MM74HC164 - Freq limits at 3.3V?

It is in the datasheet, page 4 in the fairchild version, or maybe you didn't ask the right question

martin

There are logic families meant for faster operation at low supply voltages, than the old 74HC parts, . For example the 74vhc family is specified down to 2.0 volts. The 74vhc164 can shift to 125MHz typical (or to 80MHz minimum), at 3.3V and 25C, according to the datasheet,

Every datasheet known to mankind will list the maximum frequency versus Vcc in the "timing" section. First and foremost before undertaking a digital design is to learn how to read datasheets. How come you don't know how to do this?

Well, Fairchild's 74hc164 datasheet doesn't say anything about operation at 3.3 volts. It says the worst-case minimum is 5 MHz at 2V, and 27 MHz at 4.5 volts, 25C. Such a huge spec variation from 5 to 27MHz makes it hard to estimate the operation at 3.3V and is one good reason to simply avoid using the hc logic family at low voltages. This is especially so when there are plenty of much better choices, like the 80MHz at 3.3V 74vhc164 I suggested.

OK, maybe it's not quite that simple. I see most distributors don't carry the 74vhc164. DigiKey and Newark don't, although Mouser does. The 74ac164 could be an alternate choice, DigiKey and Mouser have it, although Newark doesn't. The 74ac164 is spec'd at 62MHz min at 3.3V for the -40C TO +85C temp range. Hell, it'll even do 7Mhz at 1.5 volts. Now that's getting doowwn!

BTW, when it comes to finding the logic families you want in stock, it gets rather difficult if you insist on a particular IC package. For example, I like the thin ssop SMD package, TSSOP, which is both space-saving and reasonable to hand solder. But many MSI parts are not offered in that package, or if they are, they're not stocked.

Man, you must have good eyes. In my designs I need to use TSSOP a lot but really hate it when I have to swap one of these out.

It's not so bad if you're using a Metcal soldering station and have a Talon handle (which has two tips), with the right tip, TATC-502. The whole IC comes off at once in a hurry.

This family should work both 5V and 3V3 system

Yes it works, but not well.

I've used HC logic under 3V, a lot. Ok, it becomes a bit sluggish but sometimes there isn't much of a choice when you want widely available parts. For example, right now I need an 8-bit equality comparator and other stuff for bus slot and address detection. There ain't much else in stock than HC688 and the like. The other guys want to run the bus at

Guess I'll have to post a speed limit on the bus, hoping the other guys won't pelt me for that ;-)