[SI-LIST] Re: Common-mode noise on LVD Drivers
- From: Raymond.Leung@xxxxxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 30 Mar 2004 10:24:10 +1000
I would say this is an I/O design problem because the package
behavior has not been modelled well in the output driver design
phase. By the way, not all I/O designs are equal. Some of them
may intrinsically have more common mode noise than others;
and faster technology does not necessarily incur more noise.
On the other hand a fast technology may even provide more
room to tune the I/O circuit to reduce the CM noise.
Regards,
Raymond
"Lee Ritchey" <leeritchey@xxxxxxxxxxxxx> on 30/03/2004 07:48:39
Please respond to leeritchey@xxxxxxxxxxxxx
To: "Ravinder.Ajmani@xxxxxxxx" <Ravinder.Ajmani@xxxxxxxx>,
si-list@xxxxxxxxxxxxx
cc: (bcc: Raymond Leung/sdc)
Subject: [SI-LIST] Re: Common-mode noise on LVD Drivers
Ravinder,
There are a couple of ASIC suppliers who have package design problems that
lead to common mode problems in the form of Vcc and ground bounce. If you
have one of those, there is nothing you can do at the board level to fix
the problem.
Lee
> [Original Message]
> From: <Ravinder.Ajmani@xxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 3/29/2004 9:13:16 AM
> Subject: [SI-LIST] Common-mode noise on LVD Drivers
>
> Hi All,
> There was a thread some time back about differential to common-mode
> conversion. My problem is also in this area. I have two similar ASICs
> with multiple LVD drivers. On one ASIC, I measure common-mode noise
about
> 20 dB higher than the other. Even within this ASIC, some bits show about
> 6 dB more common-mode compared to the quietest bits. The two ASICs are
> from different vendors, and the one with higher CM noise uses faster 11
uM
> technology. I don't know the technology of the other ASIC, but its die
> size is considerably larger. This high common-mode noise is causing EMI
> problem, which I am trying to fix. I have tried changes in the card
> decoupling scheme but it does not make any difference. I am convinced
> that the common-mode noise is coming out of the ASIC, and the PCB
> improvements may not help. Is there any way to come to a definite
> conclusion about this, and is there anything I can do besides placing
> common-mode ferrite beads on every driver pair.
> The ASIC uses a core voltage of 1.8V, and has on-board regulators to
> regulate 3.3V input to 1.8V.
> I will really appreciate your help in solving this puzzle.
> Regards, Ravinder
> Server PCB Development
> Hitachi Global Storage Technologies
>
> Email: Ravinder.Ajmani@xxxxxxxx
>
> ------------------------------------------------------------------
> 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:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
> List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl
>
> List technical documents are available at:
> http://www.si-list.org
>
> List archives are viewable at:
> //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:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//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:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//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:
