Electronics > Beginners
Easy-to-use higher frequency clock generator
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radiolistener:

--- Quote from: coaxialgamer on August 23, 2019, 07:56:30 pm ---About these I2C devices, more generally: you'd typically program them using a general-purpose microcontroller, correct?
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yes


--- Quote from: coaxialgamer on August 23, 2019, 07:56:30 pm ---I saw the binary file you wrote, but assuming I settled on something else I2C, would I need to write code for that? Is there pre-existing software to do handle it? Where can I find ressources on the subject?
I'm not adverse to learning about any particular MCU, I just don't quite know where to look is all.

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I'm using complicated environment, it will be hard for you to start with it. But there is exists much more easier environment, for example you can start here: https://circuitdigest.com/microcontroller-projects/getting-started-with-stm32-development-board-stm32f103c8-using-arduino-ide

In short, you will needs to calculate XTAL (25 MHz) multiplier and divider in form of a+b/c and then send it to si5351 registers through i2c port. And also send some control registers settings in order to enable CH0 and select proper clock source. Thats it :)

For example in binary firmware that I made for 10 MHz (in attachment above) I used:
- PLL multiplier: { a=36, b=0, c=1 }
- divider { a=90, b=0, c=1 }

It leads to PLL frequency 25 MHz * (36 + 0/1) = 25 * 36 = 900 MHz

After divider we will get 900 MHz / (90 + 0/1) = 900 / 90 = 10 MHz

The output of si5351 is very clean and very stable. You will not be able to get so clean and stable signal with circuits like 555 or something like that.
tggzzz:

--- Quote from: coaxialgamer on August 23, 2019, 04:31:19 pm ---I'm working on a small project for which I need to generate a clock signal.
I'd typically use a 555 timer, but I need higher frequencies, approaching 10mhz. So that's not going to cut it.

I'm sure there are great options out there for this kind of circuit. However, I'm far from an expert in electronics, and I mostly need something that's easy to use ("programmed" externally, like a 555).
I'd really like to be able to adjust the output frequency, which is why I don't really want to use a simple crystal oscillator.
Jitter isn't too much of a concern, but I do need an LVCMOS output to work with the discrete 74 series chips I'll be using.

What options do I have here?

Again, I'm a noob here, so feel free to point out if I'm ignoring something obvious.

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One solution to that minimal spec is a 74lvc1g14 with a resistor between output and input, and a capacitor from the input to ground. Use a variable R or C to change the frequency.
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