[SI-LIST] FW: FW: Re: HIGH DC Current on GND Plane
- From: "Shimko, Steven R." <s.shimko@xxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 19 Jun 2007 13:28:20 -0400
Lee-
I stand corrected. I misread the pwb stackup spreadsheet. Layer count
is 34 as a write this, with a mixture of 2 oz, 1 oz, and 0.5 oz layers
(no 4 oz). 20 of the layers are 1 or 2 oz copper.
Steve
-----Original Message-----
From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx]=20
Sent: Tuesday, June 19, 2007 12:05 PM
To: Shimko, Steven R.; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] FW: Re: HIGH DC Current on GND Plane
Wow! Why 4 ounce power planes? Must drive your fabricator nuts trying
to etch and laminate such thick copper.
Lee Ritchey
> [Original Message]
> From: Shimko, Steven R. <s.shimko@xxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 6/19/2007 4:39:18 AM
> Subject: [SI-LIST] FW: Re: HIGH DC Current on GND Plane
>
> Eddy-
>
> I am working on a low voltage (1.5V) system that needs to distribute=20
> over 100 amps of current across 4 backplanes with less then 1% loss. =20
> I am not the power system designer, but I have high speed digital=20
> signals that need to go over those same backplanes, so am familiar=20
> with the issues. The most recent configuration for the PWB is a 30+=20
> layer stackup with several 4 oz copper layers. So it can, and is=20
> done. Just takes copper!
>
> Steve Shimko
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx=20
> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of steve weir
> Sent: Tuesday, June 19, 2007 1:40 AM
> To: eddyvk@xxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: HIGH DC Current on GND Plane
>
> Eddy, think telecom backplane. Big iron boxes today support 2-3kW.=20
> =3D20 With a -48V supply that still adds up to 40-60 amps or even =
more.
>
> Steve.
>
> Eddy wrote:
> > "Saturation at DC is spelled meltdown" ROTFLMAO
> >
> > 60 Amps is an awful lot. That's like the current required to start=20
> > a=3D20 good size car! My first thought was "that has got be noisy as =
> > hell!".=3D20 Theoretically the DC current should not cross-talk=20
> > anything into your=3D20 signal lines but I have a very hard time=20
> > believing that 60 Amps of=3D20 current can be quiet enough.
> > However, I have seen Amps being confused with milli-Amps before....=20
> > =3D20 60 Amps is unrealistic to be flowing through a PCB. The copper =
> > would=3D20 be curling off the FR4. There has to be a typo here
somewhere....
> >
> > Eddy
> >
> > --- "Townsend, Fred" <ftownsend@xxxxxxxxxxxx> wrote:
> > =3D20
> >> I don't know the parties involved here but I think I would =
start=3D20
> >> analysis with psychoanalysis. It would take a lot of convincing=20
> >> for=3D20 me to buy into this methodology. You don't say if the 60=20
> >> Amps is=3D20 static but if it changes there will certainly by cross
talk!
> >> Can you say ground
> >> bounce? Normally one would want such current on the outside of=20
> >> the=3D20 board where I would be looking for 4oz copper if your =
vendor
> >> can=3D20 supply it.
> >> Saturation at DC is spelled meltdown. Have you done temperature=20
> >> rise=3D20 analysis?=3D3D20
> >>
> >> The only good news about this design I can see is iron=20
> >> magnetically=3D20 saturates. Air and epoxy doesn't.
> >>
> >> Fred Townsend
> >>
> >>
> >> -----Original Message-----
> >> From: si-list-bounce@xxxxxxxxxxxxx
> >> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> >> On Behalf Of Joe Paul M
> >> Sent: Saturday, June 16, 2007 3:07 AM
> >> To: si-list
> >> Subject: [SI-LIST] HIGH DC Current on GND Plane
> >>
> >>
> >>
> >> I have a midplane carrying 60Amps of current and Same GND plane=20
> >> is=3D20 used=3D3D20 as reference for multiple of 6.6 Ghz serdes =
lines ,
> >> PCI-e=3D20 lines and GE lines Is there anything similar to=20
> >> 'saturation' in=3D20 Inductors applicable to GND
> >>
> >> plane?
> >> ( Due to saturation of flux in the flux carrying medium , beyond =
=3D
> a=3D3D20
>
> >> certain amount of DC current inductors saturate and wont act=20
> >> as=3D3D20=3D20 inductors for any AC superimposed on the DC. ) Will=20
> >> cross talk=3D20 increase due to the absence of mutual inductance=20
> >> between
> >>
> >> signals and gnd plane ?
> >> Is there anything else that can go wrong due to this DC , AC=3D20=20
> >> current=3D3D20 mixing in planes ??
> >> =3D20
> >
> >
> >
> > =3D20
> >
> ______________________________________________________________________
> __
> ____________
> > Looking for earth-friendly autos?=3D20 Browse Top Cars by "Green=20
> > Rating" at Yahoo! Autos' Green Center.
> > http://autos.yahoo.com/green_center/
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