[SI-LIST] Re: Why"Void power and ground planes under discrete magnetic components"

  • From: <karthikeyavelan.kandasamy@xxxxxxxxx>
  • To: <emcesd@xxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Fri, 23 Dec 2011 05:55:57 +0000

Hi,

Yes , if you use transformer, you need to avoid any plane & signal under the 
transformer.
Because transformer will induce the magnetic  coupling - noise to under any 
signal/ plane/copper.

If you use transformer integrated RJ45, Normally the connector will be 
shielded. so no need to provide the void.
Please look the datasheet of part. Datasheet will have the internal circuit 
also.

Regards
Karthik


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of Tesla
Sent: Friday, December 23, 2011 8:09 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Why"Void power and ground planes under discrete magnetic 
components"

Hi, expert
i recently read a ti doc about ethernet pcb layout. 
http://www.ti.com/lit/an/snla107/snla107.pdf
There was a setence on page 7"Void power and ground planes under discrete 
magnetic components." Can somebody explain why TI recommand to do like that?
Now, we often use tranformer integrated RJ45, how we do about this on the PCB?
Must we create a void on power and ground plane on PCB if there is a 
transformer?(eg,a switch power transformer?)
 
Merry xmas
Thank you
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