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
Band Sel div=8
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.