Help about square waveform generation!

Thread Starter

davidgrohl

Joined Jun 18, 2014
2
Hi all,
I'm a new forum user. I need your help. I would to generate a square waveform @1MHz or less more. I need to add this functionality to a board equipped with a STM32F107 CPU. I'm finishing board schematics but I can't find a way to generate a good waveform. The output voltage has to go from 0V to 3.0V. I try to search for a DAC but it seems to be too slow for what I need. Can you give me some indications about that.
Thanks a lot.

P.s. Sorry for my english :)
 

Thread Starter

davidgrohl

Joined Jun 18, 2014
2
Oscillator is 3.3V output. I need 3.0V
I need a programmable output too. My square generation should be stoppable. Any suggestions?
 

Papabravo

Joined Feb 24, 2006
21,157
Sure. Read the specs carefully and note that they will work over a range of Vcc. Then look for an oscillator with an enable pin. So the four pins would be Vcc, GND, ENABLE, and CLKOUT.

http://www.aextal.com/AE331.pdf

Looking carefully, I see that Vdd can be in the range of 3.0V to 3.6V. Almost all parts are designed this way for a reason. It is very hard to control Vcc to an exact, to 2 decimal places, value.

PS. Give me some credit for reading your original post and seeing that you needed a 3V supply.
 

BobTPH

Joined Jun 5, 2013
8,804
And with a 3.0V supply the oscillator will be able to drive 3.0V into any load? Or does it also depend on load impedance?

Bob
 

THE_RB

Joined Feb 11, 2008
5,438
Someone has to ask...

WHY do you need to make the micro generate a squarewave of 1MHz with some adjustability? What will that connect to?

If you provide more information we can suggest more (and better) options. :)
 

Papabravo

Joined Feb 24, 2006
21,157
And with a 3.0V supply the oscillator will be able to drive 3.0V into any load? Or does it also depend on load impedance?

Bob
Well I believe that a CMOS push pull driver will drive more loads, especially capacitive loads, than anything else I can imagine, but let's consult the datasheet.

It will drive 5 TTL loads @ 1.6 mA per TTL load or 8 mA, or 15 pf of capacitive load with 6 ns rise and fall times.
 
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