Re: 74??00

On Fri, 11 May 2001 22:23:18 -0600 (MDT), you wrote:

>Does anybody have a table of the various designators and the specs for each?

        The TTL, and TTL-compatible, families include:

74 = standard TTL technology.
74S = Schottky TTL. Faster than standard TTL, but consumes more power.
74LS = Low-power Schottky TTL. Slower than standard TTL (anywhere from
        20-50% slower), but typically consuming about 1/4-1/3rd the power.
74H = "High-speed" TTL. Fastest TTL family, but quite power hungry.
74L = "Low Power" TTL. Lower power, and slower, than 7400 TTL, but not
        quite as low and slow as 74LS.
74F = Fairchild's "Fast" TTL. Comparable to 74S speeds, but with
        slightly lower power requirements. (Though higher than 7400 TTL)
74HCT = High-Speed CMOS TTL-level. Designed to be drop-in replacements for
        7400-series chips, but with much lower power requirements.
74AS = Advanced Schottky
74ALS = Advanced Low-Power Schottky
        (These are T.I. parts, and I'm not too familiar with them...)

        Non-TTL compatible families:
74C = CMOS. Pinout-compatible versions of their 7400-series counterparts,
        but built with 4000-series CMOS technology (i.e. s-l-o-w!) and
        having CMOS-level voltage requirements. (Basically, a way to
        encourage designers to move to CMOS technology while letting them
        continue to use the 7400-series building blocks they were already
        familiar with.)
74HC = High-Speed CMOS. Also pinout-compatible versions of 7400 chips,
        but with better CMOS technology that gets their speed up to levels
        comparable with TTL.
74AC = Advanced CMOS. Comparable to 74S-series speeds, but with CMOS
        voltage and power requirements.

74LV = Low Voltage. Designed to run on anything from 1V to 5.5V. (Built
        with CMOS technology, I think.)
74LVT = Low Voltage TTL-compatible. Same as 74LV, except that they can
        take 5-volt TTL input signals even while running at lower supply
        voltages (usually a _huge_ no-no with CMOS logic). In my
        experience, generally used as level translators between legacy
        5-volt systems and modern 3.3V core logic, though I'm sure they're
        good for more than that...

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http://lonestar.texas.net/~solarfox
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Received on Sun May 13 13:46:51 2001