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ADV7393 luma and color scaling

Question asked by Hurter on Nov 26, 2014
Latest reply on Dec 11, 2014 by GuenterL

Hi

I am using 2 video output ADV7393's on my pcb. The video ADV7393 is setup to
output normal standard definition video that is buffered to 2 output with a
op-amp, AD8063ART and AD8131ARMZ.

Now I have video out and it looks ok on a monitor, but I am not in the 1Vp-p
specification because the gain on my output op-amps are incorrectly set. I am
688mVp-p instead of 1Vp-p with 75 ohm termination.

1. What will the side effects be if I use the scaling function, registers 0x87,
0x9C-0x9F on the ADV7393 chip?
I can see that when I can lift the signal to 1Vp-p but I also see the the sync
and burst side of the signal did not scale to the same ratio as the analog
video side.
2. If I can use the scaling, should I scale only the luma, or should I scale
the color as well?
3. If I can use the scaling, can I use register 7% gain as well or must I leave
on normal gain?

I know the ideal would be to change the op-amp's gain but the pcb's are already
in the field and build into systems. Quite a job to get to and I  would prefer
to fix this with a software update.

Thanks in advances
Hurter Bornman

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