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LMX8410L: VCO Range uncertainty 7.5 to 7.7 GHz

Charles Luke
Intellectual 270 points
Part Number: LMX8410L

From 7.4.1.1

Although the majority of devices have a VCO range of 7.5 to 15 GHz, this is NOT ensured. In reality, the VCO is tested for sure to cover 7.7 to 15 GHz. In the range of 7.5 to 7.7 GHz and 15 to 15.4 GHz, the VCO will cover at least enough frequency to cover a factor of two in frequency. What this means if using the internal mixer is that if one wants a LO frequency of 7.6 GHz, then first try this using the poly mode and VCO frequency of 7.6 GHz. However, if the VCO can not do 7.6 GHz, then one has to try DIV2 Mode with the VCO at 15.2 GHz.

"If the VCO can not do" how do you define that? Loss of lock? 

Also, if I have to go with the VCO = 2xLO instead of VCO = LO, what's the penalty for doing that?

  • 0
    TI__Mastermind 27581 points

    Charles,

    Yes, in this narrow range, you have to try it and see if it locks, if not , use the other way.

    When you compare DIV2 and Poly Mode (I'm reading this from our TICSPro software), you have to use DIV2 if the VCO frequency is too high, and use Poly if the VCO frequency can hit the LO frequency directly.

    Now suppose you are at 7550 MHz and both DIV2 and Poly mode can hit this.  Then I am no sure, but I think that the DIV2 would have better noise performance.

    Regards,

    Dean