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LMX2594: Frequency offset and unstable monotone of SYN output; LMX2594

Siddharth Shah
Prodigy 30 points
Part Number: LMX2594

Hi,

We have designed a Syn using the LMX2594 and on testing we are facing 2 issues.

  1.  An offset of around 40MHz
  1. For instance, for a RFout freq. 5000MHz we are getting 5041MHz similarly over the band with some increment in offset at more higher freq.

Monotone only when the charge pump gain = 0mA
  1. We are getting a wideband signal for a higher charge pump gain other than 0mA.
  2. While we checked this thing in Eval Board we were getting a good signal at 15mA, but at 0mA we were getting a offset of -80MHz (monotone)

What are the possible cause for this? Loop filter, OSc, RFout path? 

  • 0
    TI__Genius 11900 points

    Hello Siddharth,

    Are you using the EVM for this?

    What is your frequency plan? Fosc, Fpd, Fvco, RFout?

    When you use 0 mA charge pump gain, that is the same as open loop VCO and the frequency may not be stable.

    Does the device indicate lock? You can check this using MUXout pin.

    Thanks,

    Vibhu