[time-nuts] Fwd: 10MHz to 80MHz frequency multiplier suggestions

Tijd Dingen tijddingen at yahoo.com
Sun Feb 6 16:06:15 UTC 2011


damn send button....

Additionally, the definition as used in this appnote from Vectron:

http://www.vectron.com/products/literature_library/absolute_pull_range.pdf


Definition

APR is the minimum guaranteed amount the VCXO can be varied, about the center 
frequency (fo). It 
accounts for degradation’s including temperature (0 to 70 or -40 to 85°C), aging 
 (20 years, 40°C), power 
supply variations (10%) and load variations.
APR = (Pull range) - (degradations due to temperature+aging+power supply+load)


So at least 10 years of aging within the spec seems a safe assumption, and quite 
possibly it's 20 years of aging at 40 degrees within the spec.

regards,
Fred

----- Original Message ----
From: Tijd Dingen <tijddingen at yahoo.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Sun, February 6, 2011 4:47:20 PM
Subject: Re: [time-nuts] Fwd: 10MHz to 80MHz frequency multiplier suggestions




> > Possibly you mean the CVS575 datasheet does not have any aging specs.... The
> >  datasheet for the CVHD-950 specifies aging as "<3ppm 1st/yr, <1ppm
> > thereafter"  which is good enough for me. So it's now on the shopping list. 

> No, what I meant was that the data sheets didn't have any total lifetime 
> specs.

> If the aging is 1 ppm per year and the APR says 50 ppm, how many years does 
> that cover?

> Suppose they used 10 years.  If you are designing for  20 years then you have 
> to subtract another 10 years of aging so you only get an APR of 40 ppm.

> Hopefully, their APR spec covers an infinite lifetime.  If so, there is a 
> hidden spec, something like aging gets lower with age so the tail after 10 
> years is lost in the noise of other stuff.  But I didn't find any hints like 
> that in any of the app-notes I looked at.  (and I'm a suspicious old-fart, 
> aka nit-picker when reading data sheets)


Well, there are some hints in their appnote on APR: 
http://www.crystek.com/microwave/appnotes/AbsolutePullingRangeAPR.pdf


"The minimum pulling range of a VCXO is determined by:

Minimum VCXO Pull = Total VCXO errors + APR Desired"


Given how they wrote this appnote from the perspective of how a VCXO 
manufacturer gets their APR specs, you could rewrite that as:

APR spec = Minimum total VCXO Pullability - Total VCXO errors (*)

(*) where the errors include:

1) Frequency vs. temperature
2) Aging vs. time
3) Center frequency calibration
4) Load and Supply change variation


At least that's how I read it. I could easily be wrong. :P

And just to be sure, check for example this IDT appnote: 
http://www.idt.com/products/getdoc.cfm?docID=18723561

"Definition of APR:

APR - The guaranteed plus and minus frequency deviation of a VCXO from the 
nominal frequency when the control voltage is set to the maximum and minimum 
value. It is guaranteed over manufacturing tolerances, supply voltage, perating 
temperature and aging.

APR is calculated by subtracting the Total Pull Range from the Total Stability 
of the VCXO. The Total Pull Range is the maximum variation in VCXO frequency 
over changes in control voltage under constant supply voltage and temperature. 
Total Stability is the variation in VCXO frequency when the control voltage is 
held at the nominal value over changes in manufacturing tolerances, supply 
voltage, operating temperature and aging. This difference results in the 
frequency variation that can be guaranteed due to the control voltage 
independent of all other conditions and variations."

Both pdf's do not explicitly state it, but it looks suspiciously much like they 
are using that "10 years Aging Tolerance" in the APR definition.

I did check MIL-0-55310, but that didn't give me any clear definition either. So 


my working assumption for now is that the APR is calculated using a 10 years 
aging tolerance.

regards,
Fred



      

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