Crystal Oscillator: Drive Power

An old project coming back, _trying_ to bite me...

Crystal Oscillator, classic CMOS inverter configuration,

End customer claiming too much drive power.

Is there a standard (accurate) way of LAB measuring power in the crystal?

Thanks! ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Do you have a copy of the old Epson crystal data book?

--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

No. Do you have a link? ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
              Californica: Losers voting for losers.

It was a real book. I lost mine when I was laid off at Microdyne in

2001. It had several pages of iformation about measuring crystal drive and various types of crystal oscillators.

--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

"Jim Thompson" schreef in bericht news: snipped-for-privacy@4ax.com...

Don't know how to measure drive power (in a standard method). But, as this is an old project, the drive power was not too high until recently I guess. I know crystals were improved over the years and newer types require less drive power then older ones. So they can be used with 3.3V devices for instance. Standard way of connecting a new crystal type to an old oscillator design is using a series resistor.

My reasoning would be: Either the internal impedance of the inverter output is too low or the impedance of the load is too low given the configuration in which the problem arises. IMHO you cannot blame the mains power provider to have too much power available when you connect a device with too low an impedance and blow it.

petrus bitbyter

Jim won't read this, because he keeps me permanently plonked, but power dissipated in the crystal is dissipated only in the resistive (lossy) components of the crystal. And if you want to know the loss in the crystal you can get it from the Q, so what he needs to do is bang the crystal with a Dirac spike - a pulse narrower than half the period of the crystal's natural frequency - and watch how fast the subsequent ringing decays. He'd need to buffer the signal from the crystal with a high-input impedance amplifier - probably something fast with a FET- input from Burr-Brown (now Texas Instruments) though a fast CMOS inverter might be good enough.

-- Bill Sloman, Nijmegen

--
AFAIK, the only right way is to measure the crystal current with a
current probe, then to get the crystal's ESR from the data sheet and
do:

    P = I²R

United States Patent 4001675

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

That's my understanding.. typically the data sheet will only tell you the maximum motional resistance, which is okay for this purpose. With modern crystals requiring drive levels to be in the double-digit microwatts maximum, it's a constant concern.

What's going on... miniaturization making the blanks so thin that they fracture at "high" power?

I can remember opening a crystal case (cover screws), then grinding with Boraxo (or even Ajax) to get the frequency you wanted ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
              Californica: Losers voting for losers.

Yes. They can drift or even fail completely at the sort of drive levels that HC49/U crystals could stand forever.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Then you also probably remember seeing circuits that used a filament type pilot lamp in series with the crystal as a nonlinear resistor and visual indication that the local oscillator was running. Neon lamps were used as voltage regulators.

Yep, I remember the screw apart crystals in some of my old mil-surplus equipment. To increase the frequency, wet lap the crystal sheet with a fine abrasive slurry (Ajax) against a glass plate. If you went too far, rub a bit of solder against the face to increase the mass and lower the frequency a hair. Oppie

--
Yeah, quartz has its limits, and I think "fracture" is right in the
same sense that the fracture of the Tacoma narrows bridge wasn't
related to overheating as much as it was to Q.

 http://www.youtube.com/watch?v=P0Fi1VcbpAI

--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

Sounds familiar. I'll have to look in the garage, I still have some ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
"The tree of liberty must be refreshed from time to time with the
   blood of patriots and tyrants. It is it's natural manure."
            - Thomas Jefferson, November 13, 1787 

    Make the world a better place, Dispose of a Leftist Pansy

Yes, they were FT-243. I still have some, too. :)

--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.