AnsweredAssumed Answered

ADV7125 Vref Value

Question asked by hisel on Aug 31, 2015
Latest reply on Sep 1, 2015 by GuenterL

Hi everyone,

 

I use the schematics in Datasheet (Figure 10. Typical Connection Diagram) on my design except AD1580 zener.

 

I want to use adv7125 for composite video, so IOR and IOB terminated with 50ohm which is same impedance value with IOG. IOG is doubly terminated (150ohm and 75ohm load according to AN205) and Rset 530 ohm.

 

In this situation, Vref is 2.78 V (VAA 3.3V).

 

I expected to see ~1.235V level without using zener diode. What are the factors effect on level of Vref?

 

I also think that output video voltage level is different than I need to see because of Vref problem. Pk - Pk voltage is true but there is a minus offset.

 

Kind Regards.

 

Hasan

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