AnsweredAssumed Answered

AD9912 Loop Filter

Question asked by TimW Employee on Feb 17, 2016
Latest reply on Feb 21, 2016 by LouijieC

I have a Rev. A eval board dated 2006.  It appears that the loop filter components C88 and C83 are not populated, which would make only R98 part of the 'filter'.  This board functions well with 25MHz input, and a x40 multiplier, but I'm not sure why?  It doesn't function properly with 60MHz input, multiplier of 16.  I'm also not sure how C93 and C53 are functioning.  They are supposed to be decoupling caps for VDD_SYSCLK.  What's the blue wire doing?  If those are decoupling caps (C93,C53), then the blue wire is grabbing ground, which goes against the data sheet loop filter being pulled up to VDD_SYSCLK.  What gives?

 

Capture.PNG

 

Capture1.PNG

Capture2.PNG

 

Thanks,

Tim

Outcomes