AnsweredAssumed Answered

ADF4351 reference spurs due to PFD frequency

Question asked by Chris449 on Jun 24, 2015
Latest reply on Jun 24, 2015 by rbrennan

Dear all,


I am using the ADF4351 PLL with the following setup

  • Reference frequency = 26 MHz
  • Integer-N PLL
  • Output frequency = 2470MHz
  • Disable doubler
  • disable divide by 2
  • R = 1
  • 25kHz loop filter for CP = 2.5mA


CP is set to 0 => reference spurs at +/-26MHz < 87.5dBc

CP is set to 15 => reference spurs at +/-26MHz < 81.3dBc


In Table 1, spurious signals due to PFD frequency is specified at -80 dBc.


Does it mean that the reference spurs is at -80dBc? Does it take into account possible feedthrough?


Thank you.