[SI-LIST] Re: Why Thumb rule 40 mils takes 1A
- From: "Husainee Plumber" <husainee.plumber@xxxxxxxxxxxxxxxxx>
- To: "Vijay Anand" <vijayanand.ganesan@xxxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 7 Dec 2010 18:02:41 +0530
As per PoE standard the max wattage is 15.4W per port (not PoE+) which
means for 48V , max current should be 320mA. Why are you loading 1A.
The trace width required to carry current depends on the following
- layer of routing (inner or outer)
- copper thickness of trace
- maximum temp rise the board can withstand
1A/40mils could be a good approximation for 7-10degree temp rise/1oz of
copper/inner layer track
There are many track width calculators available on the net which can
give fairly good approximation of current carrying capacity of traces.
Regards
husainee
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Vijay Anand
Sent: Tuesday, December 07, 2010 5:48 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Why Thumb rule 40 mils takes 1A
Dear All,
I have a Giga POE signals which is routed on 4 width, 5.5 space and 1.8
mil
thickness. I have loaded up to 1A in that lines. Initially I thought
the
track will damage (since the thumb rules says 40 mils takes 1A) but it
didn't happen the way I thought. My doubt is what is the actual
current
carrying capacity for 40 mil and 4 mil? Is there is any rule on the
track
width for the PHY signals which has POE.
Please share your experience.
Thanks and Regards,
Vijay
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