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LMX2595EVM: snau219b

Kevin Zheng
Prodigy 10 points
Part Number: LMX2595EVM
Other Parts Discussed in Thread: LMX2595, LMK61PD0A2, LMX2485E

Hello Sir,

We plan to use two PLL  to generate an 12.8GHz LO.

Use SYN1 to generate the 100 MHz , use the SNY2(LMX2595) (with the 100MHz reference)to generate a final 12.8GHz LO. There is an outside 10MHz or 50MHz for external reference.

We are trying to find the SYN1 which could provide an 100MHz reference to the LMX2595.

The goal is to get the 12.8GHz LO synchronize to the external 10MHz.

 If we use the reference pro LMK61PD0A2 to generate the 100MHz reference, we are not sure how to synchronize the 10MHz reference?

  Is that possible to use the Synchronize pin of the LMX2595?

 

 

Best Regards,

 

Kevin Zheng
RF Engineer

  • 0
    TI__Guru* 92100 points

    Hi Kevin,

    Did you mean you want Syn2 to synchronize with a 10MHz reference?

    there are two way to achieve this goal:

    1. use the 10Mhz reference as the input clock to Sync2. Phase noise will not be optimum as the fpd will be at most 20MHz.

    2. use the 10MHz reference as the input clock to a PLL+ VCXO(100MHz), output will be a clean 100MHz clock. Feed this clock to Sync2, and Sync2 will be synchronized to the 10MHz reference.

  • 0 in reply to Noel Fung
    Prodigy 10 points

    Thank you for reply. Agree. The first option phase noise won't be good as the fpd will be at most 20MHz.

    We prefer the second option , any PLL+VCXO(100MHz) you recommended? The LMK61PD0A2 won't work unless some function from the LMX2595 synchronize pin.

    Best Regards,

    Kevin

  • 0 in reply to Kevin Zheng
    TI__Guru* 92100 points

    Hi Kevin,

    You can use LMX2485E as the VCXO PLL.

    100MHz VCXO is a very common part, there are many choices from the market. You should pick something that meet your phase noise requirement at 12.8GHz.

    the LMK61 is a PLL-based clock generator with built-in crystal and PLL/VCO, it does not use your 10MHz clock, so it is not able to synchronize the 10Mhz clock.