[time-nuts] PDIP package 100 MHz decade dividers

[Richard (Rick) Karlquist]

The 74XX160/74XX162 is the decade divider that runs at maximum
clock rate for the chip.  Meaning no external feedback is
necessary to make it work at divide by 5/10.

The 74XX161/74XX163 can only divide by powers of 2 at maximum
clock rate.  You have to add feedback to divide by 5 and THAT
is what slows it down so much.  Dividing by 10 is even slower
in most logic families.

There is also 74XX190 series.

Rick N6RK

On 7/11/2020 3:00 PM, Perry Sandeen via time-nuts wrote:
> Learned List,
> On previous posts I was looking for a PDIP package 100 MHz decade divider. Reading just the front of the data sheet I thought that the 74LS161 would work. Boy, was I wrong.  Several members posted that 25 Mhz max was its limit.
> So *on the road again* (sorry Willie) I went on another search this time with the correct logic family.
> It turns out Arrow carries the 74HC161 for less that $1.
> Additionally I D/L'd the Charles Wenzel Unusual Frequency Dividers PDF and discovered a 100 MHz decade divider circuit using 1/2 of a 74HC74 in a configuration that will decade divide up to 300 MHz.
> I'm attaching a copy of the circuit for anyone interested.
> Regards,
> Perrier
> 
> 
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