[time-nuts] homebrew counter new board test result

[Attila Kinali]

On Tue, 24 Feb 2015 14:43:10 +0800
Li Ang <lllaaa at gmail.com> wrote:

>     I saw people talking about using 74AC to square the signal, what's the
> difference between 74LVC and 74AC? 74AC is not easy to get.

These are different families of chip production. You can see the 74HCxx as
the grandfather, 74ACxx as the father and the 74LVCxx as the son.

IIRC the AC (Advanced CMOS) was introduced in the 80s. The process
which they were produced got superseeded and also the voltage levels
went down. The LVC (Low Voltage CMOS) and LVX families are the current
choice for logic gates. The main difference is that the node size (those nm
measures people boast with, when they talk about chips these days) went
down and with that the threshold voltage of the FETs and the maximum
voltage the chips can withstand. Of course there are differences in the
timing specs as well.

TI's Logic Guide[1] and their Logic Migration Guide[2] contain
additional information.


				Attila Kinali


[1] http://www.ti.com/lit/sg/sdyu001aa/sdyu001aa.pdf
[2] http://www.ti.com/lit/ml/scyb032/scyb032.pdf

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson