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ADV7343 noise

Question asked by cdb on May 17, 2011
Latest reply on May 18, 2011 by cdb

I'm trying to use an ADV7343 in combination with an ADV7184 and I'm encountering significant random noise spikes in the output CVBS and Luminance signals from the ADV7343.  These are spikes of about 1V ( the full amplitude of the signal).  They also spike downward to ground level.  On the Luminance signal I sometimes see these spikes during the horizontal sync and blanking period (the period that would be the color burst on a CVBS signal).  I see these noise spikes when I'm sending video from the ADV7184 through the ADV7343 and also when I tell the ADV7343 to output a color bar test signal or a black test signal.

 

I've carefully checked for noise on the loop filters and compensation caps and I've checked the values of the components for those circuits and everything looks fine.

 

On the video the noise looks like white or black spots usually near (can be above, below, or next to) sharp transitions in the video such as lettering on a dark background.

 

I'm using the parts in 8 bit 4:2:2 ITU656 mode with SFL enabled.  The crystal on the ADV7184 is 28.63636 MHz and its LLC clock to the ADV7343 (CLKIN_A) is 27 MHz.

 

I'm programming the ADV7343 I2C registers after a reset to:

 

0x56 0x00 0xfc

0x56 0x01 0x80

0x56 0x80 0x10

0x56 0x82 0xcb

0x56 0x84 0x06

0x56 0x87 0x20

 


Any suggestions?

 

Carl

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