AnsweredAssumed Answered

AD725 noise on PAL/NTSC output

Question asked by joeka on Mar 4, 2013
Latest reply on Mar 15, 2013 by GuenterL

Hi,

 

I'm working with AD725 component to output a live video in PAL or NTSC. I succeed in converting VGA signals into PAL and NTSC by creating hsync and vsync signals and interlacing datas. Now it seems that I have a noise problem on displayed video. I think screenshots are the best way to describe it :

tb.bmptb_ad725.jpg

 

On the first picture, a screenshot of what i'm "supposed" to display with AD725.

On the second picture : what I'm currently diplaying

(Verticals white line are due to another problem independent of displayed video)

 

On second picture, we can see vertical lines that are not supposed to be here. I really don't know from where it comes but the displayed video is really poor with it. It appears to be more and more visible when displaying dark fields as we can see in the next pictures :

tb2.bmp

tb2_ad725.bmp

I already checked schematics compared to AD725-EVB. Decoupling seems to be ok. I have no idea where to look to solve this problem.

This problem is the same with PAL and NTSC output. I'm using composite output.

Any idea ?

 

Thank you for your help.

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