LVDS issues … exactly the same lenght / impedance on all I/O lines and add 
common mode chokes on all lines aswell. 

 

Best regards

Amund

 

 

Fra: alfred1520list [mailto:alfred1520l...@gmail.com] 
Sendt: 15. oktober 2016 07:41
Til: EMC-PSTC@LISTSERV.IEEE.ORG
Emne: Re: [PSES] RE from Flat Panel ICs

 

Hi Eugene, 

Jokes aside, may be the meaning of general recommendations have different 
meanings to us so let's clarify that and see if it takes us any closer to 
finding help for you. 

By focusing on chips specific causes to the RE problem implies that you have 
ruled out all other causes of the RE problems. One way to draw such conclusion 
is having a number of different designs differing only in the LVDS drivers chip 
being used. All other aspects such as circuit design, PCB layouts, peripheral 
connections, enclosures, environments, etc. are all significantly the same or 
identical. Thus the only variable is the LVDS drivers. Only then could we be 
blaming the chip and looking for chip specific causes. Otherwise you may risk 
chasing the wrong tail. 

It's worth stating my favorite statement about debugging: if one made the wrong 
assumption, one may never find the problem, so when you are facing a dead end, 
re-examine your assumptions. The most famous example is the software bug that 
causes the computer not to boot is an unplugged power cord:) 

I apologize if I am merely repeating everything you already know very well. 
Again, wrong assumption leads to dead end and that helps nobody. 

Best of luck debugging. 

Sincerely 
Alfred 



On October 14, 2016 3:17:26 PM PDT, John Woodgate <jmw1...@btinternet.com 
<mailto:jmw1...@btinternet.com> > wrote:

The ICs themselves are too small to produce significant RE. The RE comes from 
the PCB tracks and external cables. But of course you know that.

 

With best wishes DESIGN IT IN! OOO – Own Opinions Only

 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and 
Associates Rayleigh England

 

Sylvae in aeternum manent.

 

From: MARINA PEYZNER [mailto:epeyz...@sbcglobal.net] 
Sent: Friday, October 14, 2016 10:25 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: Re: [PSES] RE from Flat Panel ICs

 

 

Actually, my question was about Flat panel driver ICs, particularly about chips 
Intersil Techwell TW8804 and National Semiconductor DS90C385A. I had hope that 
somebody has valuable experience with this problem.

 

Thank you anyway,

Eugene 

 

 

 

 

 

 

 

 

 

 

 

On Friday, October 14, 2016 2:12 PM, alfred1520list <alfred1520l...@gmail.com 
<mailto:alfred1520l...@gmail.com> > wrote:

 

And general recommendation! s also say to reduce common mode current. But 
obviously this shouldn't have been said too:)

On October 14, 2016 9:24:36 AM PDT, John Woodgate <jmw1...@btinternet.com 
<mailto:jmw1...@btinternet.com> > wrote:

It seems to me that claiming familiarity with general recommendations severely 
restricts what anyone can add. The general recomm! endation for reducing RE is 
to minimise the areas of current loops by pairing 'go' and 'return' conductors 
on adjacent layers of the PC board. But you obviously know that already.

 

With best wishes DESIGN IT IN! OOO – Own Opinions Only

 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and 
Associates Rayleigh England

 

Sylvae in aeternum manent.

 

From: MARINA PEYZNER [mailto:epeyz...@sbcglobal.net] 
Sent: Friday, October 14, 2016 5:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: [PSES] RE from Flat Panel ICs

 

  

Dear experts,

Flat panel driver ICs are known for their high emission. I have some problems 
with radiated emissions particularly from chips Intersil Techwell TW8804 and 
National Semiconductor DS90C385A.

Could you, please share your knowledge about reducing this RE. We are familiar 
with general recommendations.

 

Thank you,

Eugene 

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