Digital IC question

[Colt45]

I'm not terribly familiar with digital ICs.

Does the clock need to be square wave, or will sine-wave suffice?


(need to drive some decade counters, and I can't remember..)

 

[pillage2001]

Originally posted by: Colt45
I'm not terribly familiar with digital ICs.

Does the clock need to be square wave, or will sine-wave suffice?


(need to drive some decade counters, and I can't remember..)

Square.

 

[helpme]

Square.

 

[Bassyhead]

yup square

 

[Demon-Xanth]

If you need to make a sine wave into a square wave, use a comparator. They do a pretty good job at it.

 

[NogginBoink]

I see no reason that the clock has to be square. The IC will have some threshold at which it will see a low-to-high transition, and one at which it will see a high-to-low transition.

But using a sine wave would be (for lack of a better word) "impure" digital electronics practice.

You may be able to use a Zener diode rather than a comparator to 'sqare out' the waveform. It'd probably be cheaper. See http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/limiter.html#c1 for an example.

 

[dighn]

Originally posted by: NogginBoink
I see no reason that the clock has to be square. The IC will have some threshold at which it will see a low-to-high transition, and one at which it will see a high-to-low transition.

But using a sine wave would be (for lack of a better word) "impure" digital electronics practice.

You may be able to use a Zener diode rather than a comparator to 'sqare out' the waveform. It'd probably be cheaper. See http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/limiter.html#c1 for an example.

or a schmitt triggar

 

[Demon-Xanth]

The problem with a sine wave is that the breakover point isn't as consistant, and you end up in the indeterminant state longer. Because of this you may have ICs trigger at different times or chatter because the transition time is too long. An example of how wide this voltage is: A 74LV00 has a high of 0.7xVcc and a low of 0.3xVcc and a switching time of about 10ns. If you stay in this region for 1us (easily possible w/ a clock in the kHz ranges) then you're likely to have it to trigger multiple times.

 

[Pepsi90919]

square wave of course

 

[Bassyhead]

Originally posted by: Demon-Xanth
The problem with a sine wave is that the breakover point isn't as consistant, and you end up in the indeterminant state longer. Because of this you may have ICs trigger at different times or chatter because the transition time is too long. An example of how wide this voltage is: A 74LV00 has a high of 0.7xVcc and a low of 0.3xVcc and a switching time of about 10ns. If you stay in this region for 1us (easily possible w/ a clock in the kHz ranges) then you're likely to have it to trigger multiple times.

thats correct

 

[Analog]

If it meets the trigger voltage requirements and does not exceed the max voltage of the chip, then a sine would work for simple counting.