Re: TTL specs

On Sat, 29 Sep 2001 18:36:26 -0500, you wrote:

>Once again I may be in over my head, this time with TTL ICs. On the Red
>Baron board I've been working on, someone has substituted a DM7411N for the
>74LS11 at J9. Philips or Signetics apparently made these chips, and the data
>sheet that covers both is at:
>http://www.freetradezone.com/dc_images/41/61/D0194161.pdf.
>The 7411 seems just a little slower than the 74LS11, and takes a higher
>supply current. Is the DM7411N an adequate sub for the 74LS11?

        A great deal depends on the circuit it's going into. (Are you sure
you're looking at the right specs, BTW? My databooks show the opposite,
speedwise; a "standard TTL" 7411 is a bit faster than a 74LS11, but with
higher current draw.) While you can _usually_ get away with this
substitution, it is possible to get into a race condition if another chip
down the line is expecting one signal from the 74LS11 and one from some
other gate to arrive simultaneously.

        Personally, I try to avoid mixing logic families if at all possible. :)
Nine times out of ten, it won't matter, but that tenth time will have you
tearing your hair out trying to figure out why it's not working...
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But you're about to learn."
                --(Leonard Pitts jr., newspaper columnist, Sept. 12th, 2001)
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solarfox@DON'TMESSWITHtexas.net (Gary Akins jr.)
http://solarfox.home.texas.net/
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Received on Sat Sep 29 17:39:01 2001