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ADV7123 do we terminate the RGB signals with series resistors?

Question asked by phan on Apr 29, 2015
Latest reply on Apr 30, 2015 by phan

I have an application that uses the ADV7123 for VGA output from an SoC. The SoC can drive the HDMI out or parallel out to the ADV7123.

Using a pattern generator at the input of the SoC through a ADV7842, the HDMI output looks perfect, but the VGA output is smeared over at both the leading edge and trailing edges of the signals. I have footprint in the RGB signals for series termination and would like to know if anyone has used the series termination on the RGB and if you have, how do you adjust the 75 Ohms terminations? Or if you have any ideas on what causes the smear of the signals.

Attached is a captured portion of the VGA output (1920x1080 @60Hz, 148 MHz video clock) with the black bars that show the smear over, and the waveform of RGB signal at the output connector.

 

Thanks,

Tai

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