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ADF4351 lock unstable 

Question asked by sss on May 18, 2016
Latest reply on Jun 7, 2016 by rbrennan

Hi all,

 

When evaluating the EVAL-ADF4351EB1Z, sometimes it happens unlocks.

 

PLL setting is following,

INT-N mode

fout:390MHz-420MHz

PFD:100KHz

REF:48MHz

Loop band width:2.71kHz

Phase margin:>45 deg

prescaler input < 3.6GHz

 

PLL Lock condition is following,

1.fout is <400MHz

prescaler:4/5 >>> lock

prescaler:8/9 >>> lock

2.fout is >400MHz

prescaler:4/5 >>> unlock sometimes

prescaler:8/9 >>> lock

When selecting the prescaler 8/9 fixed, PLL lock is stable in all frequency bandwidth.

 

Q1.

Is the prescaler 8/9 fixed correct behavior ?

Q2.

What are the parameters that should we be re-consideration?

 

Please advise to us.

 

Best regards,

sss

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