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BigDumbDinosaur
 Post subject: Re: 74HC/HCT/LS
PostPosted: Mon Apr 30, 2012 3:45 am 
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GARTHWILSON wrote:
Yes, I sure wish more parts were available in 74ABT.

For the most part, it seems the 74ABT offerings are in devices where the ABT advantages (superior speed and high output drive) are best used. For example, quite a few of the standard glue logic devices are available as 74ABT parts. Digi-Key, for one, has stock for bus transceivers, flops, gates and inverters, as well as other devices (anyone for a 16 bit bidirectional line driver?). The 74ABT04 hex inverter is interesting, with a typical propagation time of 2.2 nanoseconds.

The only downside is few 74ABT devices are available in DIP packages. Many are available in SO packages with 50 mil pin spacing, a dimension that is within the realm of manual soldering. I can manually solder an SOJ package and I'm a decrepit dinosaur of uncertain cranial capacity. :lol:

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brain
PostPosted: Fri Jun 01, 2012 12:20 am 
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Does ABT and AC have the ringing issues of AS?

Jim
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BigDumbDinosaur
PostPosted: Fri Jun 01, 2012 1:11 am 
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brain wrote:
Does ABT and AC have the ringing issues of AS?

Jim

From my observations, AC has less trouble with ringing than AS, ABT a lot less.

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GARTHWILSON
PostPosted: Fri Jun 01, 2012 1:36 am 
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brain wrote:
Does ABT and AC have the ringing issues of AS?

Fairchild's ap. note AN640, "Understanding and Minimizing Ground Bounce," at https://www.onsemi.com/pub/Collateral/AN-640.pdf.pdf is a good one for understanding ground bounce and decoupling and mostly explains the ringing issue.  Ringing is not a fault of the logic family but rather the construction method not being adequate for the slew rates.  Slower slew rates (generally from slower logic) let you get by with sloppier construction.  There is a little bit that can be done in the logic output to reduce the problem while keeping a fast slew rate, by slowing down only the beginning and end of the slew, as shown in Fairchild's ap. note AN-680, "Dynamic Threshold for Advanced CMOS Logic," at https://www.onsemi.com/pub/Collateral/AN-680-D.PDF . Section 9 of my 6502 primer, "Construction: Avoiding AC-Performance Problems" at http://wilsonminesco.com/6502primer/construction.html has a self-explanatory title, and of course don't forget our sticky topic "Techniques for reliable high-speed digital circuits" at viewtopic.php?f=4&t=2029 .

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