[time-nuts] frequency sources

Hal Murray hmurray at megapathdsl.net
Fri Oct 16 03:43:55 UTC 2009

> I'm not familiar with that particular part, but it's something to be
> aware of.

Your choice of output frequencies is pretty limited.

Overview (with diagram and link to full data sheet) at:

It's got an internal oscillator.  You have a choice of 133, 125, 120, 100 or 
66 MHz.  (by ordering the right part number)

One output is that osc, possibly divided by 2, 4, or 8.

The second output is the same osc that goes through or around 2 dividers.
  The first is 2, 4, or 8.  The second divides by 2 through 1025.

It's not clear that you can control the output frequency well enough just by 
changing the temperature.  The graph is on page 20 of the data sheet.  (next 
to last page)  I'm sure the output frequency will change if you adjust the 
temperature, it's just not clear (to me) that you can steer it to a value of 
your choice.

The typicals graph shows 1/4% over temp.  The specs say 1/2% at 25C and 70C, 
1.4% from +25 to +85C, and 1% for supply voltage.

But it's a dome shaped curve.  You want a ramp.

You might be able to make it work if the output frequency you want allows you 
enough flexibility in picking the divider.  Say you want 1 MHz.  So pick a 
133 MHz part, and divide by 133 or 132 or 134, depending on how the part you 
get actually ticks.

These are my opinions, not necessarily my employer's.  I hate spam.

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