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How sensitive is the ADV7181C  external loop filter?

Question asked by ianstedman on Dec 13, 2011
Latest reply on Jul 24, 2012 by DaveD

Hello,

 

I posted a while ago relating to problems with the ADV7181C sampling SVGA (800x600) video @ -40C. I thought the problem was resolved but

we have had trouble repeating the test results on other modules. A number of investigations are under way.

 

For the external loop filter, there is a 1.69K resistor, in series with a 82nF capacitor. I could not find an 82nF COG dielectric part so we use  68nF and 15nF

capacitors. They have a 5% tolerance on capacitance with a temperature coefficient of 0.1% with temperature as expected, could this affect the operation of the circuit?

 

The end effect on the display looks like the line length is varying on alternate lines. If required I can post a picture.

 

In a related investigation, we have discovered that the +3.3V supply is somewhat noisy in our system. Can noise on the +3.3V supply affect the PLL operation?

 

Ian

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