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I have a heating control application for which I would like a stable clock that reliably starts for 20 years under conditions of varying temperature and humidity. The board will be properly designed with very short leads from the processor to the crystal.

Question asked by John Romanowich on Dec 22, 2016

I have a heating control application for which I would like a stable clock that reliably starts for 20 years under conditions of varying temperature and humidity. The board will be properly designed with very short leads from the processor to the crystal.  I reviewed Freescale app note AN2606 and was hoping that you could share what 32.768kHz Crystal and circuitry would be best to achieve the most stable result.  If it is best to use a high frequency crystal in the 10Mhz range to achieve the best long term stable performance, than that is what I will do.

 

 We are currently developing a product using a Freescale S9KEAZN64AMLC and we wanted to a very stable design.  Assuming you feel a low frequency crystal is a good candidate for this application, do you know if an Abracon ABS25-32.768KHZ crystal would be a good choice?  Do you think it is ok to use the S9KEAZN64AMLC in low frequency low power mode or do you think it would be more stable in the higher power mode using the external components? 

 

I don’t need extreme accuracy, I’m just concerned about the processor always starting so there are not issue in the field.  Or if noise could hang up the processor if in low power mode.  Thanks for any guidance you could provide. 

 

John

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