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

Didier Juges shalimr9 at gmail.com
Sat Nov 2 09:41:11 EDT 2013


The C8051F300 also has a built-in temperature sensor and ADC, so you could
probably implement temperature compensation without any additional
component if needed.


On Sat, Nov 2, 2013 at 8:37 AM, Didier Juges <shalimr9 at gmail.com> wrote:

> 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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