[SI-LIST] Re: help: the ground under transformer and common mode choke
- From: steve weir <weirsp@xxxxxxxxxx>
- To: "Zhang, Qing Nan (Qing Nan)" <zhangq@xxxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Fri, 21 May 2004 04:44:07 -0700
Qingnan, no I mean that when the logic ground plane is close to or directly
underneath the isolation magnetics, that it couples to the line side. When
it couples evenly, it impresses CM noise. When it impresses unevenly, it
results in both CM noise and DM distortion.
Regards,
Steve
At 02:29 PM 5/21/2004 +0800, Zhang, Qing Nan (Qing Nan) wrote:
>Steve,
>Thanks.
>I don't understand your second part. Do you mean the noise is come from line
>side ?
>I draw a picture to indicate what I want to do to avoid unwanted noise
>coupling to the signal lines.
>Does this do help ?
>Does this implemented yours' "Voiding logic ground in the vicinity of
>magnetics "?
>
>Best Regards,
>Qingnan
>
> <<...OLE_Obj...>>
>-----Original Message-----
>From: steve weir [mailto:weirsp@xxxxxxxxxx]
>Sent: 2004?5?20? 17:24
>To: zhangq@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: help: the ground under transformer and common mode
>choke
>
>
>The goal is to avoid unbalanced coupling of CM noise from logic ground into
>the line side of the magnetics, not to attempt to isolate logic ground from
>chassis. The latter will create even more noise that you will need to
>isolate from the line side of the magnetics. Voiding logic ground in the
>vicinity of magnetics is one way to reduce the possibility of unequal
>coupling. You should place your magnetics and set your clearances
>accordingly.
>
>Regards,
>
>
>Steve.
>
>At 03:58 PM 5/20/2004 +0800, Zhang, Qing Nan (Qing Nan) wrote:
> >Dear All,
> >We know that the circuit ground and power plane is noisy. Thus we avoid to
> >extend the circuit ground and power plane under the transformer and common
> >mode choke to avoid RF emission.
> >Does it do hlep when we make some holes in the ground plane under the
> >transformers and chokes ?
> >
> >Thanks,
> >Qingnan
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