[SI-LIST] 答复: power planes (4-layer-board)

Hi Daniel

I agree with the option of David's from the view of EMC.

1)If the PCB is of 4-layered, the product would not be high-end product. There 
is no a lot of strict power request. The power trace would be enough.

2)According to my experience, the power-ground plane pair in 4-layer PCB would 
be bad for EMC. We have done the contrast experiment. The RE difference is 
about 10db.

Hope this would be helpful

Best Regards

Zhangkun
2009.2.16


张坤
华为技术有限公司  huawei_logo


地址：深圳市龙岗区坂田华为基地 邮编：518129
http://www.huawei.com
-------------------------------------------------------------------------------------------------------------------------------------
本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁
止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中
的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！
This e-mail and its attachments contain confidential information from HUAWEI, 
which 
is intended only for the person or entity whose address is listed above. Any 
use of the 
information contained herein in any way (including, but not limited to, total 
or partial 
disclosure, reproduction, or dissemination) by persons other than the intended 
recipient(s) is prohibited. If you receive this e-mail in error, please notify 
the sender by 
phone or email immediately and delete it!


-----邮件原件-----
发件人: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] 代表 
Daniel Bauer
发送时间: 2009年2月14日 20:38
收件人: si-list@xxxxxxxxxxxxx
主题: [SI-LIST] power planes (4-layer-board)

Hi, 

the standard layout for an 4-layer PCB is, using outer layers for the signals 
and the two inner layers for one ground and one power plane. The power plane 
seems to have a few advantages as well as disadvantages (using an 4-layer 
board). 

If a trace running at the top layer has to change to the bottom layer - also 
the return current has to change the layer (using stitched capacitors). 

What do you think about the proposal to use the third layer for ground as well 
as for power? On every position where an signal trace is running at the bottom 
layer, the third layer will be a ground plane, connected to the ground plane on 
the second layer.... and when there`s no trace on the bottom layer I will use 
an power plane on the third layer.  From this it follows that I will get some 
power islands on the third layer which were connected with traces on the bottom 
or top layer.  The complete return current should use the ground plane (which 
has an lower impedance) and not one of the small power islands. 

Would there be an impedance change for the signal traces changing the layer 
(top to bottom or vica versa) when both inner layers will use an ground plane 
where the signal is running? 


x----------|                      (top layer - signal layer)
    GND   |   GND            (second layer is a complete ground plane)
Power    |   GND            (ground and power islands)
              |---------x         (bottom layer - signal layer)

The line will show a signal trace changing from the top to the bottom layer. 
Both ground planes using at the inner layers, will be connected together by 
many vias. Could you tell me if this would be a good decision improving signal 
integrity? Are there any kind of disadvantages?


best regards
Daniel  
    


____________________________________________________________________
Psssst! Schon vom neuen WEB.DE MultiMessenger gehört? 
Der kann`s mit allen: http://www.produkte.web.de/messenger/?did=3123

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: