RE: [SI-LIST] : Power Planes

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From: Heard, Chris (cheard@cereva.com)
Date: Thu Oct 05 2000 - 05:52:42 PDT


David,
 
At 3.3v, you'll have 40Amps. I'd be comfortable with two 1 oz copper planes
for this voltage (two 1oz planes for gnd also). 1.2W/sq inch is alot and
will come down to package specifics. Large ceramic BGAs with a 0.8C/Watt
Theta JC will be a much better choice than small pqfp packages with 9C/Watt.
Time to start considering impellers to move air if you're worried about
operation during a failure too. 20A over a 10"x10" board on a single plane
isn't much...
 
Regards,
Chris

-----Original Message-----
From: Chen, David [mailto:dchen@corvis.com]
Sent: Thursday, October 05, 2000 8:47 AM
To: Si-List (E-mail)
Subject: [SI-LIST] : Power Planes

Dear SI List,

I ran across this list accidentally, and am glad I did. Lots of interesting
stuff that is applicable to what I am doing.

I am in the early stages of designing a board with lots of power. One supply
voltage needs to support up to 130Watts on a board about 105 square inches.
Besides heat problems, will the large currents require special power plane
considerations, like heavier copper weight, heavier ground plane, etc. What
is the current carrying limit of 1 oz copper planes? Will the large currents
affect signal trace impedances?

Thank you,
  Dave Chen

*
* David K Chen
* dchen@corvis.com
* Corvis Corp./Baylight Networks Division
* www.corvis.com
*

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