Programmable clock divide-by-N

T

Thomas Magma

Guest
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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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
Click to expand...
Not SC70 but the On Semiconductor Fxxxx chips are really nice to use with
two-wire variants available.

- --
Brendan Gillatt | GPG Key: 0xBF6A0D94
brendan {a} brendangillatt (dot) co (dot) uk
http://www.brendangillatt.co.uk
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Not SC70 but the On Semiconductor Fxxxx chips are really nice to use with
two-wire variants available.
Click to expand...
Thanks Brendan, could you elaborate on what series the Fxxxx is? I'm having
a hard time finding it.

Thomas
 
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
Click to expand...
Is the 54/74HC4059 any good to you?
 
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Hash: SHA1

Thomas Magma wrote:
Not SC70 but the On Semiconductor Fxxxx chips are really nice to use with
two-wire variants available.


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

Thomas
Click to expand...
Woops, make that FSxxxx series!

http://www.onsemi.com/PowerSolutions/parametrics.do?id=125


- --
Brendan Gillatt | GPG Key: 0xBF6A0D94
brendan {a} brendangillatt (dot) co (dot) uk
http://www.brendangillatt.co.uk
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On Dec 18, 3:47 pm, "Thomas Magma" <somewh...@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).
Click to expand...
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...
 
"pimpom" <pimpom@invalid.invalid> wrote in message
news:hghphe$cnu$1@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?
Click to expand...
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
 
On 2009-12-21, Thomas Magma <somewhere@overtherainbow.com> wrote:
"pimpom" <pimpom@invalid.invalid> wrote in message
news:hghphe$cnu$1@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.
Click to expand...
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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