XO controlled 480Hz Oscillator

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Function of pin #3 Fairchild Q14 NXP Q13 ON Q14 ST Q14 TI QN

Best regards, Spehro Pefhany

Thanks, John. The pain in the butt is that different datasheets have different designations. The one from TI that Chris posted goes to Q14.

Your post is great, because it brought that to light. I didn't know that, :-( until I saw your post :-)

Ed

Yes, I am in North America. I need the deck to be portable, so working off of mains is not usually going to be an option. The capstan motor does run on 60Hz 120VAC, but I would only be able to shoot footage where I have mains. The crystal/fork is for the inverter as the tape transport is run by a sync motor with a sprocketed capstan (the tape is perforated).

Regards, Chris Maness

Digikey has 60 KHz crystals. Divide by 5 three times, then by 2 for your 480 Hz. Or just divide by 1000 and low pass filter it before amplfing it to drive the 60Hz motor.

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I ordered some CD4060B's (25 for $3 on ebay). I am going to order some 3.9Mhz crystals and divide by 2^13 on the 4060. Should be very easy.

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All you need to know is:

To know that the code I gave was the best that can be done.

One of the guys in this thread sent me an Application Guide:

This is a very interesting read. However, the information here does not seem to agree with the design suggestion for the crystal network in the data sheet for the 6040B. Fig. 13 (

Any guidance would be appreciated.

Thanks, Chris Maness KQ6UP

Yes, but input (and stray capacitance should also be taken into account).

The data sheet is incorrect on this point.

It's limited by the maximum crystal power dissipation and series resistance of the crystal, crystal frequency, load capacitance, supply voltage. HC-49 ~4MHz crystals are usually good for 1-2mW, some of the SMD parts or kHz tuning fork types, down in the microwatts.

Given a physically larger crystal that can take 1-2mW of drive, you can probably forget about Rs, use 22-27pF for the caps and 1M for the parallel resistor. More caution is called for at high supply voltage.

Should I use 25pF trimmers so that I can dial in the freq.

Thanks, Chris

Your application cares about the last 0.01%? You can't 'pull' a normal quartz crystal much.

kr

tion

Yes, my application does depend on the freq. being spot on. A little off, and my film dialog will look like a bad kung foo flick.

You can't 'pull' a normal

I am getting a freq. counter in a couple of days. It is supposed to be good within .3Hz. I was thinking that with the trimmer, I could account for a unknown, stray capacitance.

Just a thought. What do you think?

Regards, Chris

It will always be a bit off, the engineering question is how much is acceptable.

ion

You may be better off placing a 100pF trimmer in series with the crystal. The C1 / C2 ratio doesn't want to be too far from 1.0 since it controls the swing at both ends.

The DC feedback resistor doesn't matter much so long as it is large enough. The crystal drive resistor needs to be low enough to get the crystal to start beyond that, you don't really use it to set the power level. The capacitors do more to set that than the resistor.

If you find that the oscillator runs slow, you may want to replace or parallel the crystal drive resistor with a small capacitor. This is not often explained in the data sheets and app notes but if the delay through the inverter of the 4060 is too large, the oscillator will want to run at a lower frequency. You fix this by adding a phase lead with the capacitor.

When ordering a frequency for a specific frequency, specify also the load capacitance or specify the frequency slightly (a few dozen ppm) above the desired frequency and pull it down to the desired frequency with a parallel capacitor. Pulling upwards is harder with a series inductance.

Overtone crystals (typically above 20 MHz) have a more limited pulling range.

Or if he really needs ppm-level accuracy/stability or better, replace the crystal with a TCXO or VCTCXO (or even OCXO if warm-up time is not important).

Eg.

or

Specs are important, because the 4060 apparently won't work with off-the-shelf frequencies, wheras the PIC or some equivalant combination of HCMOS could.

Related to the inverse of the square of the overtone, so 1/9 range for a 3rd overtone.

Best regards, Spehro Pefhany