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Re: [Paparazzi-devel] Tiny13 3V3 Rail Problem (11 ohms)

From: Matthew Currie
Subject: Re: [Paparazzi-devel] Tiny13 3V3 Rail Problem (11 ohms)
Date: Sun, 14 Oct 2007 19:07:02 -0700
User-agent: Thunderbird (Windows/20070728)


  I began systematically removing components that sat directly on the 3V3 line and it wasn't until I removed the LPC2148 that I got > 2Mohm on the 3V3 line.  I now figure it was the IC or the solder connections under/around it.  I will add another LPC tomorrow and see where I am.  Thanks for the shot.

Matthew Currie

address@hidden wrote:
Matt, the only component that will have trouble with 17V is the big tantalum input cap on the 5V line.  If this is damaged, you will have noisy 5V or a battery short.  The 1117 will repeatedly turn on/off when the 3V bus is shorted - I've seen this happen with bad gps soldering or external shorts.  Maybe the noisy 5V line killed some of the 3V caps? 

-- Matthew Currie <address@hidden> wrote:

 I have a Tiny13 here which was operating happily during the day and
upon returning the next, it was not.  I was powering it with ~ 17V
inadvertently which may be relevant to the problem.  The symptoms I
observed were the 3V3 line coming on briefly and then dropping out,
pulsing about once per second or so.  I removed the LM1117 regulator IC
and now measure 11 ohms across the GND and 3V3 rail.  Before I begin
tearing components off I wanted to run this past others in case they
came across something similar.  I can't picture what would be causing 11
ohms of conductance across the rail.  In summary, it ran for almost 24
hours at a high voltage (17V) so if something burnt up, this would
explain it.

Matthew Currie

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