Programmable clock divide-by-N

Dec 18, 2009 7 Replies
T

For some reason I'm having troubles finding a programmable clock divider chip. I have a 20MHz reference clock that I need divided by 23. I would like the option of changing this divide ratio if needed. I can't seem to find a simple single chip solution (smaller the better). I'm currently looking at CPLDs which is not a clean solution because of ICP. The 40103 is another option but is border line with the max speed vs my operating voltage. I'm also looking at using the R or N counters of a synthesizer chip if this is at all possible.



Seems to me there should be a two wire programmable SC70 divide-by-N available, but I can't seem to find anything close.



Any thoughts?



Thomas


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T

Thanks Brendan, could you elaborate on what series the Fxxxx is? I'm having a hard time finding it.

Thomas

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P

Is the 54/74HC4059 any good to you?

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W

ike

a

Well, if you're not afraid of analog, try a fast '555 variant and pulse-lock it. Free-run oscillate at a little slower speed, say 20/24 MHz =3D 833 kHz, and put a small capacitor from the fast clock to the threshold pin...

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T

I originaly looked at the 4059 but can't find this chip in a fine pitched package, it's too large for the project. I was also hoping for some sort of serial interface so I'm not using up unnecessary pins on my micro.

Thomas

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J

buy a micro with extra counter and use that that'll only use 2 pins (worst case: if you need an output and the

20Mhz input is different from the chip's clock)

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