RE: [SI-LIST] : Capacitor dielectric type

About this list Date view Thread view Subject view Author view

From: Mark Gill (gillmf@nortelnetworks.com)
Date: Wed Dec 06 2000 - 11:10:18 PST


Hey Mike -
 
Decoupling the backplane is not required if the boards are correctly
filtered/decoupled. None of the systems I have worked on require decaps on
the backplane (reliability problem), and none of them have ever exhibited
this type of problem. But we do have good filtering/decoupling on the -48 V
input to each card. Smart powering (which Joseph mentions) is a slicker
approach, and very reasonable when considering switching power systems. But
depending on the actual parasitics (inductances, resistances, and
capacitances), you certainly can get high frequency ringing upon insertion -
try simulating with SPICE to get a feel. The toughest parasitic should be
the inductance. There are some ferrites which offer good resistive losses
at higher frequencies. I would still call this an inrush phenomenon.
 
Mark

-----Original Message-----
From: Michael Nudelman [mailto:mnudelman@tellium.com]
Sent: Wednesday, December 06, 2000 12:54 PM
To: Gill, Mark [NCRTP:9030:EXCH]
Cc: 'Dennis Schmitz'; si-list
Subject: Re: [SI-LIST] : Capacitor dielectric type

And, yeah - the backplane should be de-coupled as well. The problem is - to
find 48V ceramic SMT caps of significant cacacitance is a pain.

Mike.

Mark Gill wrote:

Dennis -Your board insertion problem sounds more like an in-rush current
problem than power plane resonance. Do you have further details which would
confirm resonance over inrush?Mark

-----Original Message-----
From: Dennis Schmitz [ mailto:den@positron.net <mailto:den@positron.net> ]
Sent: Tuesday, December 05, 2000 5:38 PM
To: si-list
Subject: Re: [SI-LIST] : Capacitor dielectric type
 
Can some kind person please point me to some references on power-plane
resonance? I am researching for a new backplane design of an existing system
where we are having some problems with board insertion causing disturbances
on the power distribution planes. Thanks in advance.

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Tue May 08 2001 - 14:30:22 PDT