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Winfield Hill
Guest
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 Posted:
Mon Oct 03, 2005 12:35 am Post subject:
Re: Divide by N chip |
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TRABEM wrote...
| Quote: |
I think I've found a source for inexpensive 12.8 Mhz TCXO's ...
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That could be *very* helpful in a project I'm working on,
where'd you find those 12.8 Mhz TCXOs?
--
Thanks,
- Win
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Guest
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| Posted:
Mon Oct 03, 2005 7:47 am Post subject:
Re: Divide by N chip |
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TRABEM wrote:
| Quote: | There is good news. By tightening up some other parts specs, I was
able to get the minimum usable clock frequency down to 12.8 Mhz. This
allows a TCXO similar to those used in cell phones to be used...which
makes it even easier to implement with high stability.
By the way, Phillips has sold their digital chip division to TI and
the Phillips digital cmos parts are slowly disappearing from the
market as the remaining stock is sold by distributors.
I did a spot check however, and the HCT and the HC parts are made by
TI now, which is good news. In fact, TI is distributing the Phillips
PDF's through their website....so it appears the Phillips parts will
live on, at least for awhile longer.
I think I've found a source for inexpensive 12.8 Mhz TCXO's, so it
looks like I'll use them with a couple of AND gates to get my divided
down LF and VLF frequencies.
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If you can make do with 8 stages (rather than 16) for your LO
frequency,
you may use the HC40103, which fits into a 16-pin package. It is more
readily available and cheaper (about USD 0.50) than the HC4059 while
the
speed is the same (SGS-Thomson state a maximum clock rate of 40MHz typ
at 5V - no temperature specified).
Note that standard AT-cut crystals in a HC-49U package have temperature
coefficients of typically -0.5ppm/K around room temperature - that's
only 50mHz/K at 100kHz. (Cell-phone frequencies are another matter.)
Martin. |
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Anton Erasmus
Guest
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| Posted:
Wed Oct 26, 2005 10:10 pm Post subject:
Re: Divide by N chip |
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On 26 Sep 2005 10:58:48 -0700, clicliclic@freenet.de wrote:
| Quote: |
TRABEM wrote:
Hi all,
I need a divide by N chip, covering a divide range of 20 to 300 or so.
I know I can build it with a binary counter and an 8 input nand gate.
But, I'd like to have it all in one chip if possible.
They used to make these things for phase locked loop building blocks,
but I don't see anything like that listed in the Mouser catalog...so I
need some suggested vendors and part numbers that might be
appropriate.
It would be nice if it had a crystal oscillator built in or perhaps
just a crystal input. But, a plain ole divider would meet my needs and
I could do my own oscillator.
If it covers a larger range of N values, that's ok too.
Any suggestions? Who makes these things today?
Thanks,
T
The 4059 (CD4059, HEF4059) is still available at some places, for
about USD 3.00. To make it run at 15MHz, it requires a higher supply
voltage of 10V to 15V, though.
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The 74HC4059 or 74HCT4059 can go up to 40MHz at 5V. They are
available from Philips and probaly other manufacturers such as
Fairchild and TI as well.
Regards
Anton Erasmus
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