high quality s-video CXA1645

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sammy
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Joined: Thu Dec 08, 2005 3:13 pm

high quality s-video CXA1645

Post by sammy » Mon Jan 14, 2008 12:50 pm

I succesfully did the RGB mod on a mini snes but since the S-video mod seems to be too difficult for me I'm going to use a CXA1645 ic salvaged from an old playstation.

I've studied the datasheet and constructed an appropriate circuit for my application but there's one thing I don't quite understand yet.
I refer to the datasheet: http://www.promelec.ru/pdf/cxa1645p.pdf

On page -12- they speak of a necessary Subcarrier signal:
The SC input (Pin 6) can be either a sine wave or a pulse in the range from 0.4 to 5.0Vp-p.
However, when a pulse is input, its phase may be shifted several degrees from that of the sine wave input.
In the IC, the SC input is biased to 1/2 VCC. Accordingly, when a 5.0Vp-p pulse is input and the duty factor
deviates from 50%, High- and Low-level pulse voltages may exceed VCC and GND in the IC, which causes
subcarrier distortion. In such a case, be very careful that the duty factor keeps to 50%.


Does that mean I have to make this signal myself or can I get it of the Snes motherboard?

If I can't then:
Because it says a pulse might give problems I plan on using a 3.0V peak to peak sine wave, but I have no idea what frequency it should be. The datasheet doesn't seem to mention anything about it either.

My schematic (basically the application circuit from the datasheet):
Image

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