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ADF4360-2 PLL unlocking issue at High temperatures

Question asked by limn on Feb 2, 2017
Latest reply on Feb 10, 2017 by icollins

Dear sirs,

 

We've been experiencing a PLL unlocking issue at temperatures close to +82C.

Application info as follows:

   Output freq: 2012MHz

   PFD Freq=2MHz, Ref freq=28MHz

   Presc=16/17

   Band Sel div=8

   Icore=15mA, Ibuff=11mA

   R Reg : 340039

   Ctrl Reg: 493128

   N reg: 3e3a

Output matching network : 47nH (Lbias), Cseries=10pF, L=4.3nh  (matching optimized for our pcb)

Please note that during the unlocked state

   VCO is functional (as evaluated in free running )

So we conclude that the Unlocking state is associated with a PLL issue.

If we decrease the differential pair tail current to 7.5mA , the issue disapeares.

If we increase the Icore to 20mA (although not recomended for that RF output frequency), keeping tail current to 11mA , the issue also disapprears.

Please advise ASAP.

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