[SI-LIST] Re: ppm(parts per million)-Crystal OSC
- From: Dudi Tash <dudi@xxxxxxxxxxxxxxxxx>
- To: "Wolfgang.Maichen@xxxxxxxxxxxx" <Wolfgang.Maichen@xxxxxxxxxxxx>, "balaseven@xxxxxxxxx" <balaseven@xxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Wed, 14 Dec 2011 12:36:26 +0200
Great explanation.
Putting things simpler, ppm is just another case of showing tolerance in
percentage, like dbs are used to show another way of ratio
David Tash
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Wolfgang.Maichen@xxxxxxxxxxxx
Sent: Wednesday, December 14, 2011 12:27 PM
To: balaseven@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: ppm(parts per million)-Crystal OSC
Hello Bala,
these two specs have very different meanings:
Frequency in Hz gives the nominal (expected) frequency of the oscillator. E.g.
100 MHz.
The tolerance in ppm (parts per million) gives the possible deviation of any
particular oscillator from the nominal frequency. Typically this is a
combination of manufacturing tolerances and environmental influences
(temperature, aging). E.g. 10ppm
So if you by an oscillator rated at 100 MHz and 10 ppm that means the actual
output frequency may lie anywhere between 100MHz *(1 +/- 10*1E-6), i.e. 99.999
MHz and 100.001 MHz.
How much frequency deviation your system can deal with depends on a variety of
factors, there is no general answer.
Regards,
Wolfgang
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of bala
Sent: Wednesday, December 14, 2011 11:17 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] ppm(parts per million)-Crystal OSC
Hi all,
I have a little confusion on PPM vs frequency of Crystal Oscillators.How
important is the term 'ppm' than frequency.Why all the datasheets have both
units,ppm and Hz.Please clarify,Also how much important is the value of ppm on
the Signal integrity side,if any.Thanks for your time.
--
bala
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