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LMX2592: 10 GHz LMX2592

Gianni Chiodo
Prodigy 50 points
Part Number: LMX2592


I need to generate frequency in the range 10,011 to 10,437 GHz my reference will be 106,5 MHz so an integer PLL.

Can i use LMX2592 alone ( i can accept out signal even at -10 dBm) or i have to add a 2X multiplier ?

The LMX2592 alone will allow 106,5 MHz as Fpd allowing 106,5 MHz channel the insertion of 2X multiplier force me to divide by 2 the reference in order to have the same channeling .

Supposing a very good reference what phase noise at 1 and 10 KHz is possible?  Please both solution 5 or 10 ghz output.

Thanks in advance

  • 0
    TI__Guru** 110920 points
    Hi Gianni,
    Max. output frequency of LMX2592 is less than 10GHz. You can operate it at 5GHz and get the desirable 10GHz carrier from the 2nd harmonic.
    At 5GHz output, assuming you have > 100kHz loop bandwidth, the phase noise at 10kHz offset could be closed to -110dBc/Hz. 1kHz offset phase noise will definitely depends on the reference clock.
  • 0 in reply to Noel Fung
    Prodigy 50 points
    Thanks for the info actualy we are using a competitor but -110dbc/hz is attractive even with the degradation of the 2 armonics.
    We will use the single ended I/O. The output unused can be left open ? Is necessary to connect the 50 ohm resistor ?
    In case of 18 nH on output pin is mandatory to apply the same load or i can mix 50 ohm on the unused and 18 nH on the other pin plus the serie capacitor to the following stage? How much is sensitive the device to a load mismatch?
    The input unused must be capacitive coupled to 50 ohm or i can connect the capacitor to GND?
    We are designing a proto PCB with our user devices connected and space around the LMX2592 is very populated so any component reduction is mandatory.
    Best regards Gianni Chiodo
  • 0 in reply to Gianni Chiodo
    TI__Guru** 110920 points
    Hi Gianni,
    We recommend to use the same type of pull-up for both pins. The unused pin should be AC-coupled to ground via a 50 ohms resistor.