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'[EE]: Good prescalers?'
2003\03\02@003021 by Tony Harris

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I'm looking for some recommendations...

I'm looking to sample frequencies for a display - but they are in the range
of 100MHz to 500MHz - much too fast for a PIC, so I'm thinking of using a
prescaler to divide down the frequency.  I'd like something fairly easy to
work with and that has a DIP package available for experimenting, but I'm
really not sure what will work best for me.

Ultimately, I need it divided down far enough where I can use either a
counter, or a PIC input to calculate the input frequency.

any suggestions, and any sample circuitry one might know of that would help
me to integrate such a beast would be most appreciated!!

-Tony

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2003\03\02@023657 by Jinx

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www.embeddedlinks.com/chipdir/f/divider.htm

Also try Googling for "high frequency" + prescaler

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2003\03\02@103101 by Tony Harris

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Thanks.  I keep seeming to loose that website (embeddedlinks), don't know
why.

Have you by any chance used any of the chips?  I was also hoping to get some
input as to which ones (if any) might be easier to implement.

-Tony


----- Original Message -----
From: "Jinx" <joecolquittspamKILLspamCLEAR.NET.NZ>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Sunday, March 02, 2003 1:37 AM
Subject: Re: [EE]: Good prescalers?


> http://www.embeddedlinks.com/chipdir/f/divider.htm
>
> Also try Googling for "high frequency" + prescaler
>

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2003\03\02@161354 by Jinx

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> Have you by any chance used any of the chips?  I was also hoping to
> get some input as to which ones (if any) might be easier to implement

No, sorry, can't help. And the only data on prescalers I have is from
Plessey's 1989 Satellite, Cable and TV IC Handbook (which I got for
the IR section). To take the first divider in the index as an example

SP4632, 1GHz/64. 8 pin, 5V/25mA, Hi-Z input, balanced ECL o/p

o/p = 0.8V p-p min, which I don't know whether is typical or not for
high speed dividers

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2003\03\03@030130 by Roman Black

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Is there any need for a "proper" (ie expensive)
prescaler chip? I thought he asked about using a
PIC to measure freq.

Maybe just use a cheap 8bit counter chip, to give
/128 or /256 of the input signal. The output freq
can be used to clock a PIC timer in ext clock mode
and pulses/period can be used to display freq as
he asked.

A simple fet front end could be added if the input
of the counter chip is not good enough. :o)
-Roman



Jinx wrote:
{Quote hidden}

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2003\03\03@030746 by hael Rigby-Jones

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> -----Original Message-----
> From: Jinx [SMTP:@spam@joecolquittKILLspamspamCLEAR.NET.NZ]
> Sent: Sunday, March 02, 2003 9:14 PM
> To:   KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU
> Subject:      Re: [EE]: Good prescalers?
>
> > Have you by any chance used any of the chips?  I was also hoping to
> > get some input as to which ones (if any) might be easier to implement
>
> No, sorry, can't help. And the only data on prescalers I have is from
> Plessey's 1989 Satellite, Cable and TV IC Handbook (which I got for
> the IR section). To take the first divider in the index as an example
>
> SP4632, 1GHz/64. 8 pin, 5V/25mA, Hi-Z input, balanced ECL o/p
>
> o/p = 0.8V p-p min, which I don't know whether is typical or not for
> high speed dividers
>
ECL (or PECL) or CML levels are normaly used for high speed applications.
0.8v p-p is the standard ECL voltage swing.  Note that plain ECL uses a
negative supply so the actual levels are around -0.8v and -1.6v, and is
therefore a PITA to use in modern circuits.  PECL is the positive supply
equivalent.

Regards

Mike


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2003\03\03@050804 by Jinx

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> Is there any need for a "proper" (ie expensive)
> prescaler chip? I thought he asked about using a
> PIC to measure freq.

500MHz ?

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2003\03\03@060433 by Tony Harris

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> Is there any need for a "proper" (ie expensive)
> prescaler chip? I thought he asked about using a
> PIC to measure freq.
>
> Maybe just use a cheap 8bit counter chip, to give
> /128 or /256 of the input signal. The output freq
> can be used to clock a PIC timer in ext clock mode
> and pulses/period can be used to display freq as
> he asked.

I had thought about that - but the highest counters I can find are around
50MHz (I think I saw a couple of 70MHz, but most were 20MHz or less), which
is too slow for what I'm looking for (100MHz - 500Mhz).  Good idea though -
if you happen to know of a cheap counter that will exceed the 200MHz mark,
that could hold me over for a while until I really need the higher MHz
capability.

-Tony

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2003\03\03@062719 by Spehro Pefhany

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At 05:10 AM 3/3/2003 -0600, you wrote:
> > Is there any need for a "proper" (ie expensive)
> > prescaler chip? I thought he asked about using a
> > PIC to measure freq.
> >
> > Maybe just use a cheap 8bit counter chip, to give
> > /128 or /256 of the input signal. The output freq
> > can be used to clock a PIC timer in ext clock mode
> > and pulses/period can be used to display freq as
> > he asked.
>
>I had thought about that - but the highest counters I can find are around
>50MHz (I think I saw a couple of 70MHz, but most were 20MHz or less), which
>is too slow for what I'm looking for (100MHz - 500Mhz).  Good idea though -
>if you happen to know of a cheap counter that will exceed the 200MHz mark,
>that could hold me over for a while until I really need the higher MHz
>capability.

http://www.fairchildsemi.com/ds/74/74VHC4040.pdf 125MHz guaranteed @5V 12 bits

Here's a single bit one that goes up to 200MHz guaranteed @Vdd=3.3V (max Vdd
is 3.6V). It's still listed as "preliminary", however.

http://www.fairchildsemi.com/ds/NC/NC7SV74.pdf

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spamBeGonespeffspamBeGonespaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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2003\03\03@161256 by Wouter van Ooijen

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> Here's a single bit one that goes up to 200MHz guaranteed @Vdd=3.3V
(max Vdd
is 3.6V). It's still listed as "preliminary", however.

So maybe it is a good match for a 'future product' like the 16F819?

Wouter van Ooijen

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2003\03\03@163954 by Spehro Pefhany

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At 10:11 PM 3/3/2003 +0100, you wrote:
> > Here's a single bit one that goes up to 200MHz guaranteed @Vdd=3.3V
>(max Vdd
>is 3.6V). It's still listed as "preliminary", however.
>
>So maybe it is a good match for a 'future product' like the 16F819?

<ROTFL>  May as well spec some Maxim parts too. ;-)

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
TakeThisOuTspeffEraseMEspamspam_OUTinterlog.com             Info for manufacturers: http://www.trexon.com
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2003\03\04@014154 by Roman Black

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Tony Harris wrote:
>
> > Is there any need for a "proper" (ie expensive)
> > prescaler chip? I thought he asked about using a
> > PIC to measure freq.
> >
> > Maybe just use a cheap 8bit counter chip,
> I had thought about that - but the highest counters I can find are around
> 50MHz (I think I saw a couple of 70MHz, but most were 20MHz or less), which
> is too slow for what I'm looking for (100MHz - 500Mhz).  Good idea though -
> if you happen to know of a cheap counter that will exceed the 200MHz mark,
> that could hold me over for a while until I really need the higher MHz
> capability.


Sorry for that Tony, Jinx already corrected me!
I really don't have a cheap solution for the higher
frequency...
-Roman

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