Re: ideal trace width for 2A current???

On Fri, 07 Dec 2007 05:39:44 -0800, Ajab wrote:

On Dec 7, 6:29 pm, Stef <stef...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
In comp.arch.embedded,

Ajab <jasusvi...@xxxxxxxxx> wrote:
What is the ideal trace width for 2A current...in a Non Impedance
controlled board layout?
I tried calculating it ..but the values are different... Can anyone
tell me regarding this?

That depends on what ideal means to you!

If you want minimal impedance, than as wide as possible.

If you want to uses as less space as possible, determine the allowable
warm-up of the trace and calculate the minimum width for that.

If...

--
Stef (remove caps, dashes and .invalid from e-mail address to reply
by mail)

Some time back I read 1A requires 1mm of trace. It was not mentioned
internal or external.
Now on board I have space constraint...so at the max I can make it 2mm.
But is it really necessary?
As I mentioned it is Non impedance controlled board. Signals have been
routed in GND and VCC plane. I have to modify this board for 2A.
Previous tracks are of 1mm for 1A current.

If you don't care about how much the voltage drops, or how long the trace
lasts, you can make it as thin as your fabrication house can reliably
etch it.

If not, then what Stef said is valid, and the calculator that Arlet gave
you a link to is (if it's what I think it is) appropriate to give you the
information you need.

Keep in mind that if you've been told to do this, you're probably being
paid to do this: i.e. you're being paid to think. I can't speak for
anyone else directly, but while I'm happy to dispense some knowledge on
newsgroups for free, I generally like to get paid for thinking, too, so I
don't do much actual number-crunching engineering for people on
newsgroups.

So this'll be the third response with knowledge, now it's your job to go
heat up some brain cells.

There are two reasons for making the trace wide: One, because it'll drop
voltage proportional to resistance and current. At high currents, if you
don't want too much voltage drop you'll need to bring the resistance
down. Two, because that voltage drop times that current will cause
resistive heating. At high currents, if you don't want the trace burning
off the board then you'll need to bring the resistance down.

There are three factors that you can control: One, you can order the
board made with thicker than normal copper, so that each trace, for a
given width, has less resistance per unit length. Two, you can make the
trace wider, which both decreases the resistance per unit length and
increases the ability of the trace to dissipate heat. Three, you can
have bare wires soldered on top of the traces, or you can replace the
traces with insulated jumpers (I wouldn't do this unless I were
desperate, but you never know).

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
.

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