[SI-LIST] FW: Re: HIGH DC Current on GND Plane
- From: "Shimko, Steven R." <s.shimko@xxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 19 Jun 2007 07:09:00 -0400
Eddy-
I am working on a low voltage (1.5V) system that needs to distribute
over 100 amps of current across 4 backplanes with less then 1% loss. I
am not the power system designer, but I have high speed digital signals
that need to go over those same backplanes, so am familiar with the
issues. The most recent configuration for the PWB is a 30+ layer
stackup with several 4 oz copper layers. So it can, and is done. Just
takes copper!
Steve Shimko
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [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
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 a=20
> good size car! My first thought was "that has got be noisy as hell!".=20
> Theoretically the DC current should not cross-talk anything into your=20
> signal lines but I have a very hard time believing that 60 Amps of=20
> current can be quiet enough.
> However, I have seen Amps being confused with milli-Amps before.... =20
> 60 Amps is unrealistic to be flowing through a PCB. The copper would=20
> be curling off the FR4. There has to be a typo here somewhere....
>
> Eddy
>
> --- "Townsend, Fred" <ftownsend@xxxxxxxxxxxx> wrote:
> =20
>> I don't know the parties involved here but I think I would start=20
>> analysis with psychoanalysis. It would take a lot of convincing for=20
>> me to buy into this methodology. You don't say if the 60 Amps is=20
>> 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 the=20
>> board where I would be looking for 4oz copper if your vendor can=20
>> supply it.
>> Saturation at DC is spelled meltdown. Have you done temperature rise=20
>> analysis?=3D20
>>
>> The only good news about this design I can see is iron magnetically=20
>> 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 is=20
>> used=3D20 as reference for multiple of 6.6 Ghz serdes lines , PCI-e=20
>> lines and GE lines Is there anything similar to 'saturation' in=20
>> Inductors applicable to GND
>>
>> plane?
>> ( Due to saturation of flux in the flux carrying medium , beyond =
a=3D20
>> certain amount of DC current inductors saturate and wont act as=3D20=20
>> inductors for any AC superimposed on the DC. ) Will cross talk=20
>> increase due to the absence of mutual inductance between
>>
>> signals and gnd plane ?
>> Is there anything else that can go wrong due to this DC , AC=20
>> current=3D20 mixing in planes ??
>> =20
>
>
>
> =20
>
________________________________________________________________________
____________
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