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(ADV7282AM)CVBS-diff lock problem.

Question asked by donadona999s on Jun 27, 2018
Latest reply on Jul 6, 2018 by donadona999s

Hi !

 

Our customer have some trouble at their ADV7282AM system.

They are not using ADI EVAL board. They are using their own PCB board.

But the script is 100% same as ADI recommend script.

We are trying to connect customers video source to ADI EVAL board next week.

They will use ADV7282AM for automotive rear camera interface.

 

Their problem is this.

*************************************************************************************************************

①Immediately after register setting, seemingly normal color bars are displayed.
 However, since analog noise occurs sporadically, it seems that some problems already exist.

②When ADV7282A-M lock to CVBS-Diff, the status bit is this.

 0x10 => 0x05

 0x11 => 0x43

 0x12 => 0x00

 0x13 => 0x69

③After a while, the image display is disturbed. (It may be several seconds, sometimes a couple of minutes later)

 When checking the status register when the video display was disturbed, the lock was lost.

④When several minutes elapsed again, there was a case where it returned to a normal image.

⑤When resetting the IC and setting the register again, a normal color bar is displayed and return to ① as I wrote above.

 

We already checked that ADV7282AM AIN pin clamp looks there is no problem.

We checked CLK jitter but there was no problem.

*************************************************************************************************************

 

We will confirm the input signal in more detail.(ex. sync, sub carrier...)

They are using fast switch mode and the disable fast switch after system start but nothing changed.

We asked to my customer to change VID_STD to NTSC-M buy the problem didn't disappear.

They are connecting 

DVD player => ADA4433-1(change single to differential) => ADV7282AM => SoC > Monitor

ADA4433-1 circuit is this.

(ADA4433-1) To connect ADA4433-1 to ADI Video decodor 

Also they changed 150Ohm register to 75Ohm.

(Video decoder)When inputting full differential, is the network resistance really 150 ohm? 

We already know that ADV7282AM status bit is something wrong and when they use free run mode there is no problem so we think it is not SoC or Monitor problem.

 

Do you have any idea what is the reason for this problem?

Do you have any advice for this?

Are there similar experiences?

 

Best regards

Kawa

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