One other item, aside from speed to be considered when using this part, is
the current it will sink. The LS variety was slower, basically because it
used a slower technology. The 8T97 used essentially the same technology
internally as the SCHOTTKY parts the various vendors sold, but it had
stiffer outputs, i.e. could sink/source more current. Almost any part which
was as fast and would source/sink as much current, will generally bring
about the same behavior in the rest of the circuit. If the edges become too
steep, as you might see in the form of too much ringing or
overshoot/undershoot, soldering little 1/8-watt resistors in series with the
outputs will help. I'd say start with 47 ohms and go as far to the smaller
side of that as you like. Fairchild actually made a version of their
"F-series" logic with 33-ohm resistors built in to minimize problems from
both ground bounce and output edges being too steep. One other thing that
helps somewhat is to solder a small (<.001uF) high-frequency cap between
power and ground on the IC, straight across the back. The leads are long,
but it will maintain enough local storage to help with the ground bounce.
Dick
-----Original Message-----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Monday, June 21, 1999 7:53 PM
Subject: Re: N8T97N IC, what is it?
>>
>> Jim:
>>
>> The 8T97 was also recently discontinued by Jameco.
>>
>> How does the propogation delay compare to the LS367? Tony said that
the
>> 8T97 has an 8us delay. ISTR that the reason to use the 8T97 was that it
had
>> a shorter delay.
>
>
>Yes, you're right. The same Signetics data book lists the 74LS367 as
>having a typical propagation delay of 10ns. Incidentally, if I claimed
>8us for the 8T97, that was a typo, I meant 8ns, of course.
>
>Anyway, the 74F367 (I looked in the Philips databook) claims a typical
>delay of 5ns, so that should easily replace the 8T97 (provided decoupling
>an layout is OK - these FAST chips like to cause ground-bounce, etc).
>
>
>-tony
>
Received on Tue Jun 22 1999 - 18:44:36 BST