How do you make a clock multiplyer?

[bboysil]

I know this is kind of a electronics question but i am curios. I know how to make a clock devider but i just don't know how tu make a clock multiplyer physicly.

 

[Lord-Ilpolazzo]

Ah! i used to wonder a lot about that. Iv never found out for sure how one really works but this is how think they work:

Idea #1
All you do is create a new clock based on the rising and falling edges of the existing clock, so you start out with say a 20Khz squarewave. You would then make a circuit that created a short pulse as it detects a rising or falling edge . Obviously the length of the pulse created as the circuit detects each edge would have to be short, i.e < 0.5 times 1/20KHz. (i.e less than the mark or space of the original squarewave.. it would probably be best to keep the mark space ratio equal actually.


____------____------____------____ - 20Khz Squarewave
---__---__---__---__---__---__---__ - 40KHz Sqaurewave


So i imagine you would repeat this for as many stages as you needed to reach the required frequency.

Idea #2
I think making a circuit to create short pulses is almost cheating as regards this problem cos if u can make higher frequency pulses why not just make that into an oscillator and use that..

so my second idea is more interesting..

What you do is have a number of clocks running at an identical frequency, say 10 * 10KHz clocks. But run them all slightly out of phase, by a very precise amount, so the master clock starts at 0degrees, and you have the remaingin 9 clocks lagging that by x degrees each like this: (il demonstrate with 3 clocks for simplicity). You then create a new clock based on, say for simplicity the rising edges of the clocks:

clock 1: --------______--------______--------______--------______

clock 2: ___--------______--------______--------______--------___

clock 3: ______--------______--------______--------______--------

result:x.----___----___----___----___----___----___----___----___

In the example above youd need to work out some logic to take in all three clocks, and toggle the output whenever a rising edge was seen on one of the inputs.

In that case of computers tho i imagine its done in a much more ingenious and complex way to that, something to do with phase locked loop type things i suspect.

 

[big_cheese]

I know this is kind of a electronics question but i am curios. I know how to make a clock devider but i just don't know how tu make a clock multiplyer physicly.

PLL is one way I know. If you know how to make a clock divider, then you'll need to learn about PFD (phase frequency detector) and a couple of other easy things, that's basically the PLL. I made one in a college project.

 

[bboysil]

I've studied about the PLL to

 

[bboysil]

I had the same ideea (the first one with the edge detector and a delay)
But still to implement this to give you from 200Mhz a 2Ghz freq, and also varible multiplyng... it's a bit out of reach
At low frequances i can design a multiplyer myself ... i think but at high freq i think this is a bit unpracticle.