Crytal oscillator - PPM

[Sarav.thegreat]

Hi,

What is meant by PPM in Crytal oscillator.

Regards,
Saravanan.K

 

[BobW]

PPM = Parts per million
It refers to the amount of drift in the output frequency.

 

[Sarav.thegreat]

Hi,

If it is +/- 25PPM then what is the drift in the output frequency?

Regards,
Saravanan.K

 

[atferrari]

Simpler and faster

Whenever you run across to ANY acronym, do this:

Go to Google text box

Type in like this: PPM acronym and see what you get. Not bad eh?

Another option is, oh surprise, PPM Wiki and see what you get. Not bad either, eh?

After that you could consider to start asking question about specific points.

Do not be lazy and save bandwith.

 

[jpanhalt]

Hi,

If it is +/- 25PPM then what is the drift in the output frequency?

Regards,
Saravanan.K

What's your center frequency? Some people find % errors easier to understand. 1 PPM = 0.0001%; so, ±25 PPM would be ±0.0025 % drift.

John

 

[Sarav.thegreat]

Hi,

Frequency : 25Mhz.

Regards,
Saravanan.K

 

[MrAl]

Here's a related and very interesting question for ya:

For a crystal spec'd at 100ppm that is 1.000000MHz at 20 deg C, what is the frequency at 30 deg C?

Also, what is the frequency at 10 deg C?

 

[ronsimpson]

For a crystal spec'd at 100ppm that is 1.000000MHz at 20 deg C, what is the frequency at 30 deg C?
Also, what is the frequency at 10 deg C?

At 30C and 10C the part will be 1mhz +/-100 ppm.

 

[MrAl]

Here's a related and very interesting question for ya:

For a crystal spec'd at 100ppm that is 1.000000MHz at 20 deg C, what is the frequency at 30 deg C?

Also, what is the frequency at 10 deg C?

Ron:

The question clearly asks for a specific frequency, not the same information that was given. Two specific temperatures were given plus the crystal tolerance, so we are asking for two specific frequencies here. There's a good reason for asking this question.

The answers will be in MHz or Hz like 1000001Hz or 999999Hz or something like that. By stating the tolerance you havent answered the question.

 

[Warpspeed]

Here's a related and very interesting question for ya:

For a crystal spec'd at 100ppm that is 1.000000MHz at 20 deg C, what is the frequency at 30 deg C?

Also, what is the frequency at 10 deg C?

An unanswerable question because the temperature coefficient is not known.

A 100ppm crystal is just the manufacturing tolerance error at 20C.
Depending on the cut, the temperature coefficient could be positive or negative by varying amounts.

As stated, that crystal will have a resonance accuracy somewhere within 100 Hz at 20C.
What it does at some different temperature is not specified.

 

[MrAl]

Hello there Warpspeed,

Ok, you win the prize
I thought it was an interesting question because the temperature variation is different than the usual ppm rating given.

Now given the temperature curve we should be able to come up with some actual values. See attached diagram.
The curve given is for an AT cut crystal and that's going to be the 1MHz crystal data.

 

[Warpspeed]

O/k, from the curve, my caffeine starved eyeballs first thing in the morning see:
10C = +7ppm
20C = +2ppm
25C = 0ppm
30C = -2ppm

But we also need to allow for the initial up to +/- 100 ppm manufacturing tolerance.

Worst case expected frequency error for this particular crystal would be:
10C = -93ppm to +107ppm
20C = -98ppm to +102ppm
25C = -100ppm to +100ppm
30C = -102ppm to +98ppm

The actual oscillation frequency could fall anywhere within those ranges.
Basically there will be up to 100Hz initial manufacturing error, and a frequency drift of 9Hz lower as the temperature rises through 20 degrees.