I've 10 4 MHZ crystal oscillators. I need a 16MHZ clock signal. Can I connect multiple 4MHZ oscillators somehow (serial, parallel) to get 16MHZ?
Electronic – How to connect 4MHZ crystal oscillator to get 16MHZ
crystalmicrocontrolleroscillator
Related Solutions
You are interested in the relative error and/or stability, which is unaffected by any division. So, other things being equal, take the lowest ppm clock source for the best accuracy.
If 50 ppm is enough for you, I would choose the crystal for board space and price.
For better accuracy you could consider a better quality (tuned) crystal oscillator. Same physical format as a regular oscillator (14-pin DIP size), but higher price (~ $20).
Not sure if you are still around or gave up, but in order to create a stable VCXO clock locked to the PAL chroma burst, you need a few timing signals like a "sandcastle" window detector to sample and hold the phase error during this period for the PLL to work.
So use this chip to get your clock and you are good to go.
Since a crystal has an extremely narrow bandwidth (BW) of 1/3000 of the centre frequency, that BW (~1KHz) will determine the best case low pass response delay and lock up time of the Xtal, however once many colour bursts are received or around 10mS of accumulated bursts) , it will stay in sync until the next horizontal line, so that only minor phase corrections can be done during the burst.
It is extremely difficult (but not impossible) to make a PLL lock up in one cycle and then be stable until the next burst. It would require precise measurement of frequency and phase with a 100x clock to get within 1%. using the horizontal sync with 2nS stability. The Horz Sync acts as a freq reference for another PLL loop from the same VCXO with less than 1ppm error and very low phase noise, which sounds easy, but is not cheap.
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Best Answer
No, connecting them in series or parallel won't get you a higher frequency.
What you're looking for is a Phase Locked Loop or PLL. Here's a block diagram:
A Voltage Controlled Oscillator (VCO) generates the output frequency. This signal is divided and then compared to the input frequency in the Phase Detector. If the two frequencies aren't the same, the output frequency is adjusted. This is called a feedback loop: you feed the output frequency back to adjust it.
The Pre Divider allows you to multiply the input frequency with a floating point number. For example, when you want to multiply by 2.5=5/2, you first divide the input frequency by 2 and then multiply by 5.
There are ICs available that have a PLL implemented, like the LM565. On page 10 of the datasheet a typical application circuit for a ×10 multiplier is given:
By changing the voltage divider (the external IC) you can make it a ×4 multiplier.
Implementing a PLL will cost some effort and space - consider buying a new crystal.