small real time clock crystals

[Jamie Morken]

Hi all,

I am looking for the smallest surface mount real time clock crystal I can
find, digikey has quite a few, ie. the Epson Electronics MC-156 series,
digikey part#:
SE2412CT-ND which is 7.1mm by 3.1mm. Anyone know of a 32.768kHz smt clock
crystal much smaller than this? Also why was 32.768kHz chosen as the
frequency to use for real time clocks?!

cheers,
Jamie Morken

 

[Active8]

On Mon, 22 Mar 2004 06:16:18 GMT, Jamie Morken wrote:

Hi all,

I am looking for the smallest surface mount real time clock crystal I can
find, digikey has quite a few, ie. the Epson Electronics MC-156 series,
digikey part#:
SE2412CT-ND which is 7.1mm by 3.1mm. Anyone know of a 32.768kHz smt clock
crystal much smaller than this? Also why was 32.768kHz chosen as the
frequency to use for real time clocks?!

because log_2(32768) = 15

--
Best Regards,
Mike

 

[John Woodgate]

I read in sci.electronics.design that Active8 <reply2group@ndbbm.net>
wrote (in <e7240tu08yrv$.dlg@news.individual.net&gt about 'small real
time clock crystals', on Mon, 22 Mar 2004:

On Mon, 22 Mar 2004 06:16:18 GMT, Jamie Morken wrote:

Hi all,

I am looking for the smallest surface mount real time clock crystal I can
find, digikey has quite a few, ie. the Epson Electronics MC-156 series,
digikey part#:
SE2412CT-ND which is 7.1mm by 3.1mm. Anyone know of a 32.768kHz smt clock
crystal much smaller than this? Also why was 32.768kHz chosen as the
frequency to use for real time clocks?!

because log_2(32768) = 15

Couldn't you find a more obscure way of telling him? (;-)

Dividing 32768 Hz by 2, fifteen times, gets you 1 Hz pulses. These are
occasionally useful in a clock or watch.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Nemo]

www.microcrystal.ch (I think) is the URL of a Swiss company who make
tiny watch crystals. Really tiny.
--
Paul Honigmann