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From: whit3rd on 20 Dec 2009 21:18
On Dec 18, 3:47 pm, "Thomas Magma" <somewh...(a)overtherainbow.com>
wrote:
> 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).

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 = 833 kHz,
and put a small capacitor from the fast clock to the threshold pin...

From: Thomas Magma on 21 Dec 2009 11:46

"pimpom" <pimpom(a)invalid.invalid> wrote in message
news:hghphe$cnu$1(a)news.albasani.net...
> Thomas Magma wrote:
>> 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
>
> Is the 54/74HC4059 any good to you?
>

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


From: Jasen Betts on 23 Dec 2009 06:19
On 2009-12-21, Thomas Magma <somewhere(a)overtherainbow.com> wrote:
>
> "pimpom" <pimpom(a)invalid.invalid> wrote in message
> news:hghphe$cnu$1(a)news.albasani.net...
>> Thomas Magma wrote:
>>> 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
>>
>> Is the 54/74HC4059 any good to you?
>>
>
> 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.

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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