The 74L72 IC


John Doran <johnd@...>
 

Howdy! I thought I'd add my two bits to the discussion of this
IC.

Miroslav was being generous--standard TTL actually requires
*ten times* as much power as L TTL! Still, I cannot imagine
that one hotter logic chip would load the 'scope's power supply
excessively. The more likely problem is that whatever drives the
74L72's inputs might not be able to handle standard TTL.

I'd bet that you could substitute an LS TTL part with no problems,
but--total bummer--the 7472 was an old design that, as far as I know,
was only made in standard, L, and H TTL variants (H TTL requires
twice the power of standard TTL).

There appear to be no direct, pin-compatible replacements
for the 74L72 in any more recent logic family. Further, it's not
just a flip-flop; it has gated J and K inputs. It seems to me that
there are only two solutions here; you must find the same part or
you must wire up an equivalent circuit (I'd use 74 HCT) on
some sort of kluge-board.

Oh, one more thing--you can use a 54L72 (military version).

-John

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