[time-nuts] 32.768Khz Crystal/Resonator suggestions.

Didier Juges shalimr9 at gmail.com
Sat Nov 2 13:37:39 UTC 2013


I have actually used these chips at 125C and the factory even gave me
extensive data supporting even higher temperature operation (for missile
applications,m can't tell you more). Don't know about 150C though. That is
pretty high.



On Sat, Nov 2, 2013 at 8:36 AM, Didier Juges <shalimr9 at gmail.com> wrote:

> It all depends on how accurate the frequency has to be. If you only need
> 2%, I would use a C8051F300 microcontroller's built-in oscillator (24.5MHz
> +/-2%) and divide it down using the processor itself.
> The chip comes in a 11 pin QFN that is 3x3 mm, a little bigger than you
> need, but it does not require any external component.
> The frequency can be trimmed to better than 2% on many Silabs chips but I
> am not 100% sure that is the case on this one.
>
>
>
> On Fri, Nov 1, 2013 at 11:30 AM, Dan Kemppainen <dan at irtelemetrics.com>wrote:
>
>> Hi all,
>>
>> I've got a project upcoming that will require a frequency of 32.768 Khz
>> in a harsh environment (Imagine a thousand G's at 100Hz with 150 Deg C
>> temperatures). Also, this thing needs to be small, 2mmx1.5x1.5mm or so.
>> It also has to be low power. Frequency stability is probably less of a
>> concern than just surviving (some frequency error vs. temp can be
>> trimmed out with other smarts in the design.
>>
>>
>> In the past, crystals just haven't liked surviving due to the
>> construction. Have had good luck with ceramic resonators at higher
>> frequencies (50Mhz and up). I've also looked at silicon oscillators,
>> which will work in the application, however with the chip and associated
>> resistors/caps they get a little bigger that what I was hoping for.
>>
>> Is anyone aware of a frequency source (crystal/resonator or other) in a
>> small package that is robustly mounted?
>>
>> Or are there any ceramic resonators available that are in small packages
>> in those low frequencies? I checked the big distributors, and did not
>> have any luck.
>>
>>
>> Dan
>>
>>
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>
>



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