[SI-LIST] Re: Stack up for EMI reduction,plane resonance and u-str ipradiation etc etc
- From: "Vishram Pandit" <vishrampandit@xxxxxxxxxxx>
- To: marangyi@xxxxxxxxxxx, zhang_kun@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Mon, 16 Feb 2004 23:27:06 +0000
HI Roy,
The Stack up I was referring to has second layer Ground and fifth layer
power(split) for a six layer board. Or second layer ground and seventh layer
power (split) for an eight layer board. All other layers have signals
routed.
Thanks,
Vishram
>From: "Ron Matthews" >Reply-To: marangyi@xxxxxxxxxxx >To: , , >Subject:
[SI-LIST] Re: Stack up for EMI reduction,plane resonance and u-str ip
radiation etc etc >Date: Mon, 16 Feb 2004 15:18:35 -0500 >>Hi Vishram,
>>Could you please elaborate a little more on the stackup you >referred to
inyour message below? >>Thanks! >>Best regards, >>Ron Matthews
>President/Principal Consultant >Noise Doctors, Inc. >rfm@xxxxxxxxxxxxxxxx
>Voice: 508-251-1224 >Cell: 978-857-7634 >Fax: 508-861-0536
>>>>-----Original Message----- >From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] >On Behalf Of Vishram Pandit >Sent:
Sunday, February 15, 2004 10:27 PM >To: zhang_kun@xxxxxxxxxx;
si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] Re: Stack up for EMI
reduction,plane resonance and >u-str ip radiation etc etc >>>Zhangkun, >>I
have a comment on b, You mention: >>>"b)I have done some measurement. No
matter have many caps are placed on >the >boards, the impedance of PDS
beyond200MHz will not get better. It >should be >clarified that now I do not
use cap less than 1000pF." >>It depends on your stack up. If you have power
and ground plane adjacent >to >each other, this may be true. But if you have
say 6 or 8 layer stack up >with >second layer ground and last but one layer
power, then you can use lower >value caps to reduce the impedance of the
power and ground at higher >frequencies (>200MHz). I have used caps as low
as100pF to reduce the >impedance between P/G. With say 1-2nH via inductance,
the effect of the >caps is very local, but several of the caps can be placed
strategically >at >hot spots. It immensely helps alleviate EMI. >>Thanks,
>>Vishram >>>From: Zhangkun >Reply-To: zhang_kun@xxxxxxxxxx >To:
>si-list@xxxxxxxxxxxxx >>Subject: [SI-LIST] Re: Stack up for EMI
reduction,plane resonance and >u-str >ip radiation etc etc >Date: Fri, 13
Feb2004 09:42:15 +0800 >>Dear all: >>>I >have reviewed the mails in this
thread. The following is my points. >>>a)From >my view, I am caring about
theEMI of PCB. Very small common mode noise >will >give rise to critical EMI
problem. In my experience, the common mode >noise >isproportional to the
impedance of power delivery systems. This has been >verified by measurement
and simualtion. >>b)I have done some >measurement. No >matter have many caps
are placed on the boards, the impedance of PDS >beyond >200MHz will not get
better. It should be clarified that now I do not use >cap >less than 1000pF.
When the caps less than 1000pF is used, there will be >a >lotof
antiresonance. This is also verified by simualtion and >measurement. >>>c)I
have not studied the interaction between signal in trace and noise >in
>plane. However, I have treated one case, in which the noise in plane
>seriously affect the signal in trace. After we eliminate the noise in
>plane, >the signal become very good. >>Best Regards >>Zhangkun >2004.2.13
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