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Strange DE signal on Eval 7611

Question asked by yerffoeg on Nov 19, 2015
Latest reply on Nov 20, 2015 by GuenterL

I have been running this board for about a week. The display is now up and running and I am ready to put my pcb out for manufacture. However I still have a problem: The display starts to fail after about 30mins.

 

Looking at the DE signal on the board I can see postive going pulses on it. Symptoms are: No scripts just powered up, sw not enabled, the DE signal is 3.2vpk as to be expected. Board current about 185ma.

 

Load script, current rises to 365ma DE signal still looks good.

 

Apply HDMI from test gen and DE drops to about 1.5v and video? pulses appear on it that go to 3.3v. Remove HDMI and all looks fine again.

Current with HDMI connected is about 760ma.

 

The display has been running like this but over about 30mins the whole DE signal collapses down to about 800mv with about 300mv of video pulses on top of it. At this point the picture come apart.

 

Has the AD7611 failled or is something else going on?

 

Geoffrey Frost

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