[time-nuts] Help with TCXO

Attila Kinali attila at kinali.ch
Mon Nov 28 13:38:52 UTC 2011


On Mon, 28 Nov 2011 19:29:41 +1100
Michael Malloy <mechano at gmail.com> wrote:

> On Mon, Nov 28, 2011 at 7:14 PM, Michael Malloy <mechano at gmail.com> wrote:
> > yeah it is squaring up, but not great I have already designed the
> > circuit boards, hmm
> > maybe if i replace the 74HC04 with a 74HC14 (schmitt trigger input)
> > which I do not have
> > I did make a surface mount single gate schmitt trig after the 74HC04
> > as I knew that

You should but the HC14 infront of the HC04, not after (or simply replace it)
The HC14 is used to "clean" the output of the TCXO and make it
logic compatible. Its hysteresis will ensure that you don't have
any oscillation or other adverse efects during the "slow" rise
and fall times of the TCXO output.

> > this squares things up much better, however after the 74HC04 it goes to
> > a 74HC4040 divide by 12 counter and from that input it goes to another
> > 74HC04 into the processor
> > I am worried that the fact that the counter and the processor are 90
> > degrees out of phase clock cycle
> > if I put the single gate schmitt trig in it will bring both in phase
> > I may need to make software adjustments if this happens??

I don't see how where a phase shift of 90° occurs. If, then i'd be 180°.
Unless i misunderstood you. A schematic would be really helpfull here.


> > let me see if the 74HC14 is pin for pin compatible with 74HC04 maybe I
> > will replace with this.
> > but I do not think I have any here

They are pin compatible. The HC14 is the same as the HC04 but has
a schmitt trigger input. 


			Attila Kinali
-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin




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