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Posted by Richard Crowley on 11/25/06 10:59
"Alx" wrote ...
> I've got this problem on all the Video Out( 1, 2, 3, 4, 5).
> The Video captured clip is from a Playback (video recorder in pause
> mode) with a live signal in the Video IN and Channel 2 selected on the
> video Mux.
>
> The problem disapear on all Output when I unplug the live signal on
> the
> main Video IN
> or when I switch to Chanel 1 on the video Mux, but, in this case, it
> seem to lost a bit of brightness in the Video Out 1.
> The problem disapear on Video Out ( 2, 3, 4, 5 ) when I switch to
> Chanel 2 on the video Mux, but got a still ghosted vertical bar on the
> right on the Video Out 1.
>
> More the Video live signal is bright more the interference is
> perceptible.
You have leakage through the switching part of your circuit.
Whether this is from the fundamental capabilities of the chip,
or whether it is related to the physical layout cannot be
determined from the limited information you posted here.
Designing high-frequency circuits (such as video) is not a
trivial thing to get right. Particularly for second-order effects
like your leakage here. You appear to have leakage both through
the switch from the unselected input, AND leakage from one
input to the other.
Study some of the chips and application notes (suggested PC
board layouts, etc.) for video switching chips such as those
made by my neighbors down the street: www.maxim-ic.com
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