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PLL Selection

Hello,

I'm looking for a part/circuit that has an output frequency range of 5MHz to 100MHz with 1KHz channel spacing.  Ie was originally looking at fractional-n PLLs, but I'm thinking integer-n would probably work as well.  The application involves trying to phase align my reference clock with my received data. I plan to use a micro to control the PLLs frequency to bring the clock and data into alignment.

I quickly tried playing with ADIsimPLL and it recommended the ADF4156 for a fractional-n and whole list of parts for integer-n.  I also tried looking at the ADF4360-9, but apparently the frequency range cannot be accomplished with a single output divide value.

A quick side note, ADIsimPLL doesn't seem to take into account the output divider on the ADF4360-9 when specifying Fmin, Fmax, and channel spacing.  Instead, I think you have to specify the VCO output frequency before the divider, which isn't very helpful if you are trying to use ADIsimPLL as a selection tool.

- Kevin

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  • Hi Kevin,

    To achieve the 1kHz resolution across the full-band I think he will have to use a fractional-N PLL, like the ADF4156. The problem would

    be sourcing a VCO that can cover his range of 5MHz to 100MHz.

    One circuit suggestion would be to use a ADF4156 + 50MHz to 100MHz VCO. The VCO output frequency could then be input into

    the ADF4002 for further division to get 5 - 50MHz. 1kHz resolution should be achievable in this case.

    Note, when using the ADF4156 at these low frequencies the slew-rate specs. on the RFIN pin need to be met.

    The ADF4360-9 will not cover the full range without any gaps just by using one inductor. to do this

    would require an octave band tuning range (like on the ADF4350 for example). He could possibly achieve the full tuning range with a > 1kHz

    resolution by switching external VCO inductors using pin-diodes as is done in variable matching circuits as an alternative to ADF4156+ ADF4002.

    --Austin

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  • Hi Kevin,

    To achieve the 1kHz resolution across the full-band I think he will have to use a fractional-N PLL, like the ADF4156. The problem would

    be sourcing a VCO that can cover his range of 5MHz to 100MHz.

    One circuit suggestion would be to use a ADF4156 + 50MHz to 100MHz VCO. The VCO output frequency could then be input into

    the ADF4002 for further division to get 5 - 50MHz. 1kHz resolution should be achievable in this case.

    Note, when using the ADF4156 at these low frequencies the slew-rate specs. on the RFIN pin need to be met.

    The ADF4360-9 will not cover the full range without any gaps just by using one inductor. to do this

    would require an octave band tuning range (like on the ADF4350 for example). He could possibly achieve the full tuning range with a > 1kHz

    resolution by switching external VCO inductors using pin-diodes as is done in variable matching circuits as an alternative to ADF4156+ ADF4002.

    --Austin

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