[SI-LIST] Re: Etch resistors

  • From: steve weir <weirsp@xxxxxxxxxx>
  • To: chris_landrum@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
  • Date: Fri, 19 Mar 2004 06:30:41 -0800

Chris, Key already addressed the inductance issue, and you have addressed 
the accuracy and temperature issues.  The other three things that you might 
want to watch out for:

1) If it is a surface structure, plating accuracy,
2) If it is a surface structure, thermocouple effects
3) Area

I would model the little beast over your environment and see if it 
plays.  Assuming this is in half ounce etch, then the length will be about 
40X the width.  It is going to have to be pretty big to get the L/R much 
below 1uS.  Thinner but wider etch ( bigger structure ) will help.

Regards,


Steve.

At 05:35 AM 3/19/2004 -0800, Landrum, Chris wrote:
>I would like to use a 20-50 mOhm etch resistor in a power supply circuit on
>a board that I am working on.  The PCB manufacturer is actually VERY
>accurate when it comes to forming these etch resistors in etch.  The etch
>resistor will save a bundle of $ compared to the mOhm range power resistors
>(high volume product).  I will obviously be sizing the etch for the current
>demand, and I will be considering heating of the etch.  Can anyone think of
>any reason that I would NOT want to do this?  A reason that I am not
>considering perhaps?
>Thanks.
>Chris
>
>
>
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