On Tue, 18 Jun 2013 10:52:24 -0400
paul swed <paulsw...@gmail.com> wrote:
> Interesting the HC will work all the way down to 2.2V so everything can be
> run from 3 Volts.
I don't have a spec sheet at hand, but are HC types speced down to 2.2V?
I thought it was something around 3V
> No idea as to the effect of the xtal oscillator maybe the 3.9 M R needs to
> be changed.
Probably not. the 3.9M resistor is to give the oscillator circuit
(which is an unbuffered inverter) a DC bias. Its value is usually not
critical.
> It also appears that the HC chip may doing the lions share of current
> consumption. Spec sheet says up to 20 Ma. Hard to believe actually.
As long as it's mA not MA, it is indeed believable ;-)
HC used quite a bit of current. Especially when toggling at high speed
(where as high speed is to be seen relative to the 70s when these chips
were designed).
> As for driving lengths of wire over distance it needs to be a buffer chip.
> 74hc244. But that seems like serious overkill it can drive 20 ma per port.
If it's just a single signal, why not use a pair of digital mosfets like
FDV302P/FDV303N? These can drive a big load (680mA speced, with good cooling)
and are can be interfaced with 3V logic.
Attila Kinali
--
The people on 4chan are like brilliant psychologists
who also happen to be insane and gross.
-- unknown
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