If you put a scope on the circuit you may see that this chip is in
oscillation. Did you use bypass capacitors?  See if it is oscillating. That
would cause lager current draw.


On Thu, Aug 29, 2019 at 9:14 PM Jason White <
whitewaterssoftwareinfo@gmail.com> wrote:

> Russell that is pretty clever, I am half tempted to give it a try on one =
of
> my existing prototype boards just to see if it works. The next revision
> will probably get Schmitt trigger ICs since this is (will be) a safety
> sensitive application.
>
>
> On Thursday, August 29, 2019, RussellMc <apptechnz@gmail.com> wrote:
>
> > On Fri, 30 Aug 2019 at 09:05, Jason White <
> > whitewaterssoftwareinfo@gmail.com>
> > wrote:
> >
> > > My application is space and power constrained. Is there a logic gate
> that
> >
> > does not exhibit this behavior? (100uA in the undefined would be much
> more
> > acceptable than 45mA) Maybe a schmitt trigger would be designed to
> > >
> > >
> > > A Schmitt triggered gate is the obvious solution, as you and others
> have
> > noted.
> > Below I describe an extremely 'naughty' concept which may be able to be
> > made to work deep-ending on overall situation.
> > This arrangement
> >
> >      - may not work at all
> >      - may be an utter disaster
> >      - may be able to be made to work extremely well
> >
> > Odds are the naughtiness factor exceeds the levels acceptable in a real
> > world design :-).
> >
> > "" Solution """: Add a 'suitably sized' resistor in the IC's Vdd line.
> >
> > Greatly increased current drain will lower the IC's Vdd thus increasing
> the
> > relative voltage of the inputs relative to the IC.
> > Reduction of current drain will restore the voltages so there is a
> > potential for oscillation depending on time constants.
> >
> > (This "works", if at all, on rising input waveforms.
> > A resistor in the Vss line will achieve a similar result with falling
> > inputs.
> > Both at once (probably) don't work for equal sized resistors. Assymetri=
c
> > sizing may work in both directions in some cases but, by then magic is
> > probably safer).
> >
> > I have never tried this with an IC.
> > But I have successfully added hysteresis in a transistor based circuit =
by
> > adding a small resistor in a current path and using the small pedestal =
to
> > raise a switching voltage level elsewhere. Not a formal Schmitt per se.
> In
> > that case the solution was 'almost elegant' rather than 'naughty' and
> > produced superb results with astonishingly small levels of hysteresis f=
or
> > the results achieved. (ie calculation suggested that the level that
> worked
> > was far smaller than would be expected to be effective.
> >
> >
> >  Russell
> > --
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> >
>
>
> --
> Jason White
> --
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