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ADV7391 CVBS Generation Problem

Question asked by PGUTTINL on Jul 18, 2017
Latest reply on Aug 2, 2017 by PGUTTINL

Hello,

 

We have many problems with PAL CVBS output generation using ADV7391 when the input frame contains white pixel at the end of lines.

 

The input frame format is BT656 (with embedeed EAV/SAV).

The configuration of ADV is:

Register    Value
0x00            0x10
0x01            0x00
0x02            0x20
0x88            0x00
0x87            0x00
0x9D           0x00
0x9E            0x00
0x9F            0x00
0x80            0x11

0x82            0xC3
0x8C            0xCB
0x8D            0x8A
0x8E            0x09
0x8F            0x2A

 

So, when we add white (thanks to a light on our CMOS Sensor) on the image, the first consequence is black line on the screen:

We can see these lines on the signals:

 

If we add more white on the image, the monitoring screen loss the synchronisation and following signal are acquired:

 

Long Synchro:

 

4.43Mhz unexpected oscillation before synchro:

 

We also notive that our white level is 735mV instead 700mV, but we added a gain to reduce this point and our problems were still notived.

 

Do you identify the root cause of these problems ?

 

EDIT: This is a custom board and I don't have the EVB.

 

Regards,

 

Perry

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