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Date:	Mon, 10 Feb 2014 12:59:58 -0500
From:	Dave McGuire <mcguire AT neurotica DOT com>
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To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] How to identify nc pads in tsym files
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On 02/10/2014 11:11 AM, Frank Miles wrote:
>> I'm dealing with a QFN16 package where the middle "pin" is used as a
>> signal. The only way to get to the middle pin is a via (not sure this
>> is a good idea...), or I can trivially use an nc pin on the package to
>> get to the center.
> 
> You have to be careful about 'NC' pins.  Sometimes these are truly not
> connected; but for some chips these are connected to internals in ways
> not fully revealed in the datasheet - so the pin is more of a "don't YOU
> connect to this" than a truly "Not connected (anywhere)".

  I got screwed by exactly this a few weeks ago, with a 4-20mA pressure
sensor.  The assembly guys wired the harnesses with the "NC" wire
connected to ground.  The sensors just plain DID NOT WORK in that
configuration.  I had 'em clip and terminate that wire, and they all
came up just fine.

                  -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA

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