Hi dwayne,

I wonder why a pierce oscillator wouldn't work.
You can use an inverter such as
http://www.ti.com/lit/ds/symlink/sn54lvc04a.pdf
which would work as low 1.6V - 3.6V

All you need to do is connect the 32kHz crystal across
the inverter, with damping capacitors and a high value
isolation resistor.

Why wouldn't this work ?

Regards,
Manu


On Thu, Nov 15, 2012 at 4:05 AM, Dwayne Reid <dwayner@planet.eon.net> wrote=
:
> Good day to all.
>
> We are currently trying to help out a customer who has brought us a
> product designed by someone else.  Its based on an Atmel ATmega 328P
> processor and uses a 32KHz crystal for timekeeping.
>
> And - the 32KHz oscillator is not working.  I've messed around with
> it for a couple of days but I can get only 4 out of 7 units
> oscillating by playing around with the crystal caps.  3 units simply
> refuse to oscillate.
>
> I've tried several different crystals, both with 6pF & 12pF
> ratings.  I was able to get 4 of the units working by soldering in
> variable capacitors and fussing with the actual capacitance on both
> sides of the crystal but I am NOT comfortable about the long term
> reliability of the 4 units that are currently working.
>
> A quick Google search reveals that the low-power oscillator mode of
> the 328P is NOT reliable.  Atmel does not have a solution.
>
> So: my thought is to simply glob on an external 32KHz oscillator
> package.  The card runs from 2- "D" cells in series for a operating
> voltage of 1.8V through 3.4Vdc.  This limits my options.
>
> My first grab was for a tried and true part: the Dallas / Maxim
> DS32KHz packaged oscillator.  I've used this part successfully
> several times in the past with great results.  The relatively high
> cost is not much concern right now - I only need to get these 7 units
> working.  Alas, though, the DS32KHz is rated to run down to only
> 2.7V.  That's simply not good enough.
>
> Another thought is to take a small PIC (12f675 comes to mind) and
> glom on the bypass and crystal caps plus the crystal.  It would be
> ugly but would probably work.
>
> Before I go there, though, I thought that see if my fellow PIClisters
> might have a favorite packaged 32KHz module that works over the
> supply range of 1.8V - 3.4Vdc.
>
> Many thanks!
>
> dwayne
>
> --
> Dwayne Reid   <dwayner@planet.eon.net>
> Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
> (780) 489-3199 voice          (780) 487-6397 fax
> www.trinity-electronics.com
> Custom Electronics Design and Manufacturing
>
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