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LMX2492EVM: What parts we need to change if we use LMX2491

Cedrick
Expert 8270 points
Part Number: LMX2492EVM
Other Parts Discussed in Thread: LMX2491

Hi, 

Good day. I hope everything is fine. 

Our customer wants to know which parts/components they need to install/remove if they will use the LMX2492EVM to evaluate LMX2491. It seems that they need to replace the VCO (U2p) however they want to make sure that all needed parts are ready before they evaluate it. 

I would appreciate your help on this. Thank you.


Regards, 

Cedrick


  • 0
    TI__Genius 11900 points

    Hello Cedrick,

    Both of these parts are pin-to-pin compatible. Please refer to the schematic.

    • Install R5 to connect output to RFout SMA
    • Install R14 and C5 for power to VCO and filtering
    • Install 0-ohm at R4pLF to connect to loop filter (you can adjust this if you want to use 4th order loop filter and also add C4pLF)
    • DNP R4_LF, to disconnect LF from U2
    • DNP R6 to disconnect U2 from RFout SMA and avoid any noise coming in from U2
    • Additionally, you can DNP L4 and L5 to powerdown U2 completely.

    Please also refer to https://e2e.ti.com/support/clock-and-timing/f/48/p/864377/3200428

    Thanks,

    Vibhu

  • 0 in reply to Vibhu Vanjari
    TI__Genius 16655 points

    Hello Vibhu,

    Good day.

    We just received a follow-up inquiry from the same customer on this. From the LMX2492EVM's schematic, the recommended oscillator’s frequency is 1400-1624MHz. Customer is asking if they use this oscillator, will they be able to reach 6.4GHz as LMX2491 works up to this frequency? Or, should they use another oscillator to reach 6.4Ghz?

    Thanks for the confirmation.

    Art

  • 0 in reply to Art Mecina
    TI__Genius 11900 points

    Hello Art,

    I do not believe so, U2p isn't populated on the EVM. I believe this is where they get the 1400-1624 MHz.

    The oscillator isn't necessarily a recommendation, it is more so a footprint for customers to populate their own VCOs. As different customers may be evaluating VCOs in different frequency ranges.Your customer will need to pick a footprint compatible higher frequency VCO.

    Thanks,

    Vibhu

     

  • 0 in reply to Vibhu Vanjari
    TI__Genius 16655 points

    Thanks for the immediate response Vibhu!

    The customer will be using the LMX2492EVM to evaluate LMX2491 and so has to populate the U2p.

    Did you mean that the customer can use an oscillator (VCO) of their preference as long as it matches the footprint?

    Do you have any recommended oscillator for them to be able to reach 6.4GHz on LMX2491?

    Thanks!

    Art

  • 0 in reply to Art Mecina
    TI__Guru** 108330 points

    Hi Art,

    The footprint of U2p is a very common VCO footprint, Cyrstek CVCO55 series VCO has a lot of frequency options. Customer should also be able to find their preference VCO with the same footprint easily from the market.