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ADV7181C  full scale luma

Question asked by Vladi215 on Oct 31, 2012
Latest reply on Nov 13, 2012 by FrankK

Please assist me with the following problem-

 

I am using ADV7181C decoder. I configure it according to the attached "un_configuration.bmp" file.

 

By using QUANTUMDATA 802BT BAR GENERATOR I inject to the components inputs RGB SOG signal with only G component active. The injected signal has a maximum LUMA component, in other words I inject 714 mili volt video signal and minus 286 mili volt sync signal.

 

At the outputs of the device we expect to see maximum LUMA values of FFh however we receive the value of D8h as you can see at the attached "un_signal tap.bmp" and " file.

 

 

I also attach scope screen shots of the signal measured at the input of the decoder after the AC COUPLING capacitor, files "un_decoder_input_after_capacitor_1.bmp","un_decoder_input_after_capacitor_2.bmp"

And before the  AC COUPLING capacitor files, "un_decoder_input_before_capacitor_1.bmp","un_decoder_input_before_capacitor_2.bmp"

 

I have noticed that by manually changing the bias current value using IBIAS_SET[4:0] register I can configure the output signal to it's full scale, however I do not know why is it happening and what is the source of the problem.

 

 

Why does the component's outputs don't match the signal in it's inputs as expected?

Thank you,

 

Vladi

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