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(ADV7390)Noise output from the device.


Hi !

I have some question about ADV7390.

Some kind of noise is output from ADV7390.

I am using ADV7180-ADV7391 Eval-board and using "CVBS auto detect" script.

=> I attached the script file.

And I zoomed the waveform.

The BT.656 data is output from ADV7180 and at the EAV and SAV point , ADV7390 output some kind of noise.

Also I setup the ADV7180's resister, 0x0C to "Force free run mode" and "Output 100% black".

Why does this noise output from ADV7390?

And also to prevent outputting this noise what should I do?

Is it possible to erase this noise by setting resister?

I want to know this because our customer have this issue.

I will attach customers waveform.

Also at the display, blue line is in the display.

Our customer think this happens because of the ADV7390's noise output.

I will check about this(display image) connecting ADV7180-ADV7390Eval board to other Eval board

and moving the image area to check this will happen or not .

But I am out this week so it will be next week.

If you can tell me why this will happen and how to solve this problem, it will help us and our customer very much.

Best regards.

Kawa

attachment.zip
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  • Initially I would not say this is directly related to anything the ADV7390 is doing.  This looks like the source or the sync is inserting a noise spike into the system.  And by system I mean the entire source - ADV7390 - sink as a system.  By the placement of these spike is looks like it's related to the end of the back porch and the start of the front porch.

    The extra vertical line of the left side of the screen might be because the sink is not interpreting the back porch correctly.  Normally sinks determine the left edge by timing from the leading horizontal edge.  Maybe the souce can make the back porch shorter or horizontal pulse shorter.

    To check the ADV7390 is generating the spike I would ground the scope directly on one of the ground pins of the ADV7390 and probe the DAC outputs.  Make sure that this is the only ground point of the scope. 

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  • Initially I would not say this is directly related to anything the ADV7390 is doing.  This looks like the source or the sync is inserting a noise spike into the system.  And by system I mean the entire source - ADV7390 - sink as a system.  By the placement of these spike is looks like it's related to the end of the back porch and the start of the front porch.

    The extra vertical line of the left side of the screen might be because the sink is not interpreting the back porch correctly.  Normally sinks determine the left edge by timing from the leading horizontal edge.  Maybe the souce can make the back porch shorter or horizontal pulse shorter.

    To check the ADV7390 is generating the spike I would ground the scope directly on one of the ground pins of the ADV7390 and probe the DAC outputs.  Make sure that this is the only ground point of the scope. 

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