AnsweredAssumed Answered

ADF4007 PLL error output pulsed?

Question asked by zwarren on Nov 10, 2014
Latest reply on Nov 14, 2014 by rbrennan

I am trying to get an error out from this ADF4007 board for feedback (and I have a filter in place).  For the sake of simplicity, I'm using:


RF in: 2GHz

RefIn: 125 MHz (which goes to 62.5 with the fixed R divider at 1/2)

Ndivider = 32

this is not a closed loop  - just observing the error out (Vtune after filtering)


When the two signals are out of phase, I get 0V output.  When I change the frequency by a small amount (a few Hz), I get pulsed output that looks like a dispersive error signal, at the rate of the frequency difference.


However, I was expecting a constant voltage output based on the phase difference.  Is this the characteristic of PLLs - a pulsed error signal?  I have been having trouble finding anything in journals about this - I have to understand it in order to finish the feedback.