(no subject)

From: Gregory P. Riddick (gr3k@cms.mail.virginia.edu)
Date: Sun May 07 2000 - 11:31:25 EDT

I haven't worked with the ucGardner board(yet), but it
looks like the regulator is standard linear voltage
regulator. Most of these chips have a Zener diode with a
breakdown voltage at their rating(3.3v). Anything more than
3.3v gets shunted to ground, so these little guys can get a
bit warm. Most linear regulators require an input at least
a volt above their rating to accurately deliver their
regulated voltage. If you're nervous, try measuring the
voltage of the output without the ucSimm inserted in your
board. Should be 3.3v, and the regulator may get warm but
definitely not too hot to touch. If it's very hot you've
shorted something, possibly by applying too much
soldering-gun heat to the regulator. To be extra safe
(again without the ucSimm on the board), you can clip a
resistor(33 ohms for a simulated 100ma load,66 ohms for a
50ma load, make sure it's 1/2 watt rated) across the ground
and output of the regulator--make sure not to slip and
short the regulator when you do this). Voltage across the
resistor should stay at 3.3v and the regulator shouldn't
get super hot.

Greg R.

>Okay, I've looked as much as I can look through
>non-searchable mail list
>archives, I checked the documentation, I've searched the
>web, on and on. I'm
>having a bear of a time finding an answer to this (rather
simple) question.
>You'll laugh when you read it...

>I have my uCsimm and uCgardener all set up and ready to
>plug in. I see in the
>manual that this puppy runs at 3.3v. The gardener board
>lists 4-6v (negative
>pin, I believe) near the socket for the power supply's
>plug. Thinking that 4-6v
>was a definitive range for power supplies, I purchased one
>that runs at 4.5v up
>to 700mA.

>Before I plug this thing in, I want to know beyond the
>shadow of a doubt that
>pumping 4.5v into this is okay. This may seem obvious to
>seasoned embedded
>hackers, but some of us are just now starting. When I see
>one set of docs say
>this runs at 3.3v and the board says 4-6v, and there is no
>further explanation
>offered in documentation, the main web site, FAQs, etc., I
>get worried (why
>isn't that clearly documented? I can't be the only person
>who's ever wondered
>about this).


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