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ADV7611 video quality issue

Question asked by kaly on Oct 30, 2013
Latest reply on Oct 31, 2013 by GuenterL

I'm having some trouble with the ADV7611BSWZ HDMI receiver. The video quality issue that I'm seeing is that there are black/purple pixels that follows along color gradients. So, if I have a transition from blue to a lighter blue, the border between the two will have those mis-colored pixels. Solid color fields look fine. Also, in single-pixel on-off patterns, the video appears to swim a little. Edges in moving video also appear to waver a little. Other video inputs to my system are working fine, including video from a different 30-bit pixel bus. What's concerning is that we have this issue on some boards, but not on others.


The clock (27MHz) and power going to the ADV7611 appear to be stable. Audio coming from the ADV7611 also sounds fine, so I'm focusing right now on the layout of the video lines from the IC. I am noticing that the LLC output from the ADV7611 is only ~2.8V-3.0V at the IC pin and much smaller (~1.6V) after a series terminating resistor, so I'm trying to figure that out. Other outputs from the ADV7611 have the full 3.3V swing.


The 100 ohm traces between the HDMI connector, through the ESD IC, to the ADV7611 are about as short and direct as it can be, so I'm thinking that our 24-bit output is marginal. I've looked through the documentation for the ADV7611 but I didn't see any specific recommendations with regards to the layout of the pixel bus output, unless I've missed it.


My questions would be:

- are there layout recommendations for the pixel bus output? (trace length matching, max length, spacing, etc.)

- is there a register to strengthen the drive of the LLC pin?

- are there any registers that allow me to adjust the timing of the pixel data output relative to the LLC?

- anything else I might have missed, or should check?