[time-nuts] low power divide by 5

ed breya eb at telight.com
Thu Jul 2 18:37:37 UTC 2020


It's been fun reminiscing about all these dividers and techniques, but 
getting back to the OP, the original search was for a divide by 5 with 
"low power" and operation from 5 to possibly 3.3V, and clocking properly 
at 50 MHz. One would assume also minimal size and complexity, and low cost.

One piece of info that is missing, is how many of these are needed. If 
it's a one-off situation, that's way different from mass production and 
assured parts availability. If only one or a few are needed, then I'd 
contend that the 74AC390 is the way to go. It definitely will work at 
the lower end of the supply range, and is the simplest in parts count - 
one piece, and no doubts about external prop delays that would be 
associated with getting other types to divide by 5.

If there are truly lots of NOS ones out there, it should possible to 
just buy a bunch for all anticipated needs. I can't imagine they would 
be very expensive, except for the issues of volume versus transaction 
cost. I've never tried to buy old parts from these kinds of 
distributors, but I would imagine there would be minimum order 
requirements or fixed cost. So, getting one piece might cost $100, while 
getting a hundred pieces may be $110, and so on. There's no harm in 
asking and negotiating.

Ed





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