[time-nuts] Have 10 MHz need 19.2 MHz
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Sat Jun 15 02:38:30 EDT 2013
I received this all jumbled up in one long line without any sort of
formatting, because the sender's mail client does not use
standardized structure -- so I don't know who wrote what:
>A 74HC4046 can reach 19.2 MHz
Be very careful about specs like that and be sure to read all the
fine print. What can run at that speed? The VCO? The phase
comparator (and which one -- the one you want to use?)? Also, note
that the PC dead zone gets to be a larger and larger percentage of a
cycle as the frequency increases, so the control gets less and less
precise. The 74HCT9046 may be a better choice (no dead zone), but
you may need to select parts to run them at 19+ MHz. No worries,
there are hundreds of fast PLLs out there, but most are more
complicated to apply than the 4046/9046.
>Well some parts whose use is so pervasive, for example, the 2N3904
>and 2N3906 transistor, they will be around *forever* and reasonably
>priced. I believe the MC or LM 1496 falls in this category.
Ten years ago I thought the same about the 2N2222, 2N2907, 2N5179,
2N5109, 2N5320 and 5322, and on, and on, and on, and on.... But they
are all long gone as primary parts. So will be the 1496 before
long. Of course, as long as 2N3904s are available, you can always
build your own 1496 if you're willing to do a bit of selection.
BTW, I see that at least some versions of the ON 1496 are already EOL.
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