Digital Logic IC family

The data sheet will tell you!

Or the part name...

HC: high speed CMOS HCT: high speed CMOS with TTL-compatible thresholds

etc. ...Jim Thompson

The "family" is a more or less convenient shorthand for a whole handful of characteristics. For many components a portion of the part number is used to designate the family, e.g., 74LS00 versus 74HCT00. If a component's characteristics are broadly similar to a recognized family designation then the datasheet will usually say so.

When you're mixing things like processors, gates, and interface chips, though, one really has to look at the characteristics of the individual connections. For example, is the minimum guaranteed output logic high voltage adequate for the maximum guaranteed threshold required to be recognized as a logic-high state? With an adequate noise margin?

There's really no shortcut. Also, don't rely on "typical" values.

TTL vs. CMOS is easy. The first way to tell is to take a guess at the age of the part -- if it's less than 20 or 30 years old, it's CMOS of some sort. The second way is to look at the guaranteed output voltages: TTL will only promise to pull down to something like 0.2V (one saturated transistor drop), and up to 2.4V or so on a 5V part (because the TTL output stage is a totem-pole arrangement that needs a few diode drops to do it's job).

Beyond that, the 'families' that you cite are specific to 74xx series logic. Each has particular speed and voltage characteristics, but these aren't necessarily replicated in someone's processor or whatnot.

So you're left with earning your pay as a circuit designer: you plow through all the pertinent data sheets matching guaranteed output voltages with guaranteed input voltages, and making sure that one company's "3.3V compatible input" really matches some other company's

Make sure clocks line up, too, and don't forget all the timing parameters.

Thanks for all the responses. In case of 74xx series it is mentioned in the datasheet. What about micro controllers, processors, codecs etc. For eaxmple, I looked at AD1955 DAC (Analog Devices) and I.MX28 (Freescale) datasheets and no where it says the part belongs to which family.

-Mark.

You may be confusing "family" with "technology". Like their human counterparts, members of a device family share many common characteristics and are usually designed to be so. Examples of such characteristics are power supply requirements, speed, switching threshold, output capability, etc. OTOH, devices made with the same technology do not necessarily have such common characteristics. For example, CMOS technology is employed in making the 4000, 4500, 74HC and 74HCT families as well as microprocessors, microcontrollers, etc. Some devices may not have enough close kin to be regarded as belonging to a family. A family is usually made with the same technology, but devices made with the same technology do not always belong to the same family.