,
Ivan

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  • Ivan,  That is a typical plot of typical part at typical temperature.  That VCO transitions in the plot will vary some over Process Voltage and Temperature.  I have not worked on the ADF4360 directly, but I'm going to assume its VCO calibration is like our other PLL/VCO parts.  Basically, the integrated PLL/VCOX have a a lot of narrow band VCOs, and the VCO calibration uses the reference frequency, PLLs Ref divider, and PLLs N or feedback divider to select a VCO that will work for the desired frequency.  So any change to the reference frequency, the Ref divider, or N divider will result in a new desired frequency, which will usually require a new VCO calibration to find the correct VCO for the new desired frequency.

    From your description, it sounds like the customer is sweeping the reference frequency +/-1% to change the output frequency +/-1?  Typically these integrated PLL/VCOs are not great for frequency sweep applications due to the VCO calibration process.  For most sweep applications we recommend a stand alone PLL, with a wider band VCO that covers the desired frequency range of the sweep.  

    Maybe something like the HMC586 with the LTC6947 w/ integrated output divider would work?

    Chris

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  • Ivan,  That is a typical plot of typical part at typical temperature.  That VCO transitions in the plot will vary some over Process Voltage and Temperature.  I have not worked on the ADF4360 directly, but I'm going to assume its VCO calibration is like our other PLL/VCO parts.  Basically, the integrated PLL/VCOX have a a lot of narrow band VCOs, and the VCO calibration uses the reference frequency, PLLs Ref divider, and PLLs N or feedback divider to select a VCO that will work for the desired frequency.  So any change to the reference frequency, the Ref divider, or N divider will result in a new desired frequency, which will usually require a new VCO calibration to find the correct VCO for the new desired frequency.

    From your description, it sounds like the customer is sweeping the reference frequency +/-1% to change the output frequency +/-1?  Typically these integrated PLL/VCOs are not great for frequency sweep applications due to the VCO calibration process.  For most sweep applications we recommend a stand alone PLL, with a wider band VCO that covers the desired frequency range of the sweep.  

    Maybe something like the HMC586 with the LTC6947 w/ integrated output divider would work?

    Chris

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