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ADV7403 unstable TLLC w/nonstandard video

Question asked by JoeL Employee on Mar 16, 2017
Latest reply on Apr 3, 2017 by DerekBurke

Hi,

 

My customer has configured the ADV7403 for an RS-330 interlaced video input. One line of video is 63.4921us (1/30Hz/525lines).  With 1224 samples per line and 2x oversampling the modified TLLC value was calculated to be 19.278MHz. (0x4C8 TLLC register value).   ADV7403 register configuration script has been attached.

 

The issue they are seeing is that the top lines (approx. 4) of active video do not have a completely stable TLLC (scope plot attached: Line12.png) whereas subsequent lines are stable (Line128.png).  Plots were taken with a Tek scope with video triggering on NTSC setting.  Line numbers on plot aren't entirely accurate because of nature of RS-330 (lack of serration) but it is stable and repeatable.  Input video is a grill_11 pattern from a Quantum Data. 

 

They would like to understand the cause of this instability and if there are any recommendations for eliminating it.

 

Thanks,

Joe

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