[time-nuts] low power divide by 5

[Richard (Rick) Karlquist]

The sum of propagation delay (~15 ns) and setup time (~5 ns)
in the 74AC161 gives just enough time to operate at 50 MHz,
based on the data sheet.  Of course, at room temp, the chip
will beat the data sheet by an undetermined margin.

The fact that the clock frequency is specified at 103 MHz
applies only to a free running configuration (divide by
2, 4, 8, or 16 only) and is irrelevant to dividing by 5.
If only there were a 74HC160 version.  Actually, you
can get them from Rochester Electronics ... but you have
to buy $250 worth minimum.

As noted, my favorite trick of connecting pin 11 to pin 9
is no help in this logic family because they finally did
the carry out correctly.

Rick N6RK

On 7/2/2020 7:03 AM, ew via time-nuts wrote:
> 161 and 163 are candidates. Back in the early 70's my favorite for my counter work  was the 74S112 dual JK. So I went to DigiKey to check on CD74AC112 they have in stock so with two of those along with an AND gate you can make as many divide as 5 as you need.  Just like the S112 it clocks over 100 MHz!
> Bert Kehren
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