[time-nuts] How to get 32.768KHz from 10MHz.

Jim Lux James.P.Lux at jpl.nasa.gov
Wed Jul 23 18:22:08 EDT 2008


At 03:01 PM 7/23/2008, Mike S wrote:
>At 05:42 PM 7/23/2008, Bruce Griffiths wrote...
> >Another approach is to divide the 10MHz by 5^7 (78125) and then use an
> >
> >injection locked multiplier chain to generate 32768 Hz from the
> >resultant 128Hz output.
> >It may even be possible to do the 256x multiplication using a single
> >injection locked 32768Hz injection locked multiplier.
>
>You're missing the point. The application is to drive a common, readily
>available consumer clock. Simple and cheap. It can be done with a
>single $1 PIC. You could spend $20 or $100 and not get better results
>for the application. If you can describe a way of doing it for $0.50,
>please do.


But this is time-nuts... Any approach that doesn't have the 
performance of a hydrogen maser or cryogenic sapphire resonator just 
isn't good enough.  Why, we haven't even started on how to build a 
radial ruling engine to make sure the clock face is precisely divided 
into 60 segments to ppb accuracy.

Based on the clocks I've taken apart, dividing the 10MHz down to 1 Hz 
is probably your best bet, rather than trying to hit 32768. However, 
I don't know of a non-programmable single chip solution that will do 
a divide by 1E7. If you want programmable chips, there's countless 
ways, some more elegant than others.











More information about the time-nuts mailing list